9th Physics Full book

UNIT 1

PHYSICAL QUANTITIES AND

MEASUREMENT

Q1. Define science. 09101001

Q2. Define physics and explain its branches. (Board 2015) 09101002

Q3. Write the importance of physics in our daily life. 09101003

(OR)

Describe the role of Physics in Science and Technology.

Q4. What is the harmful effect of scientific invention on environments? 09101004

Q5. Define physical quantities. Also write its types. (OR) What is difference between base and derived quantities? 09101005

Q6. What is International system of units? (OR) What role SI Units have played in the development of Science? (Board 2016) 09101006

Q7. What are base units and derived units? OR What is the difference between base and derived Units? (Board 2014) 09101007

Q8. Define prefixes and give example. (Board 2016) 09101008

Q9. Define Scientific Notation and give examples. 09101009

Q10. What are measuring instruments? Explain meter rule and measuring tape.

(Board 2015) 09101010

Q11. What is meant by vernier callipers? Write its construction and working. 09101011

Q12. How can we take reading on Vernier Callipers? 09101012

Q13. Define “SCREW GAUGE” and write its construction and working. 09101013

Q14. What are mass measuring instruments? 09101014

Q15. What is physical balance? Write its construction and working. 09101015

Q16. What is the Lever Balance? 09101016

Q17. What do you know about Electronic Balance? 09101017

Q18. Show by an example which one is the most accurate balance? 09101018

Q19. What is meant by Stopwatch? Write its types and their working. (Board 2014) 09101019

OR How can a mechanical and digital stop watch be used?

Q20. What is measuring cylinder? Explain. 09101020

Q21. How can we use a measuring cylinder? 09101021

Q22. How can we measure the volume of an irregular shaped solid object? 09101022

Q23. Define Significant Figures and upon what factors does accuracy of physical quantity depend? 09101023

Q24. What are the rules to find the significant figures in a measurement? (Board 2016) 09101024

Multiple Choice Questions

Encircle the correct answer from the given choices:

Exercise MCQs

1. The number of base units in SI are

(a)3 (b) 6 (Board 2013) 09101025

2. Which one of the following unit is not a derived unit? (Board 2014) 09101026

(a) pascal (b) kilogramme

3. Amount of a substance in terms of numbers is measured in: (Board 2016) 09101027

(a) gram (b) kilogramme

4. An interval of 200 µs equivalent to: (Board 2016) 09101028

(a) 0.2s (b) 0.02s

5. Which one of the following is the smallest quantity? (Board 2014) 09101029

(a) 0.01g (b) 2mg

6. Which instrument is most suitable to measure the internal diameter of a test tube? 09101030

(a) Metre rule

(b)Vernier Callipers

(d) Screw Gauge

7. A student claimed the diameter of a wire as 1.032 cm using Vernier callipers. Upto what extent do you agree with it?

(a) 1 cm (b) 1.0 cm 09101031

8. A measuring cylinder is used to measure.

(Board 2016) 09101032

(a) mass (b) area

9. A student noted the thickness of glass sheet using screw gauge. On the main scale it reads 3 divisions while 8^th division on the circular scale coincides with index line. Its thickness is. 09101033

(a) 3.8 cm (b) 3.08 mm

10.Significant figures in an expression are.

(a) all the digits 09101034

(b) all accurately known digits

(d) all the accurately known digits and all the doubtful digits

Additional MCQs

11. 1micro(µ)= 09101035

(a) 10^-3 (b) 10^-6

12. 1nm have meters. 09101036

(a) 10^-3 m (b) 10^-6 m

13. In measurement 1.032 numbers of significant figure are 09101037

(a) 1 (b) 2

14. The unit of electric current is. 09101038

(a) candela (b) metre

15. Andromeda is one of the billions of galaxies of known. 09101039

(a) star (b) asteroid

16. The study of the structure and properties of atom is called. 09101040

(a) Electricity

(b) nuclear physics

(d) atomic physics

17. The eleventh general conference was held in Paris in: 09101041

(a) 1959 (b) 1961

18.The unit of electric charge is. 09101042

(a) coulomb (b) ampere

19.The least count of Vernier calipers is:

(Board 2015) 09101043

(a) .01mm (b)0.1mm

(c).001mm (d).01m

20. The least count of screw gauge is

(a) .01mm (b) 0.1mm 09101044

21.A thimble of circular scale consists of equal division. 09101045

(a)100 (b)10

22.In screw gauge if zero of circular scale is behind the index line is called error. 09101046

(a) positive (b) zero

23. The number 275.00 consists of significant figures. 09101047

(a) 3 (b) 5

24. Science is that word which is derived by Latin word 09101048

(a) scient (b) scientis

25. The number .00580 in scientific notation is: 09101049

(a) 5.80×10⁵ (b) 5.80×10^-4

26. The unit of force is 09101050

(a) newton (b) m³ (Board 2014)

27. The study of internal structure of Earth is called: (Board 2014) 09101051

(a) Atomic physics (b) Plasma physics

28. One cubic metre is equal to. (Board 2014)

(a)100litre (b) 1000litre 09101052

29. The base quantity is: (Board 2013)

(a) mass (b) volume 09101053

30. The smallest division that can be taken by a meter rule is: 09101054

(a) 1cm (b) 1mm

31. Least count of digital vernier callipers is:

(a) 0.01cm (b) 0.01mm 09101055

32. For balancing the beam balance, pointer must be at: 09101056

(a) zero (b) extreme position

33. Least count of physical balance is:

(a) 0.001g (b) 0.01g 09101057

34. Least count of electronic balance is:

(a) 0.001g (b) 0.01g 09101058

35. Least count of digital stop watch is:

(a) 0.01 sec (b) 0.1sec 09101059

36. Mechanical stop watch can measure up to part of a second: 09101060

(a) 1 (b) 1/10^th

37. Meniscus of which liquid curves upward: 09101061

(a) Water (b) Honey

38. While rounding the numbers if last digit is 5, then: 09101062

(a) It is simply dropped

(b) The digit on its left is increased by 1

number.

(d) It remain same

39. The value we get after rounding 1.47 is:

(a) 1.4 (b) 1.5 09101063

40. In vernier callipers if zero line of vernier scale is on the left side of zero of the main scale then the error will be: 09101064

(a) positive (b) negative

41. 1mm = m: 09101065

(a) 10³ (b) 10^-2

42. A car is made on the principles of

(a) Mechanics 09101066

(b) Electricity

(d) Electronics

43. A refrigerator is based on the principles of: 09101067

(a) mechanics (b) Electricity

44. In the nineteenth century, physical sciences were divided into distinct discipline: 09101068

(a) 4 (b) 5

45. A physical quantity possesses characteristics: 09101069

(a) 2 (b) 3

46. The word science means: 09101070

(a) Intelligence (b) Nature

47. The scientific notation of number 0.00235 is expressed as: 09101071

(a) (b)

48. Significant figures in 0.0010 are:

(a) two (b) one 09101072

49. In prefix form, 0.000001 would be expressed as: 09101073

(a) 0.1mm (b) 0.01mm

50. Prefix naming as centi has a factor of:

(a) (b) 09101074

51. In reading 27.5 first two digits are accurate while third one is: 09101075

(a) accurate (b) correct

52. Standards of physical quantities were established in: 09101076

(a) 1910 (b) 1920

53. Prefix naming as Giga has a symbol:

(a) M (b) G 09101077

54. According to SI-units, intensity of light is measured in: 09101078

(a) meters (b) moles

Exercise Question Answers

Q1.2 What is the difference between base quantities and drive quantities. Give three examples in each case. 09101079

Q1.3 Pick out the base units in the following: 09101080

Q1.4. Find the base quantities involved in each of the following derived quantities:

(a)speed (b) volume 09101081

(c)force (d) work

Q1.5 Estimate your age in seconds. (Board 2014) 09101082

Q1.6 What role SI units have played in the development of science? (Board 2013) 09101083

Q1.7 What is meant by vernier constant? (Board 2014, 15) 09101084

Q1.8 What do you understand by the zero error of a measuring instrument?

(Board 2014) 09101085

Q1.9 Why is the use of zero error necessary in a measuring instrument?

(Board 2013) 09101086

Q1.10 What is a stopwatch? What is the least count of a mechanical stopwatch you have used in the laboratories? 09101087

Q1.11 Why do we need to measure extremely small interval of time? 09101088

Q1.12 What is meant by significant figures of a measurement? 09101089

Q1.13 How is precision related to the significant figures in a measured quantity?

09101090

Additional Answer Questions

Q14. What do you know about Andromeda?

09101091

Q15. Change 16 years age into seconds. (Board 2015) 09101092

Q16. Define physics. (Board 2014) 09101093

Q17. What is meant by zero error and zero correction of vernier callipers? 09101094

Q18. Define metre rule. 09101095

Q19. Define measuring tape. 09101096

Q20. Define vernier callipers. 09101097

Q21. Define screw gauge. Write its Least Count. 09101098

Q22. Define physical balance. 09101099

Q23. Define measuring cylinder. 09101100

Q24. What is meant by international system of units (SI)? 09101101

Q25. Name the telescope which orbits around the Earth? 09101102

Q26. What do you know about digital Vernier calipers? 09101103

Q27. How precision of a balance varies in measuring mass of an object with different balances? 09101104

Q28. Write the laboratory safety rules. 09101105

Q29. How can we round the number? 09101106

Q30: Write the names of the necessary laboratory safety equipment’s. 09101107

Quick Quiz

Q1. Name five prefixes commonly used. 09101108

Q2. Identify the base quantity in the following: 09101109

(i) Speed (ii) Area

(iii) Force (iv) Distance

Q3. Identify the following as base or derived quantity: 09101110

Density, force, mass, speed, time, length, temperature and volume.

Q4. The Sun is one hundred and fifty million kilometers away from the Earth. Write this 09101111

(a) as an ordinary whole number.

(b) In scientific notation.

Q5. Write the number given below in scientific notation. 09101112

(a) 3000000000 ms^-1 (b) 6400000 m

(c) 0.00000000 16g (d) 0.0000548 s

Q6. What is the least count of Vernier calipers? 09101113

Q7. Why do we study Physics? 09101114

Q8. What is the range of vernier callipers used in your physics laboratory? 09101115

Q9. Name any five branches of Physics.

09101116

Q10. How many divisions are there on its veriner scale? 09101117

Q11. Why do we use zero correction? 09101118

Mini Exercise

Q1. What is the least count of a screw gauge? 09101119

Q2. What is the pitch of your laboratory screw gauge? 09101120

Q3. What is the range of your laboratory screw gauge? 09101121

Q4. What is the function of balancing screws in a physical balance? 09101122

Q5. On what pan we place the object and why? 09101123

Q5. How many seconds are in a year?

Ans. 09101124

Q6. Which source gives us pollution free electricity? 09101125

Q7. What is digital vernier calipers? 09101126

Q8. Which one of the two instruments is more precise and why? (Board 2014) 09101127

(a) Vernier Callipers (b) Screw gauge

Solved Examples

Example 1.1

Find the diameter of a cylinder placed between the outer jaws of Vernier Callipers as shown in figure. 09101128

Example 1.2: Find the diameter of a wire using a screw gauge. 09101129

Example 1.3: Find the mass of a small stone by a physical balance. 09101130

Example 1.4: Find the number of significant figures in each of the following values. Also express them in scientific notations. (Board 2014,15) 09101131

(a) 100.8 s (b) 0.00580 km (c) 210.0g

Numerical Problems

Q1.1. Express the following quantities using prefixes. 09101132

(a) 5000 g (b) 2000 000 W

(c) 5210^-10kg (d) 225 10^-8 s

Q1.2 How do the prefixes micro, Nano and pico relate to each other? 09101133

Q1.3 Your hair grows at the rate of 1mm per day. Find their growth rate in nm s^-1.

(Board 2013) 09101134

Q1.4 Rewrite the following in standard form. (Board 2014) 09101135

(a) 116810^-27 (b) 3210⁵

(c) 72510^-5kg (d) 0.0210^-8

Q1.5 Write the following quantities in standard form. 09101136

(a) 6400 km (b) 380 000km

(c) 300, 000, 000ms^-1(d) seconds in a day

Q1.6 On closing the jaws of a Vernier Calipers, zero of the Vernier scale is on the right to its main scale such that 4^th division of its Vernier scale coincides with one of the main scale division. Find its zero error and zero correction. 09101137

Q1.7 A screw gauge has 50 divisions on its circular scale. The pitch of the screw gauge is 0.5mm. What is its least count?

(Board 2013) 09101138

Q1.8 Which of the following quantities have three significant figures? 09101139

(a) 3.0066m (b) 0.00309kg

(c) 5.0510²⁷kg (d) 301.0 s

Q1.9 What are the significant figures in the following measurements? 09101140

(a) 1.009m (b) 0.00450kg

(c) 1.6610²⁷kg (d) 2001 s

Q1.10 A chocolate wrapper is 6.7 cm long and 5.4 cm wide. Calculate its area up to reasonable number of significant figures.

(Board 2014) 09101141

Given data:

Length of chocolate wrapper = 6.7cm.

Width of chocolate wrapper = 5.4cm.

To Find:

Area =?

UNIT 2

KINEMATICS

Q.1 Differentiate between rest and motion. Also give an example that all motions are relative. 09102001

Q.2 What is surrounding? 09102002

Q.3 Explain different types of motion and give examples. Further explain types of translatory motion. (Board 2013) 09102003

Q.4 Differentiate between Scalar and Vector quantities. (Board 2014, 2015) 09102004

Q.5 How is a vector represented? (Board 2013) 09102005

Q.6 What do you know about position? 09102006

Q.7 Differentiate between Distance and Displacement. OR

Describe distance and displacement by diagram and explain. (Board 2014) 09102007

Q.8 Differentiate between Speed and Velocity (Board 2013,14,15) 09102008

Q.9 Define uniform Speed and uniform velocity. (Board 2016) 09102009

Q.10 Define Acceleration and write its formula. (Board 2015) 09102010

Q.11 Define Uniform Acceleration, and give its any example. (Board 2016) 09102011

Q.12 What is meant by positive and negative acceleration? 09102012

Q.13 What is meant by graph? 09102013

Q.14 Explain the Distance-Time Graph. 09102014

Q.15 Explain Speed-time Graph. 09102015

Q.16 How can you calculate distance travelled by a moving object with the help of graph? 09102018

Q.17 What are the equations of motion? 09102019

Q.18 Derive first equation of motion. v_f = v_i + at. with the help of speed-time graph. (OR) Derive the equation of motion which is independent of distance. (Board 2016) 09102020

Q.19: Derive second equation of motion. OR (Board 2013,15,16) 09102021

Derive the equation of motion which is independent of final velocity.

Q.20: Derive third Equation of motion. 2aS = v_f² – v_i²OR(Board 2015)09102022

Derive the equation of motion which is independent of time?

Q.21 How Galileo proved that acceleration of free falling bodies is the same? (Board 2014) 09102023

Q.22 What is gravitational acceleration? Also write its value. (Board 2016) 09102024

Multiple Choice Questions

2.1 Encircle the correct answer from the given choices:

Exercise MCQs

1. A body has translatory motion if it moves along a (Board 2014) 09102025

(a) Straight line (b) circle

2. The motion of a body about an axis is called (Board 2013,14) 09102026

(a) Circular motion (b) rotatory motion

3. Which of the following is a vector quantity? (Board 2016) 09102027

(a) speed (b) distance

4. If an object is moving with constant speed then its distance time graph will be a straight line. 09102028

(a) along time-axis

(b) along distance –axis

(d) inclined to time–axis

5. A straight line parallel to time-axis on a distance-time graph tells that the object is

(a) moving with constant speed 09102029

(b) at rest

(d) in motion

6. The speed–time graph of a car is shown in the figure, which of the following statement is true? 09102030

(a) car has an acceleration of 1.5ms^-2

(b) car has constant speed of 7.5 ms^-1

(d) average speed of the car is 15 ms^-1

7. Which one of the following graphs is representing uniform acceleration?

(Board 2015) 09102031

8. By dividing displacement of a moving body with time, we obtain (Board 2014) 09102032

(a) speed (b) acceleration

9. A ball is thrown vertically upward. Its velocity at the highest point is:

(Board 2013,14) 09102033

(a) -10 ms^-1 (b) zero

10. A train is moving at a speed 36 kmh^-1 Its speed expressed in ms^-109102034

(a) 10 ms^-1 (b) 20 ms^-1

11. A change in position from point A to B is called: (Board 2014) 09102035

(a) speed (b) velocity

12. A car starts from rest. It acquires a speed of 25 ms^-1 after 20 s. The distance moved by the car during this time is 09102036

(a) 31.25 m (b) 250 m

Additional MCQs

13. The fastest bird falcon has speed.

(a) 100kmh^-1 (b) 200 kmh^-1 09102037

14.The average speed of cheetah is: (Board 2014) 09102038

(a) 60kmh^-1 (b) 75kmh^-1

15.The unit of acceleration is : 09102039

(a) ms^-1 (b) ms

16. Displacement is a quantity: 09102040

(a) Scalar (b) Vector

17. The slope of speed time graph is called: 09102041

(a) distance

(b) displacement

(d) acceleration

18. The value of gravitational acceleration when a body is moving in downward direction is: 09102042

(a) 10ms^-1 (b) 10ms^-2

19. The slope of distance time graph shows

(a) speed (b) Displacement

(c). acceleration (d) Distance 09102043

20. The motion of the rider in Ferris wheel is 09102044

(a) Translatory (b) Vibratory

21. First equation of motion is: 09102045

(a) v_f = v_i +at (b) S=

22. If an object is moving with a uniform changing speed then speed time graph is: 09102046

(a) Straight line (b) Variable

23. The unit of velocity and speed is: 09102047

(a) ms (b) ms^-2

24. Brownian motion is an example of: (Board 2014) 09102048

(a) Random motion (b) Linear motion

25. The to and fro motion of a body about its mean position is called: (Board 2014)

(a) Circular motion 09102049

(b) Random motion

(d) Vibratory motion

26. The motion of a body in straight line is :

(Board 2015) 09102050

(a) Random motion

(b) Circular motion

(d) Translatory motion

27. If the velocity of body increases with time, the acceleration will be: 09102051

(a) Negative (b) Uniform

28. If the velocity of body decreases with time then acceleration will be: 09102052

(a) Negative (b) Positive

29. The value of gravitational acceleration for bodies moving upward is: 09102053

(a) 10ms^–1 (b) 10ms^–2

30. Rate of change of velocity is known as:

09102054

(a) Speed (b) Acceleration

31. Pressure is a quantity: 09102055

(a) Scalar (b) Vector

32. Motion of butterfly is an example of:

(a) Random (b) Circular 09102056

33. Graph is plotted between ____ variables:

(a) 2 (b) 3 09102057

34. Independent quantities are taken on:

(a) – x–axis (b) x–axis 09102058

35. Dependent quantities are taken on:

(a) x–axis (b) –ve x–axis 09102059

36. A car covers 100m distance in 10s. Its average speed is: 09102060

(a) 1000 ms^–1 (b) 10 ms^–1

37. A train start from rest. Its velocity becomes 40ms^–1 in 10s. Its acceleration will be: 09102061

(a) 4 ms^–2 (b) 4 ms^–1

38. Paratrooper while coming down attains a velocity called: 09102062

(a) Variable velocity

(b) Terminal velocity

(d) Average velocity

39. LIDAR gun is used to calculate the vehicle’s: 09102063

(a) Velocity (b) Acceleration

40. The acceleration of a body moving with uniform velocity is: 09102064

(a) Zero (b) Variable

41. Relation used to find acceleration is:

09102065

(a) (b)

42. Distance covered by freely falling downward body in first second of motion is:

(a) 5m (b) 29.4m 09102066

43. The quantities that are completely described by only magnitude are: 09102067

(a) Scalar (b) Vector

44. The quantities that describe completely by magnitude and direction are: 09102068

(a) Base (b) Derived

45. The scientist who notice that all the freely falling objects have same acceleration:

(a) Newton (b) Galileo 09102069

46. The velocity of bodies falling down: 09102070

(a) Decreases (b) Increases

47. The velocity of freely falling bodies moving upward: 09102071

(a) Decreases (b) Increases

48. Speedometer measures the: 09102072

(a) Velocity (b) Speed

49. When two bodies are in motion then the velocity of one body relative to the other is called: 09102073

(a) Relative velocity (b) Uniform velocity

50. Quantities between which a graph is plotted are called: 09102074

(a) Scalars (b) Vectors

51. In graph reference point is taken as:

(a) Origin (b) Coordinates 09102075

Exercise Question answers

2.2 Explain translatory motion and give examples of various types of translatory motion. 09102076

2.3 Differentiate between the following: 09102077

i. Rest and motion.

ii. Circular motion and rotatory motion.

iii. Distance and displacement

iv. Speed and velocity.

v. Linear and random motion.

vi. Scalars and vectors.

2.4 Define the terms speed, velocity, and acceleration. 09102078

2.5 Can a body moving at a constant speed have acceleration? 09102079

2.6 How do riders in a Ferris wheel possess translatory motion but not rotatory motion? 09102080

2.7 Sketch a distance-time graph for a body starting from rest. How will you determine the speed of a body from this graph? 09102081

2.8 What would be the shape of a speed – time graph of a body moving with variable speed? 09102082

2.9 Which of the following can be obtained from speed – time graph of a body? 09102083

(i) Initial speed.

(ii) Final speed.

(iii) Distance covered in time t.

(iv) Acceleration of motion.

2.10 How can vector quantities be represented graphically? 09102084

2.11 Why vector quantities cannot be added and subtracted like scalar quantities. 09102085

2.12 How are vector quantities important to us in our daily life? (Board 2016) 09102086

2.13 Derive equations of motion for uniformly accelerated rectilinear motion. 09102087

2.14 Sketch a velocity – time graph for the motion of the body. From the graph explaining each step, calculate total distance covered by the body. 09102088

Additional Short Answer Questions

Q15. How can we write equations of motion under the action of gravity? 09102089

Q16. Write second and third equation of motion in mathematical form.

(Board 2014) 09102090

Q17. Define gravitational acceleration and write its value. (Board 2014) 09102091

Q18. Which is the fastest bird on the Earth? 09102092

Q19. Which is the fastest animal on the Earth? 09102093

Q20. What is LIDAR gun and for what purpose is it used? 09102094

Q21. How does a paratrooper comes to ground? 09102095

Q22. What are the applications of graphs in everyday life? 09102096

Q23. How velocity affects the direction of acceleration? 09102097

Q24. Define average velocity. 09102098

Q25. What does the slope of distance-time graph give? 09102099

Q26. What does the slope of displacement time graph give? 09102100

Q27. What does the slope of velocity time graph give? 09102101

Q28. Define position. 09102102

Q29. Define distance and displacement.

(Board 2016) 09102103

Q30. Define axis. 09102104

Q31. Explain the motion of the Earth about its axis and around the sun. 09102105

Q32. What is meant by deceleration?

09102106

Q33. What is graph? 09102107

Q34. Name the first scientist who noticed freely falling objects? 09102108

Mini Exercise

Q1. When a body is said to be at rest?

09102109

Q2. Give an example of a body that is at rest and in motion at the same time. 09102110

Q3. Mention the type of motion in each of the following: 09102111

i) A ball moving vertically upward Linear motion

ii) A child moving down a slide Linear motion

iii) Movement of a player in a football ground Random motion

iv) The flight of a butterfly Random motion

v) An athlete running in a circular track Circular motion

vi) The motion of a wheel Rotatory motion

vii) The motion of a cradle Vibratory motion

Conversions

Q1. How to convert ms^–1 to kmh^–1? (Board 2016) 09102112

Q2. How to convert kmh^–1 to ms^–1? 09102113

Q3. How to convert ms^–2 to kmh^–2? 09102114

Q4. How convert kmh^–2 to ms^-2? 09102115

Solved Examples

Example 2.1: Represent a force of 80N acting toward North or East. 09102116

Example 2.2

A sprinter completes its 100 metre race in 12s. Find its average speed. 09102117

Example 2.3

A cyclist completes half round of a circular track of radius 318m in 1.5 minutes. Find its speed and velocity. 09102118

Given data:

Radius = r = 318 m

Time taken = t = 1.5 minutes = 1 min. 30S

= 1.5 ´ 60 = 90 sec

Distance covered = p ´ radius

Distance covered = 3.14 ´ 318m = 999m

Displacement = 2 r

Displacement = 2 ´ 318m = 636 m

To Find:

Speed = ?

Velocity = ?

Example 2.4: A car starts from rest. Its velocity becomes 20ms^-1 in 8s. Find its acceleration.

Given Data: 09102119

Initial velocity = v_i = 0 ms^-1

Final velocity = v_f = 20 ms^-1

Time taken = t = 8 s

To Find: a = ?

Example 2.5: Find the retardation produced when a car moving at a velocity of 30ms^-1 slows down uniformly to 15ms^-1 in 5s. (Board 2014) 09102120

Given Data:

Initial velocity = v_i = 30ms^-1

Final velocity = v_f = 15ms^-1

Change in velocity = v_f – v_i

= 15 - 30 = -15 ms^-1

Time taken = t = 5 s

To Find: a = ?

Example 2.6: Figure shows the distance-time graph of a moving car. From the graph, find

(a) The distance car has travelled. 09102121

(b) The speed during the first five seconds.

(c) Average speed of the car.

(d) Speed during the last 5 seconds.

Example 2.7: Find the acceleration from speed-time graph shown in figure 09102122

Example 2.8: Find the acceleration from speed-time graph shown in figure 09102123

Example 2.9

A car moves in a straight line. The speed-time graph of its motion is shown in figure.

From the graph, find 09102124

a. Its acceleration during the first 10 seconds.

b. Its deceleration during the last 2 seconds.

c. Total distance travelled.

d. Average speed of the car during its journey.

Example 2.10:

A car travelling at 10 ms^-1 accelerates uniformly at 2 ms^-2. Calculate its velocity after 5 s.

Given data: (Board 2013) 09102125

v_i = 10 ms^-1

a = 2 ms^-2

t = 5s

To Find:

v_f = ?

Using the first equation

Examples 2.11: A train slows down from 80 kmh^-1 with a uniform retardation of 2 ms^-2. How long will it take to attain a speed of 20kmh^-1? 09102126

Given Data:

v_i = 10 ms^-1

a = 2 ms^-2

t = 5 S

To Find:

v_f = ?

Example 2.12

A bicycle accelerates at 1 ms^-2 from an initial velocity of 4 ms^-1 for 10s. Find the distance moved by it during this interval of time. 09102127

Given Data:

v_i = 4ms^-1

a = 1ms^-2

t = 10s

To Find:

S = ?

Example 2.13

A car travels with a velocity of 5 ms^-1. It then accelerates uniformly and travels a distance of 50 m. If the velocity reached is 15ms^-1. Find the acceleration and the time to travel this distance. 09102128

Given Data:

v_i = 5 ms^-1

s = 50 m

v_f = 15 ms^-1

To Find:

a = ?

t = ?

Solution:

Example 2.14: A stone is dropped from the top of a tower. The stone hits the ground after 5 seconds. Find 09102129

a) The height of the tower.

b) The velocity with which the stone hits the ground.

Given Data:

Initial velocity = v_i = 0

Gravitational acceleration = g = 10 ms^-2

t = 5s

To Find:

S = h = ?

v_f = ?

Example 2.15

A boy throws a ball vertically up. It returns to the ground after 5 seconds. Find 09102130

a. The maximum height reached by the ball.

b. The velocity with which the ball is thrown up.

Given Data:

Gravitational acceleration = g = -10 ms^-2

Time for up and down motion t_o = 5 s

Velocity at maximum height v_f= 0

To Find:

Maximum height = S = h = ?

Initial velocity (upward) = v_i = ?

Numerical Problems

Q. 2.1 A train moves with a uniform velocity of 36 kmh^-1 for 10s. Find the distance travelled by it. 09102131

Given Data:

v = 36 km/h

t = 10 sec

To Find:

S = ?

Q. 2.2 A train starts from rest. It moves through 1 km in 100 s with uniform acceleration. What will be its speed at the end of 100 s. 09102132

Given Data:

= 0

t = 100 sec

S = 1 km = 1000 m

To Find:

= ?

Q.2.3 A car has a velocity of 10 ms^-1. It accelerates at 0.2 ms^-2 for half minute. Find the distance travelled during this time and the final velocity of the car. 09102133

Given Data:

a = 0.2 m/s²

= 10 m/s

t = 0.5 min

= 0.5´60 sec

t = 30 sec

To Find:

S = ?

v_f = ?

Q. 2.4 A tennis ball is hit vertically upward with a velocity of 30ms^-1. It takes 3 s to reach the highest point. Calculate the maximum height reached by the ball. How long it will take to return to ground?

Given Data: 09102134

v_i = 30 ms^-1

t = 3 sec

To Find:

Total time = T = ?

S = ?

= 0

g = -10m/s²

Q. 2.5 A car moves with uniform velocity of 40 ms^-1 for 5 s. It comes to rest in the next 10 s with uniform deceleration. Find (i) deceleration (ii) Total distance travelled by the car. 09102135

Given Data:

v_i = 40 m/s

v_f = 0

t = 10 sec

To Find:

S = ?

a = ?

Q 2.6 A train starts from rest with an acceleration of 0.5 ms^-2. Find its speed in kmh^-1, when it has moved through 100 m.

Given Data: 09102136

v_i = 0

a = 0.5 m/s²

S = 100 m

To Find:

v_f = ?

Q. 2.7 A train staring from rest, accelerates uniformly and attains a velocity 48 kmh^-1 in 2 minutes. It travels at this speed for 5 minutes. Finally, it moves with uniform retardation and is stopped after 3 minutes. Find the total distance travelled by the train.

09102137

V(ms^-1)

Given Data:

= 0

= 48 kmh^-1

From the Speed – Time graph:

AB = V =

OE = 10min =10 ×60 = 600 sec

AC = 5min = 5 × 60 = 300 sec

To Find:

Total distance = S = ?

Q 2.8 A cricket ball is hit vertically upwards and returns to ground 6 s later. Calculate (i) maximum height reached by the ball. (ii) Initial velocity of the ball.

Given Data: 09102138

v_f = 0

g = -10m/s²

Total time = 6 sec Total time = [time to rearch at Max height] + [Time to reach ground]

= 3 +3

= 6 sec

t = 3sec (time to reach maximum height)

To Find:

S = ?

v_i = ?

Q 2.9 When brakes are applied, the speed of a train decreases from 96 kmh^-1 to 48 kmh^-1 in 800 m. How much further will the train move before coming to rest? (Assuming the retardation to be constant).

09102139

Given Data:

S₁ = 800m

v_i = 96 kmh^-1 =

v_f = 48 kmh^-1 =

To Find:

S₂ = ? (Before train stops)

Q. 2.10 In the above problem, find the time taken by the train to stop after the application of brakes. 09102140

Given Data:

v_f = 0 ms^-1

v_i = 26.67 ms^-1

a = -0.333ms^-2

To Find:

t = ?

UNIT 3

DYNAMICS

Q.1 Differentiate between kinematics & dynamics. 09103001

Q.2 Define the following terms: (Board 2014,15) 09103002

(i) Force (ii) Inertia (iii) Momentum

Q.3 State Newton's first law of motion. Why is it called law of inertia? (Board 2014-16) 09103003

Q.4 State and Derive Newton's Second law of motion. (Board 2013) 09103004

Q.5 Define Newton (unit of force) or Define force and write the name of its unit? (Board 2016) 09103005

Q. 6 What is the difference between Mass & weight?

or Give two differences between Mass & Weight. (Board 2014,15) 09103006

Q.7: Explain Newton’s Third Law of Motion. 09103007

Q.8 Define tension. Also write its conditions during the vertical motion of a block. 09103008

Q.9: Find the tension and acceleration during vertical motion of two bodies attached to the ends of a string that passes over a frictionless pulley. (Board 2013) 09103009

Q10. What is Atwood machine? 09103010

Q.11: Find out a relation for acceleration and tension for motion of two bodies attached to the ends of a string that passes over a frictionless pulley such that one body moves vertically and the other moves on a smooth horizontal surface. 09103011

Q.12: Show that rate of change of momentum is equal to applied force. (OR) (Board 2015)

How can you relate a force with the change of momentum of a body? 09103012

Q.13 Explain law of conservation of momentum? Also drive its formula.

or State and explain law of conservation of momentum. (Board 2014) 09103013

Q.14 Define friction and how does it produce? 09103014

Q.15 Define Limiting friction. 09103015

Q.16 What is meant by coefficient of friction? Write its mathematical form. (Board 2014) 09103016

Q.17 Why is rolling friction less than sliding friction? (Board 2014) 09103017

Q.18 Write a few applications of rolling friction. 09103018

Q.19: How does Braking and Skidding happen? 09103019

Q.20 Write advantages and disadvantages of friction. 09103020

Q.21 Write down a few methods of reducing friction. 09103021

Q.22 Define circular motion. Also write its example. 09103022

Q.23 Define and explain centripetal force and write down its mathematical form.

Q.24 Define centrifugal force. (Board 2014) 09103024

Q.25 From where does centripetal force F_c come during motion on circular (curved) track? 09103025

Q.26 Why is the outer edge of road kept higher than inner edge? (Board 2013) 09103026

OR What is meant by banking of road?

Q.27 Explain the working of washing machine. (OR) How does washing machine dryer work? 09103027

MULTIPLE CHOICE QUESTIONS

3.1 Encircle the correct answer from the given choices

Exercise MCQs

1. Newton’s first law of motion is valid only in the absence of: (Board 2014) 09103029

(a) force (b) net force

2. Inertia depends upon: (Board 2014,16) (a) force (b) net force 09103030

3. A boy jumps out of a moving bus. There is a danger for him to fall: 09103031

(a) towards the moving bus

(b) away from the bus

(d) opposite to the direction of motion

4. A string is stretched by two equal and opposite force 10 N each. The tension in the string is: (Board 2013) 09103032

(a) zero (b) 5N

5. The mass of a body: 09103033

(a) decreases when accelerated

(b) increases when accelerated

(d) none of the above.

6. Two bodies of masses m₁ and m₂ attached to the ends of an inextensible string passing over a frictionless pulling such that both move vertically. The acceleration of the bodies is: 09103034

(a) (b)

7. Which of the following is the unit of momentum? (Board 2014) 09103035

(a) Nm (b) kgms^-2

8. When horse pulls a cart, the action is on the: (Board 2014) 09103036

(a) cart (b) Earth

9. Which of the following material lowers friction when pushed between metal plates? (a) water (Board 2014,15) 09103037

(b) fine marble powder

Additional MCQs

10. The study of motion without reference to mass and force: 09103038

(a) Mechanics (b) Dynamics

11. Which is unitless quantity: 09103039

(a) mass (b) force

12. The direction of momentum is:

(a) opposite to motion 09103040

(b) along the velocity

(d) None

13. Which law of motion is called law of inertia: 09103041

(a) first law of motion

(b) second law of motion

(d) law of conservation of momentum

14. The unit of momentum is: (Board 2015)

(a) kgms^-2 (b) kgms^-109103042

15. Action and reaction are always on:

(a) same body 09103043

(b) different bodies

(d) None

16. Mass is measured by: 09103044

(a) spring balance

(b) measuring cylinder

(d) None

17. Weight is measured by: 09103045

(a) spring balance

(b) measuring cylinder

18. Formula of weight is derived from which law? 09103046

(a) first law (b) second law

(d) Law of conservation of momentum

19. Walking on earth is the example of which law? 09103047

(a) first law (b) second law

(d) Law of momentum

20. Motion of a rocket is the example of which law? 09103048

(a) first law (b) second law

(d) law of momentum

21. If the weight of body is greater then tension then body will. 09103049

(a) move upward

(b) move downward

(d) None

22. If a force of 25 N is acting along the string to balance the weight then tension in string is. 09103050

(a) 25 N (b) 50 N

23. The rate of change of momentum is equal. (Board 2016) 09103051

(a) mass (b) force

24. If no external force acting on a body then such system is called. 09103052

(a) ideal system

(b) controlled system

(d) None

25. The force which opposes the motion is called. 09103053

(a) momentum (b) friction

26. Which type of friction is minimum?

(a) sliding (b) limiting 09103054

27. Which type of friction is maximum? (a) Sliding (b) Rolling 09103055

28. Friction is due to 09103056

(a) Roughness (b) Shape

29. When a block is place on the surface its weight produce 09103057

(a) tension (b) momentum

30. What is the effect of lubrication?

(a) increase friction 09103058

(b) No effect

(d) None

31. In circular motion, the motion of every particle of body is 09103059

(a) different (b) opposite

32. The force which compels a body to move in circle is: 09103060

(a) centripetal force

(b) centrifugal force

(d) tension

33. If the velocity of a moving body in a circle is doubled, then its centripetal force is (a) double (b) half 09103061

34. The centripetal acceleration is always are along 09103062

(a) Normal forces

(b) Centripetal forces

(d) horizontal force

35. The unit of coefficient of friction (a) Newton (b) ms^-1 09103063

36. Coefficient of friction between tyre and dry road is. (Board 2014) 09103064

(a) 0.6 (b) 1

37. 1 Newton = _______ (Board 2014) 09103065

(a) 1kg ms^-2 (b) 1 kg ms

38. The weight of boy is 147N. Its mass will be _________ when g = 10ms^-2 09103066

(a) 1.47 kg (b) 14.7 kg (Board 2014)

39. Product of mass and velocity of a body is called: (Board 2013) 09103067

(a) Torque (b) Force

40. In isolated system the momentum after collision of two bodies. (Board 2015) 09103068

(a) increase (b) constant

41. If radius of circle is doubled then centripetal acceleration becomes: 09103069

(a) Doubled (b) Three times

42. Rolling friction is ________ then sliding friction: 09103070

(a) Greater (b) Less

43. If the mass of moving body in a circle is doubled then centripetal force will be: 09103071

(a) Doubled (b) Half

44. Momentum is a quantity. 09103072

(a) Scalar (b) Vector

45. Which machine is used to find acceleration due to gravity? 09103073

(a) Centrifuge

(b) Atwood machine

(d) Washing machine

46. Co-efficient of friction between glass and glass. 09103074

(a) 1.0 (b) 0.9

47. Co-efficient of friction between wood and concrete. 09103075

(a) 0.62 (b) 0.8

48. Laws of motion was presented by the Scientist. 09103076

(a) Einstein (b) Newton

49. If the mass of body is doubled while keeping the force constant, then acceleration will be: 09103077

(a) Doubled (b) One Half

50. When a force of 4 Newton is applied on a body of mass 2kg, the acceleration produced in it will be: 09103078

(a) 2ms^-2 (b) 4ms^-2

51. The weight of body on earth with mass 8kg is: 09103079

(a) 10 N (b) 100 N

52. Which parameter remain same everywhere? 09103080

(a) Force (b) Mass

53. If a 20 N weight of block change with the string vertically then tension in string is: 09103081

(a) 0 N (b) 20 N

54. The maximum value of friction is: 09103082

(a) Kinetic friction

(b) Static friction

(d) Dynamic friction

55. Sliding friction can be changed into rolling friction by using: 09103083

(a) Ball bearing (b) Roller bearing

56. The velocity and acceleration of body moving with uniform speed in a circular path will be: 09103084

(a) In same direction

(b) In opposite direction

(d) Equal

57. The weight of a body if 20Kg is: 09103085

(a) 2 N (b) 10 N

58. F = _________ 09103086

(a) P_f – P_i (b) P_i – P_f

59. Kgms^-2 is equal to: 09103087

(a) Joule (b) Mole

60. Walking on earth is the example of 09103088

(a) 1^st law of motion

(b) Second law of motion

(d) Law of conservation of energies

Short Answer Questions

Q.3.2 Define the following terms. 09103089

(i) Inertia (ii) Momentum (iii) Force

(iv) Force of friction (v) Centripetal force

Q.3.3 What is the difference between?

(i) Mass and weight 09103090

(ii) Action and reaction

(iii) Sliding friction and rolling friction

Q.3.4 What is the law of inertia? 09103091

Q.3.5 Why is it dangerous to travel on the roof of a bus? 09103092

Q.3.6 Why does a passenger move outward when a bus takes a turn? 09103093

Q.3.7 How can you relate a force with the change of momentum of a body? 09103094

Q.3.8 What will be the tension in a rope that is pulled from its ends by two opposite forces 100 N each? 09103095

Q.3.9 Action and reaction are always equal and opposite. Then how does a body move?

09103096

Q.3.10 A horse pushes the cart. If the action and reaction are equal and opposite then how does the cart move? 09103097

Q.3.11 What is the law of conservation of momentum? 09103098

Q.3.12 Why is the law of conservation of momentum important? 09103099

Q.3.13 When a gun is fired, it recoils, why?

09103100

Q.3.14 Describe two situations in which force of friction is needed. 09103101

Q3.15 How does oiling the moving parts of a machine lower friction? 09103102

Q3.16 Describe ways to reduce friction.

(Board 2013,14) 09103103

Q3.17 Why rolling friction is less than sliding friction? (Board 2013) 09103104

Q3.18 What you know about the following.

Q3.19. What would happen if all friction suddenly disappears? 09103106

Q3.20. Why the spinner of a washing machine is made to spin at a very high speed? 09103107

Q3.21. Define centripetal force. Write its equation. (Board 2016) 09103108

Additional Short Questions

Q.22 What is perforated wall? 09103109

Q.23 What is meant by an inextensible string? 09103110

Q.24 Why the riders of coaster cars do not fall out of it? 09103111

Q.25 Which force is highly desirable when climbing up a hill? 09103112

Q.26 Write two real life application of friction. 09103113

Q.27 Why the shape of fast moving vehicles must be streamlined? 09103114

Q.28 What is the direction of centripetal force and its components? 09103115

Q.29 Define momentum. 09103116

Q.30 For a body of mass "m" moving in a circle of radius "r". If its velocity is doubled, what will be the effect on value of centripetal force? 09103117

Q.31 What is cold welds? 09103118

Q.32 How a person enable himself to move up in between the opposite walls with the help of his hands and feet? 09103119

Q.33 If we tied a stone at the end of a string and start moving it in circular motion, name the forces acting on the stone and the string. 09103120

Q.34 What is an isolated system? 09103121

Q.35 On which principle rockets and jet engines works? And How? 09103122

Q.36 Why fragile objects are packed with Styrofoam rings or polythene sheets?

09103123

Q.37 What happened when a person is not wearing seat belts had an accident? 09103124

Q.38 How seatbelts of a car are useful?

Q.39 What happened when a vehicle had an accident at high speed? What safety precautions offered by the car? 09103126

Q.40 What is Centrifuge? What is its function? 09103127

Q.41 Why it is hard to stop a fast moving and heavy vehicles? 09103128

Quick Quiz

Q1. Stretch out your palm and hold a book on:

i. How much force you need to prevent the book from falling? 09103129

ii. What is action? 09103130

iii. Is there any reaction? If yes, then what is its direction? 09103131

Q2. Which shoes offer less friction? 09103132

i. Which shoe is better for walking on dry track? 09103133

ii. Which shoes is better for jogging?

09103134

iii. Which sole will wear out early? 09103135

iv. Why is it easy to role cylindrical eraser on a paper sheet than to slide it? 09103136

Q4. Do we roll or slide the eraser to remove the pencil work from our note book? 09103178

Mini Exercise

Q.1 (1) In which case do you need smaller force and why? 09103138

(i) rolling (ii) sliding

2. In which case it is easy for the tyre to roll over? 09103139

(i) rough ground (ii) Smooth ground

SOLVED EXAMPLES

Example 3.1

Find the acceleration that is produced by a 20 N force in a mass of 8 kg. 09103140

Example 3.2: A force acting on a body of mass 5 kg produces an acceleration of 10ms^-2. What acceleration the same force will produce in a body of mass 8 kg. 09103141

Example 3.3

A cyclist of mass 40 kg exerts a force of 200 N to move his bicycle with an acceleration of 3ms^-2. How much is the force of friction between the road and the tyres. 09103142

Example 3.4: Two masses 5.2 kg and 4.8 kg are attached to the ends of an inextensible string which passes over a frictionless pulley. Find the acceleration in the system and the tension in the string when both the masses are moving vertically. 09103143

Example 3.5: Two masses 4 kg and 6 kg are attached to the ends of an inextensible string which passes over a frictionless pulley such that mass 6 kg is moving over a frictionless horizontal surface and the mass 4 kg is moving vertically downwards. Find the acceleration in the system and the tension in the string. 09103144

EXAMPLE 3.6: A body of mass 5 kg is moving with velocity of 10ms^-1. Find the force required to stop it in 2 seconds. 09103145

EXAMPLE 3.7: A bullet of mass 20 g is fired from a gun with a muzzle velocity 100 ms^-1. Find the recoil of the gun if its mass is 5 kg. 09103146

Example 3.8

A stone of mass 100 g is attached to a string 1 m long. The stone is rotating in a circle with a speed of 5ms^-1. Find the tension in the string. 09103147

NUMERICAL PROBLEMS

3.1 A force of 20 N moves a body with an acceleration of 2ms^-2.What is its mass?

Given data (Board 2013) 09103148

Force = F = 20N

Acceleration = a = 2ms^-2

To find:

Mass = m = ?

3.2 The weight of a body is 147 N. What is its mass? (Take the value of g as 10ms^-2)

Given data (Board 2013,15) 09103149

Weight = w = 147N

g = 10 ms^-2

To find:

Mass = m = ?

3.3 How much force is needed to prevent a body of mass 10 kg from falling? 09103150

Given data

Mass = m = 10kg

g = 10ms^-2

To find:

Force = F = ?

This force acts in upward direction.

3.4 Find the acceleration produced by a force of 100 N in a mass of 50 kg. 09103151

Given data (Board 2014)

Force = F = 100N

mass = m = 50kg

To find:

Acceleration = a = ?

3.5 A body has weight 20 N. How much force is required to move it vertically upwards with an acceleration of 2ms^-2?

Given data 09103152

Weight = W = F₁= 20N

Acceleration a = 2ms^-2

g = 10 ms^-2

To find:

Force = F = ?

3.6 Two masses 52 kg and 48 kg are attached to the ends of string that passes over a frictionless pulley. Find the tension in the string and acceleration in the bodies. When both the masses are moving vertically. 09103153

Given data

m₁ = 52 kg

m₂ = 48 kg

g = 10 ms^-2

To find:

T = ?

a = ?

3.7 Two masses 26 kg and 24 kg are attached to the ends of a string which passes over a frictionless pulley. 26 kg is lying over a smooth horizontal table. 24 N mass is moving vertically downward. Find the tension in the string and the acceleration in the bodies. 09103154

Given data

m₁ = 24 kg

m₂ = 26 kg

g = 10 ms^-2

To find:

T = ?

a = ?

3.8 How much time is required to change 22 Ns momentum by a force of 20 N? Given data (Board 2014) 09103155

DP = 22Ns

F = 20N

To find:

t = ?

3.9 How much is the force of friction between a wood block of mass 5 kg and the horizontal marble floor? The coefficient of friction between wood and marble is 0.6?

Given data (Board 2016) 09103156

Mass = m = 5 kg

Coefficient of friction m = 0.6

To find:

Friction = F_s =?

3.10 How much centripetal force is needed to make a body of mass 0.5 kg to move in a circle of radius 50 cm with a speed 3 ms^-1?

Given data 09103157

Mass = m = 0.5 kg

Radius r = 50cm

= 0.5m

velocity = v = 3 ms^-1

To find:

Centripetal force = F_c= ?

UNIT 4

TURNING EFFECT OF FORCES

Q1. Define parallel forces. Also explain its types. (OR) What is the difference between like and unlike parallel forces? (Board 2014) 09104001

Q2. What is meant by addition of forces? 09104002

Q3. What is meant by resolution of forces? Explain. (OR) Define rectangular components? How can a force be resolved into its rectangles component? (Board 2016) 09104003

Q4. How can we determine a force from its perpendicular components? Also find its direction. 09104004

Q5. What is meant by rigid body and axis of rotation? 09104005

(OR) What is the difference between rigid body and axis of rotation? (Board 2014)

Q6. What is meant by torque or moment of a force? Explain the factors on which it depends.

Q7. Define line of action of force and moment arm. (Board 2013,16) 09104007

Q8.What is meant by principle of moments? Explain clockwise moment and anticlockwise moment. or What is moment? Write its principle. (Board 2014) 09104008

Q9. What is meant by centre of mass? (Board 2015) 09104009

Q10. What is meant by Centre of Gravity?

or Define centre of gravity (Board 2013,14,16) 09104010

Q11. Define plumb line. 09104011

Q12. Describe an experiment which explains the centre of gravity of an irregular shaped thin lamina. or How can you find centre of gravity of irregular shaped body? Explain it with experiment. (Board 2014,16) 09104012

Q13. Define couple and couple arm. Explain the process of couple. (Board 2013) 09104013

(OR) Define Couple. How torque produced in right body due to couple? (Board 2016)

Q14. Define equilibrium also explain the first condition of equilibrium and second condition of equilibrium. 09104014

Q15. Explain states of equilibrium. 09104015

Q16. Explain with example the stability and position of centre of mass. 09104016

MULTIPLE CHOICE QUESTIONS

Exercise MCQs

1. Two equal but unlike parallel forces having different lines of action produce:

(a) a torque 09104017

(b) a couple

(d) neutral equilibrium

2. The number of forces that can be added by head to tail rule are:

(Board 2015) 09104018

(a) 2 (b) 3

3. The number of perpendicular components of a force are:

(Board 2013,14,16) 09104019

(a) 1 (b) 2 (c) 3 (d) 4

4. A force of 10 N is making an angle of 30^o with the horizontal. Its horizontal component will be: (Board 2013,16) 09104020

(a) 4 N (b) 5 N

5. A couple is formed by: 09104021

(a) two forces perpendicular to each

other

(b) two like parallel forces

(d) two equal and opposite forces

not in the same line

6. A body is in equilibrium when its: (a) acceleration is uniform 09104022

(b) speed is uniform

(d) acceleration is zero.

7. A body is in neutral equilibrium when its centre of gravity: 09104023

(a) is at its highest position

(b)is at the lowest position

(d) is situated at its bottom

8. Racing cars are made stable by:

(Board 2014) 09104024

(a) increasing their speed

(b) decreasing their mass

(d) decreasing their width

Additional MCQs

9. The parallel forces which have same direction are called: 09104025

(a) resultant force

(b) like parallel forces

(d) Null forces

10. The vector which has the same effect as the combined effect of vectors: 09104026

(a) negative vector

(b) the vector

(d) Zero vector

11. is called: 09104027

(a) sin q (b) cos q

12. Tan q is equal to: 09104028

(a)

(b)

(c)

(d)

13. is called: 09104029

(a) cos q (b) sin q

14. Sin 45^o is 09104030

(a) 0.707 (b) 0.5

15. Cos 0⁰ is 09104031

(a) 0 (b) 2

16. To find x component of force ‘F’ we use formula: 09104032

(a) F cos q (b) F sin q

17. The formula of y component of force ‘F’ is: 09104033

(a) F cos q (b) F sin q

18. The formula to find resultant force ‘F is: 09104034

(a) (b)

19. The unit of torque is: 09104035

(a) Nm^-2 (b) Ncm

20. The conditions of equilibrium are:

(a) 2 (b) 3 09104036

21. The centre of gravity of uniform triangle is: 09104037

(a) Point of intersection of its medians

(b) on its vertex

(d) point of intersection of diagonal

22. The centre of gravity of hollow cylinder is the middle point on its: 09104038

(a) curved side (b) axis

23. Forces on double arm spanner are called: 09104039

(a) Torque (b) couple

24. After tilting if body come back to its original position then the body is in:

(a) stable equilibrium 09104040

(b) unstable equilibrium

(d) equilibrium

25. Turning effect of a force is called: (Board 2014) 09104041

(a) torque (b) moment

26. First condition of equilibrium is:

(a) (Board 2014) 09104042

(b)

(c)

(d) All of these

27. Complete equation = 09104043 (a) (b) (Board 2014)

28. It is easy to turn a steering wheel by applying a : 09104044

(a) torque (b) force

29. The value of tan 45^o is: 09104045

(a) 0.5 (b) 1.732 (Board 2014)

30. If and , what is the magnitude of resolution of force: 09104046 (a) 7N (b) 5N (Board 2014)

31. The net torque acting on a rotating body with uniform speed is: 09104047

(a) 1 (b) 2 (Board 2014,15) (c) 5 (d) 0

32. In right angle triangle, length of base is 4cm and its hypotenuse is 5cm, then length of perpendicular is: (Board 2013,14) 09104048

(a) 1 cm (b) 20 cm

33. The centre of gravity of irregular shaped body can be found with the help of :

(Board 2013) 09104049

(a) wedge (b) meter rod

34. At what angle sinq and cosq has same values: 09104050

(a) 30° (b) 45°

35. If we increase the length of spanner, the torque produced will be: 09104051

(a) increased (b) decreased

36. Unit of Resultant force is: 09104052

(a) Nm^-2 (b) N.m

37. Center of gravity of a uniform square is:

09104053

(a) Intersection of diagonals

(b) Point of intersection of medians

(d) None of these

38. Centre of gravity of sphere is at:

(Board 2014) 09104054

(a) centre of sphere

(b) outside of sphere

(d) none of these

Exercise Question Answer

Q 4.2. Define the following: 09104055

(i) Resultant vector

(ii) Torque

(iii) Centre of mass

(iv) Centre of gravity

Q 4.3. Differentiate the following: 09104056

(i) Like and unlike forces

(ii) Torque and couple

(iii) Stable and neutral equilibrium

Q 4.4. How head to tail rule helps to find the resultant of forces? 09104057

Q 4.5. How can a force be resolved into its rectangular components? 09104058

Q 4.6. When a body is said to be in equilibrium? (Board 2016) 09104059

Q 4.7. Explain the first condition for equilibrium. 09104060

Q 4.8. Why there is a need of second condition for equilibrium if a body satisfies first condition for equilibrium? 09104061

Q 4.9. What is second condition for equilibrium. Write its formula. (Board 2016) 09104062

Q 4.10. Give an example of a moving body which is in equilibrium. 09104063

Q 4.11. Think of a body which is at rest but not in equilibrium. (Board 2016) 09104064

Q 4.12. Why a body cannot be in equilibrium due to single force acting on it? 09104065

Q 4.13. Why the height of vehicles is kept as low as possible? 09104066

Q 4.14. Explain what is meant by stable, unstable and neutral equilibrium. Give one examples in each case. 09104067

Additional Short Questions

Q.15 How many forces can be added by head to tail rule? 09104068

Q.16 Why is door easy to open or close by pushing or pulling at handle? 09104069

Q.17 How is wheel of bicycle rotated? 09104070

Q.18 Why there is a need of second condition for equilibrium if a body satisfies first condition for equilibrium? 09104071

Q.19 Why is a vehicle made heavy at its bottom to keep its centre of gravity as low as possible? (Board 2013) 09104072

Q.20 Define perpendicular components.

(Board 2014) 09104073

Q.21 Define resolution of force. Write the names of its components. (Board 2014) 09104074

Q.22 On doubling the moment arm, find its effect on the value of torque. 09104075

Q.23 Define Trigonometry. 09104076

Q.24 Define Trigonometric Ratios. 09104077

Q.25 A force "F" is acting on a body at an angle with x-axis. Write the magnitude of horizontal and vertical component. 09104078

Q.26 Define component of forces. 09104079

Q.27 Define rigid body. 09104080

Q.28 Define axis of rotation. 09104081

Q.29 Define moment arm. 09104082

Q.30 Define clockwise and anti clockwise moments. 09104083

Q.31 State the principle of moment. 09104084

Q.32 Define plumb line. 09104085

Q.33 How direction of torque can be found? 09104086

Q.34 Why the handle of a door is fixed near the outer edge of a door? (OR) Why it is easy to open and close the door by pulling (or) pushing it at its handle? 09104087

Q.35 Is the paratrooper coming down in the state of equilibrium. 09104088

Q.36 Why we use a spanner instead of hand to loosen a bike axle nut? 09104089

Q.37 How women and children in the villages carry water pitchers on their heads? 09104090

Q.38 Which type of forces are required to start a bus? 09104091

Q.39 Give an example of a body when the resultant force is zero but resultant torque is not zero. 09104092

Quick Quiz

Q1. Can a small child play with a fat child on the see-saw? Explain how? 09104093

Q2. Two children are sitting on the see-saw, such that they cannot swing. What is the net torque in this situation? 09104094

Q3. A ladder leaning at a wall as shown in figure is in equilibrium. How? 09104095

Q4. The weight of the ladder in fig. produces an anti-clock wise torque. The wall pushes the ladder at its top end thus produces a clock wise torque. Does the ladder satisfy second condition of equilibrium? 09104096

Q5. Does the speed of a ceiling fan go on increasing all the time? 09104097

Q6. Does the fan satisfy second condition of equilibrium when rotating with uniform speed? 09104098

Mini Exercise 1

In a right angled triangle length of base is 4 cm and its perpendicular is 3 cm. Find: (Board 2014)

(i) Length of hypotenuse 09104099

(ii) Sin q (iii) Cos q (iv) Tan q

Mini Exercise 2

A force of 150 N can loosen a nut when applied at the end of a spanner 10 cm long. 09104100

(i) What should be the length of the spanner to loosen the same nut with a 60 N Force

(ii) How much force would be sufficient to loosen it with a 6 cm long spanner?

SOLVED EXAMPLES

EXAMPLE 4.1: Find the resultant of three forces 12 N along x-axis, 8 N making an angle of 45^owith x-axis and 8 N along y-axis. 09104101

EXAMPLE 4.2

A man is pulling a trolley on a horizontal road with force of 200 N making 30⁰withthe road. Find the horizontal and vertical components of its force.

Given Data: (Board 2015) 09104102

F = 200 N

q = 30^oWith the horizontal

To Find:

F_x= ?

F_y = ?

EXAMPLE 4.3: A mechanic tightens the nut of a bicycle using a 15 cm long spanner by exerting a force of 200 N. Find the torque that has tightened it. (Board 2013) 09104103

Given Data:

To Find:

F = 200 N

L = 15 cm = 0.15 m

Examples 4.4: A metre rod is supported at its middle point O as shown in figure. The block of weight 10 N is suspended at point B, 40 cm from O. Find the weight of the block that balances it at point A, 25 cm from O. 09104104

Given Data:

W₂ = 10N

Moment arm of W₁ = OA = 25cm = 0.25m

Moment arm of W₂ = OB = 40cm = 0.40m

To Find:

W₁ = ?

Example 4.5: A block of weight 10 N is hanging through cord as shown in figure. Find the tension in the cord. 09104105

Given Data:

Weight of the block w = 10N

To Find:

Tension in the cord T = ?

Example 4.6

A uniform rod of length 1.5 m is placed over a wedge at 0.5 m from its one end. A force of 100 N is applied at one of its ends near the wedge to keep it horizontal. Find the weight of the rod and the reaction of the wedge. 09104106

Given Data:

F = 100 N

OA = 0.5 m

AG = BG = 0.75 m

OG = AG – AO = 0.75 m -0.5 m

= 0.25 m

To Find:

w = ?

R = ?

NUMERICAL PROBLEMS

4.1. Find the resultant of the following forces. 09104107

Given data

1) 10 N along x – axis

2) 6 N along y axis

3) 4 N along x-aixs

From Triangle OAD

Net force

Along x – axis = Fx = 10 – 4 = 6 N

F_x = 6N

Net force acting

Along y – axis

F_y = 6N

To find:

F = ?

4.2 Find the perpendicular components of a force of 50 N making an angle of 30^o with x-axis. 09104108

Given data

Force = F = 50 N

Angle = Q = 30^o with x axis

To find:

Y component = F_y = ?

X component = F_x = ?

4.3 Find the magnitude and direction of a force, if its x-component is 12N and y-component is 5N. 09104109

Given data:

X component = F_x = 12 N

Y component = F_y = 5N

To find:

Resultant force = F = ?

Direction = =?

Direction of resultant = force = F = ?

4.4. A force of 100 N is applied perpendicularly on a spanner at a distance of 10 cm from a nut. Find the torque produced by the force. 09104110

Given data:

Force = F = 100N

Moment arm = L = 10cm

To find:

Torque = t = ?

4.5 A force is acting on a body making an angle of 30^o with the horizontal. The horizontal component of the force is 20 N. Find the force. (Board 2014) 09104111

Given data

Horizontal component of force = F_x = 20N

Angle = q = 30^o

To find:

Force = F = ?

4.6. The steering of a car has a radius 16 cm. Find the torque produced by a couple of 50 N. (Board2013,14,15) 09104112

Given data:

Radius = r = 16 cm

= = 0.16 m

Force = F = 50 N

To find:

Torque due to couple = t = ?

4.7 A picture frame is hanging by two vertical strings. The tensions in the strings are 3.8 N and 4.4 N. Find the weight of the picture frame. 09104113

Given Data:

Tension in 1st string = T₁= 3.8 N

Tension in 2nd string = T₂= 4.4N

To find:

Weight of picture frame = w = ?

4.8 Two blocks of masses 5 kg and 3 kg are suspended by the two strings as shown. Find the tension in each string.

Given data: 09104114

Mass of 1^st block = m₁ = 5 kg

Weight of 1^st block

= w₁= m₁g = 5 ´ 10

= 50N

Mass of 2^nd block = m₂ = 3 kg

Weight of 2^nd block = w₂ = m₂g

= 3 ´ 10

= 30 N

To find:

Tension in 1^st string = T₁ = ?

Tension in 2^nd string = T₂ = ?

4.9 A nut has been tightened by a force of 200 N using 10 cm long spanner. What length of a spanner is required to loosen the same nut with 150 N force? 09104115

Given data:

Force = F = 200N

Moment arm = L₁ = 10 cm

L₁ =

To find:

Torque = t = ?

Length of spanner = Moment arm = L₂ = ?

If F = 150N

4.10 A block of mass 10 kg is suspended at a distance of 20 cm from the centre of a uniform bar 1 m long. What force is required to balance it at its centre of gravity by applying the force at the other end of the bar? 09104116

Given data:

Mass of block = m = 10 kg

Weight of block = w = 10 ´ 10

W = 100 N

Distance of weight from C.G. = AG = 20 cm

AG = = 0.2 m

Distance of force from C.G. BG = 50 cm

To find:

Force on the other end to balance the rod = W₂ = ?

UNIT 5

GRAVITATION

Q1. Who is the first man who gave the idea of gravity? 09105001

Q2. What is meant by the force of gravitation? Also explain the law of gravitation.

Q3. Why can we not feel the force of attraction between the objects around us? 09105003

Q4. How does Law of Gravitation relate with third Law of Motion? 09105004

Q5. How can you say that gravitational force is a field force? 09105005

Q6. What is gravitational field strength near the surface of the Earth? (Board 2014) 09105006

Q7. Find the mass of Earth by using the law of gravitation. (Board 2014,15) 09105007

Q8. How the value of ‘g’ varies with altitude? 09105008

Q9. Explain the artificial satellites? 09105009

Q10. Define satellites. Find the orbital velocity of on artificial satellites. (Board 13,14,15)

Or Describe the method to find orbital speed of artificial satellites? 09105010

MULTIPLE CHOICE QUESTIONS

Exercise MCQs

1. Earth’s gravitational force of attraction vanishes at: (Board 2014,16) 09105011

(a) 6400km (b) infinity

2. Value of g increases with the: 09105012

(a) increase in mass of the body

(b) increase in altitude

(d) none of the above

3. The value of g at a height one Earth’s radius above the surface of the Earth is:

(a) 2 g (b) 09105013

4. The value of g on moon’s surface is 1.6 ms^-2. What will be the weight of a 100 kg body on the surface of the moon?

(Board 2013) 09105014

(a) 100 N (b) 160 N

5. The altitude of geostationary orbits in which communication satellites are launched above the surface of the Earth is: 09105015

(a) 850 km (b) 1000 km

6. The orbital speed of a low orbit satellite is: 09105016

(a) zero (b) 8 ms^-1

Additional MCQs

7. The first man who gave the idea of gravity: 09105017

(a) Hero (b) Einstein

8. Earth revolves around the: 09105018

(a) Moon (b) Sun

9. Law of Gravitation is consistence with:

(a) 1^st Law of motion 09105019

(b) 2^nd Law of motion

(d) Law of momentum

10. Gravitational force is a: 09105020

(a) Electric force

(b) Magnetic force

(d) electromotive force

11. Near the Earth surface, the gravitational field strength is:

(Board 2013) 09105021

(a) 1N kg^-1 (b) 100 Nkg^-1

12. Mass of Earth is equal to: 09105022

(a) 7.1 ´ 10²⁴kg (b) 6.0 ´ 10²⁴kg

13. The value of ‘g’ on the surface of moon is: (Board 2014-15-16) 09105023

(a) 1.62 ms^-2 (b) 10ms^-2

14. The value of ‘g’ on the surface of Mars: 09105024

(a) 3.73 ms^-2 (b) 1.62 ms^-2

15. The value of ‘g’ is greater at: 09105025

(a) moon (b) Hills

16. The velocity of geostationary satellites with respect to the Earth is 09105026

(a) maximum (b) Zero

17. Moon is our satellite: 09105027

(a) artificial (b) permanent

18. GPS system consist of earth satellites: 09105028

(a) 4 (b) 24

19. Orbital velocity v_o =: 09105029

(a) (b)

20. Moon is nearly km away from the Earth: (Board 2014) 09105030

(a) 3,80,000km (b) 3800 km

21. A satellite revolving around very close to Earth has speed nearly: 09105031

(a) 5 kms^-1 (b) 8 kms^-1

22. The Earth attracts a body with a force equal to its: 09105032

(a) velocity (b) gravity

23. The value of gravitational constant “G” is Nm²kg^-2: 09105033

(a) 6.67 ´ 10^-21 (b) 6.67 ´ 10^-11

24. The unit of gravitational constant is: (Board 2016) 09105034

(a) Nm²kg (b) Nm²kg^-2

25. Moon completes its one revolution around earth in days: 09105035

(a) 22 (b) 23 (Board 2014)

26. The relationship between gravitation acceleration and the radius of the earth is: 09105036

(a) (b)

27. Earth completes one rotation about its axis in: 09105037

(a) 27 days (b) 364 days

28. Weight of the body is due to the: 09105038

(a) gravitation force

(b) centripetal force

(d) All of the above

29. Velocity of the body moving in upward direction from the centre of the earth.

(a) Increases 09105039

(b) decreases

(d) None

30. Weight of the body is_______to the gravity force between body and earth:

(a) Less than (b) greater than 09105040

31. Weight of the body when we increase its height from earth's surface: 09105041

(a) Increases (b) Decreases

32. Speed of the satellites of GPS around earth is: 09105042

(a) 3.87 ms^-1 (b) 387 Kms^-1

33. The radius R of the earth is: 09105043

(a) (b)

34. At the surface of the earth value of 'g' is measured by using formula: 09105044

(a) (b)

35. The value of g is maximum at: 09105045

(a) Mountains

(b) Maximum height

(d) At 2R

Exercise Question Answers

Q.5.2 What is meant by force of gravitation?

(Board 2015,16) 09105046

Q.5.3 Do you attract the Earth or Earth attracts you? Which one is attracting with a larger force? You or the Earth. 09105047

Q.5.4 What is a field force? 09105048

Q.5.5 Why could earlier scientists not guess about the gravitational force? 09105049

Q.5.6 How can you say that gravitational force is a field force? 09105050

Q.5.7 Explain, what is meant by gravitational field strength?(Board 13-15)09105051

Q.5.8 Why is law of Gravitation important to us? 09105052

Q.5.9 Explain the law of gravitation. 09105053

Q.5.10 How the mass of Earth can be determined? 09105054

Q.5.11 Can you determine the mass of our moon? If yes, then what do you need to know? 09105055

Q.5.12 Why does the value of “g” vary from place to place? 09105056

Q.5.13 Explain how the value of “g” varies with altitude? 09105057

Q.5.14 What are artificial satellites? (Board 2013) 09105058

Q.5.15 How Newton’s law of gravitation helps in understanding the motion of satellites? 09105059

Q.5.16 On what factor the orbital speed of a satellite depends? (Board 2016) 09105060

Q.5.17 Why communication satellites stationed at geostationary orbits?

(Board 2014) 09105061

Additional Short Questions

Q.13 What is GPS? or What is navigation system? (Board 2014) 09105062

Q.14 Does the weight of an apple increase, decrease or remain constant when taken to the top of a mountains? 09105063

Q15. What is satellite? What are their kinds? 09105064

Q.16 What is the height and speed of geostationary satellites from the surface of the Earth? (Board 2014) 09105065

Q.17 Why are communication satellites geostationary satellite? 09105066

Q.18 How far Moon is from Earth and in how much time it complete its rotation?

09105067

Q.20 Write equation of gravitational acceleration at height h from the surface of Earth according to Newton's law of gravitation. 09105068

Q.21 Write the equation from which we can calculate the mass of Earth?

(Board 2013) 09105069

Q.22 How the gravitational force attraction would be affected if the distance between 2 bodies is doubled? 09105070

Q.23 At what height value of 'g' would become one-ninth than on the surface of the earth? 09105071

Q.24 Why all the planets and the earth move around/revolve around the sun? 09105072

Q.25 Define gravitational field? 09105073

Q.26 What is the effect of mass on gravitational acceleration? 09105074

Ans. Since

Q.27 What is the effect of distance of freely falling bodies from the centre of the earth? 09105075

Q.28 Does there any difference between the values of ‘g’ at the equator and at the poles? 09105076

Q.29 When a man is standing on the ground, how much upward force is exerted on him by the earth? Why does not this force lift him from the earth upward? 09105077

Q.30 What is orbital speed of a low orbit satellite? (Board 2016) 09105078

MINI EXERCISE

Q.1 Does an apple attract the Earth towards it? 09105079

Q.2 With what force an apple weighing 1N attracts the Earth? 09105080

Q.3 Does the weight of an apple increase, decrease or remain constant when taken to the top of a mountain? 09105081

SOLVE EXAMPLES

Example 5.1;

Two lead spheres each of mass 1000 kg are kept with their centers 1 m apart. Find the gravitational force with which they attract each other. 09105082

Given data

Here m₁ = 1000 kg

m₂ = 1000 kg

d = 1m

G = 6.673 10^-11 Nm² kg^-2

To Find: F = ?

Example 5.2

Calculate the value of g, the acceleration due to gravity at an altitude 1000km. The mass of the Earth is 6.0 x 10²⁴ kg. The radius of the Earth is 6400km. 09105083

Given data:

Here R = 6400 km

h = 1000 km

M_e = 6.0 ´ 10²⁴ kg

To find:

g_h = ?

R + h = 6400 km + 1000 km

= 7400 km = 7400 x 10³m

= 7.4 x 10⁶ m

NUMERICAL PROBLEMS

5.1. Find the gravitational force of attraction between two spheres each of mass 1000 kg. The distance between the centers of the spheres is 0.5 m. 09105084

Given Data

Mass of first sphere = m₁ = 1000 kg

Mass of second sphere= m₂= 1000 kg

The distance between their centers =d= 0.5m

Gravitational constant =

G = 6.673 ´ 10^-11Nm² kg^-2

To find:

Gravitational force = F =?

5.2. The gravitational force between two identical lead spheres kept at 1 m apart is 0.006673 N. Find their masses. 09105085

Given data

Gravitational force = F = 0.006673 N

Distance between two identical spheres

d = 1m

Gravitational Constant =

G = 6.673 10^-11 Nm² kg^-2

To find:

Masses of identical sphere m₁ =m₂ = m=?

5.3. Find the acceleration due to gravity on the surface of the Mars. The mass of Mars is 6.42 ´ 10²³kg and its radius is 3370 km. 09105086

Given data

Mass of Mars = M = 6.410²³ kg

Radius of Mars = R = 3370 km

R = 3370 10³m Gravitational constant =

G = 6.6710^-11 Nm²kg^-2

To find:

Gravitational acceleration = g = ?

5.4. The acceleration due to gravity on the surface of moon is 1.62 ms^-2. The radius of Moon is 1740 km. Find the mass of moon.

Given Data 09105087

Acceleration due to gravity on the surface of moon = g_m = 1.62 ms^-2

The radius of Moon

R_m = 1740 km = 1740 x 10³ m

Gravitational constant

G = 6.673 ´ 10^-11 Nm²kg^-2

To find:

Mass of Moon =M_m = ?

5.5. Calculate the value of g at a height of 3600 km above the surface of the Earth.

Given data: 09105088

Height = h = 3600 km

h = 3600 ´ 10³m Þ 3600000m

R = 6.4 ´ 10⁶m

G = 6.673 ´ 10^-11 Nm²kg^-2

M = 6 ´ 10²⁴kg

To find:

gh = ?

5.6. Find the value of g due to the Earth at geostationary satellite. The radius of the geostationary orbit is 48700 km. 09105089

Given Data:

Radius of the geostationary orbit

R = 48700 km

R = 48700 ´ 10³m

G = 6.673 ´ 10^-11 Nm²kg^-2

Mass of Earth = M = 6 ´ 10²⁴ kg

To find:

g = ?

5.7. The value of g is 4.0 ms^-2 at a distance of 10000 km from the centre of the Earth. Find the mass of the Earth. 09105090

Given Data:

g = 4ms^-2

Height= h = 10000km

h = 10000 ´ 10³m

h = 10⁷m

G = 6.673 ´ 10^-11Nm² kg^-2

To find:

Mass of Earth = M_e = ?

5.8. At what altitude the value of g would become one fourth than on the surface of the earth? 09105091

Given Data

g_h =

To Find altitude h = ?

5.9. A polar satellite is launched at 850 km above Earth. Find its orbital speed.

Given Data: (Board 2014) 09105092

R = 6.4 ´10⁶m

Height = h = 850 km

h = 850 ´ 10³m

G = 6.673 ´ 10^-11 Nm²kg^-2

Me = 6 ´ 10²⁴ kg

To find:

V_orb= ?

5.10. A communication satellite is launched at 42000 km above Earth. Find its orbital speed. 09105093

Given data

h = 42000km

h = 42000 ´ 10³m

Mass of earth = M_e = 6 ´10²⁴kg

G = 6.673 ´ 10^-11 Nm² kg^-2

To find:

V_orb = ?

UNIT 6

WORK AND ENERGY

Q.1 Define work. Write its condition, formula and unit. (Board 2013-15) 09106001

Q.2 What is the unit of work, define it? (Board 2014) 09106002

Q3. Define Energy. Write the names of its forms. 09106003

Q4. Define kinetic energy. Derive its formula K.E = mv². Write its examples. 09106004

or Define kinetic energy and also write its equation. (Board 2014-15)

Q5. Define potential energy. Give its examples and derive its equation P.E =m g h. 09106005

or Define potential energy and write its formula. (Board 2014)

Q6. Explain the different forms of energy. 09106006

Q7. Explain interconversion of energy. OR How is energy converted from one form to another? Explain. 09106007

Q8. What are the major sources of energy? Explain. 09106008

Q9. Write a note on Solar House Heating System. (Board 2014) 09106009

Q10. Write the uses of Wind Energy. (Board 2014) 09106010

Q11. What is the geothermal energy? 09106011

Q12. How energy is obtained from biomass? 09106012

Q13. What is mass-energy equation? Explain. (Board 2013) 09106013

Q14. How does electricity produce from fossil fuels? 09106014

Q15. How does the use of energy in different ways pollute our environment? (OR) What are the environmental issues associated with energy? 09106015

Q16. What methods should be adopted to control the pollution? 09106016

Q17. Explain flow diagram of an energy converter. 09106017

Q18. Define efficiency. Write its formula. OR What is meant by the efficiency of a system?

(Board 2014) 09106018

Q19. Define power and write its formula. (Board 2014-15) 09106019

Q20. What is the SI unit of power? Define it. OR Define the unit of power “Watt”?

(Board 2014, 16) 09106020

MULTIPLE CHOICE QUESTIONS

6.1 Encircle the correct answer from the given choices:

Exercise MCQs

1. The work done will be zero when the angle between the force and the distance is: (Board 2013-14) 09106021

(a) 45^o (b) 60^o

2. If the direction of motion of the force is perpendicular to the direction of motion of the body, then work done will be:

(a) Maximum (b) Minimum 09106022

3. If the velocity of a body becomes double, then its kinetic energy will:

(a) Remain the same 09106023

(b) Become double

(d) Become half

4. The work done in lifting a brick of mass 2 kg through a height of 5m above ground will be: (Board 2014) 09106024

(a) 2.5 J (b) 10 J

5. The kinetic energy of a body of mass 2 kg is 25 J. Its speed is: 09106025

(a) 5ms^-1 (b) 12.5 ms^-1

6. Which one of the following converts light energy into electrical energy?

(a) Electric bulb (Board 2014) 09106026

(b) Electric generator

(d) Electric cell

7. When a body is lifted through a height h, the work done on it appears in the form of its: 09106027

(a) Kinetic energy

(b) Potential energy

(d) Geothermal energy

8. The energy stored in coal is 09106028

(a) Heat energy

(b) Kinetic energy

(d) nuclear energy

9. The energy stored in a dam is: 09106029

(a) Electric energy (Board 2014)

(b) Potential energy

(d) Thermal energy

10. In Einstein’s mass-energy equation, c is the: 09106030

(a) Speed of sound (b) Speed of light

Additional MCQs

11. Rate of doing work is called: (Board 2016) 09106031

(a) Energy (b) Torque

12. In Einstein’s mass-energy equation, c means speed of light. Its value is:

09106032

(a) 3´10^-8 ms^-1 (b) 3´10⁸ ms^-1

13. A body possesses if it is capable to do work: 09106033

(a) Energy (b) Power

14. If a person is not moving when he lifts a load on his head work is. 09106034

(a) FS (b) FS cosq

15. Formula of work is: 09106035

(a) F x S (b) F x v

16. 1MJ =

(a) 10³ J (b) 10⁶ J

17. Running water possess energy: 09106036

(a) Kinetic

(b) potential

(d) Gravitational potential Energy

18. The energy of a body during the motion is called: 09106037

(a) Potential Energy (b) Kinetic Energy

19. Formula of Gravitational potential Energy is: 09106038

(a) mgh (b)

20. Stretched bow has type of energy:

(a) Kinetic energy (Board 2013) 09106039

(b) mgh

(d) Elastic potential energy

21. One horse power is equal to: 09106040

(a) 746 w (b) 749 w

22. Which quantity is scalar? 09106041

(a) Force (b) Power

23. Solar cells are also known as:

(a) Electric cell (b) Photo cells 09106042

24. A solar cell is made up of wafers of:

(a) Silicon (b) Aluminum

25. How many components are there of a solar heating system? 09106044

(a) 2 (b) 3

26. Kinetic and potential energy are the kinds of energy: 09106045

(a) Chemical (b) Nuclear

27. From following, which one is a renewable source of energy? 09106046

(a) Coal (b) Gas

28. Mass-energy equation was given by:

(a) Newton (b) Einstein 09106047

29. A temperature rise in the environment disturbs life is called: 09106048

(a) Air pollution

(b) Land pollution

(d) Thermal pollution

30. What kind of waste is produced by nuclear power plant? 09106049

(a) Carbon dioxide (b) radio active

31. An ideal system gives output: 09106050

(a) 50% (b) 70%

32. Fossil fuels are usually: 09106051

(a) Carbon dioxide

(b) Hydrogen

(d) Carbon monoxide

33. Einstein’s mass-energy equation relation is: 09106052

(a) E = (b) E = mc²

34. The energy present in our food is:

(a) Mechanical energy 09106053

(b) Gravitational potential energy

(d) Nuclear energy

35. Which of following units is equal to Kgm²s^-2. 09106054

(a) Newton (b) Joule

Exercise Question Answers

Q.6.2 Define work. What is its SI unit? 09106055

Q.6.3 When does a force do work? Explain. 09106056

Q.6.4 Why do we need energy? 09106057

Q.6.5 Define energy, give two types of mechanical energy. 09106058

Q.6.6 Define K.E. and derive its relation. 09106059

Q.6.7 Define potential energy and derive its relation. 09106060

Q.6.8 Why fossil fuels are called non-renewable sources of energy? 09106061

Q.6.9 Which form of energy is most preferred and why? 09106062

Q.6.10 How is energy converted from one form to another? Explain. 09106063

Q.6.11 Name the five devices that convert electrical energy into mechanical energy.

09106064

Q.6.12 Name a device that converts mechanical energy into electrical energy. (Board 2014) 09106065

Q.6.13 What is meant by the efficiency of a system? 09106066

Q.6.14 How can you find the efficiency of a system? 09106067

Q.6.15 What is meant by the term power? 09106068

Q.6.16 Define watt. 09106069

Additional Short Question Answers

Q.1 How a pole vaulter acquired changes of energy? 09106070

Q.2 How mechanical energy changes into heat energy? (Board 2013-14) 09106071

Q3. Differentiate between sound energy and mechanical energy? (Board 2014) 09106072

Q4. How can every citizen be helpful in controlling air pollution? (Board 2014) 09106073

Q5. Write two disadvantages of thermal pollution. 09106074

Q6. Why geothermal wells are made? (Board 2014) 09106075

Q7. How our body gets energy? 09106076

Q8. How a nuclear power plant get energy? 09106077

Q9. Why is it not possible to make a 100% efficient system? 09106078

Q10. Write down the equation of Einstein and value of c. (Board 2014) 09106079

Q11. What is an ideal system? 09106080

Q.12. What are the bigger units of power?

09106081

Q13. How much Sun’s energy reaches the Earth? 09106082

Q14. Name some uses of solar cells? 09106083

Q15.What are the uses of solar panel?09106084

Q16. What are the components of solar heating system? Name them. 09106085

Q17. What are the types of mechanical energy? 09106086

Q18. Which kind of energy possessed by stored water and a raised hammer? 09106087

Q19. Which energy is possessed by a stretched bow? 09106088

Q22. How clouds are formed? 09106089

Q.23 Which energy changes are the reason of soil erosion? 09106090

Q19. What kind of energy possess by running water? 09106091

Q20. What will be the kinetic energy of the body if its velocity is double? 09106092

Q24. What is the other name of solar cells?

09106093

Q25. In E = mc², what does ‘c’ represent?

09106094

Q26. What is meant by interconversion of energy? 09106095

Q.27. What is biomass? 09106096

Q.28. Which power plants produce the most heat? 09106097

Q.29. What is meant by nuclear fission reaction? 09106098

Q.30. Differentiate between renewable and non-renewable energy sources. 09106099

Q.31. Differentiate between solar cells and solar panels. 09106100

Q.32. Which harmful waste is produced by burning fossil fuels? 09106101

Q.33. What health problems created due to burning of fossil fuels? 09106102

Q.34. Differentiate between chemical and mechanical energy? (Board 2016) 09106103

Mini Exercise

Q.1: A crate is moved by pulling the rope attached to it. It moves 10 m on a straight horizontal road by a force of 100 N. How much work will be done if

i. The rope is parallel to the road.

ii. The rope is making an angle of 30^o with the road. 09106104

Given Data:

Distance = S = 10m

Force = F = 100N

To Find:

Work = W = ?

Q.2: The Kinetic energy of a body of mass 2kg is 25 J. Find its speed.

(Board 2014) 09106105

Given Data:

To Find:

Q.3: A machine does 4 joule of work in 2 sec, calculate its power. 09106106

Given data

Work = W = 4 joule

time = t = 2 sec

To Find:

Power = ?

SOLVED EXAMPLES

Example 6.1

A girl carries a 10 kg bag upstairs to a height of 18 steps, each 20 cm high. Calculate the amount of work she has done to carry the bag. (Take g = 10ms^-2) 09106107

Given Data:

Mass of the bag m = 10kg

Weight of the bag w = mg

= 10 kg ´ 10 ms^-2

= 100 N

To Find:

Work = W = ?

Example 6.2

A stone of mass 500g strikes the ground with a velocity of 20ms^-1. How much is the kinetic energy of the stone at the time it strikes the ground? (Board 2013-14) 09106108

Given Data:

m = 500g = 0.5kg

v = 20ms^-1

To Find:

K.E = ?

Example 6.3:-

A body of mass 50kg is raised to a height of 3m. What is its potential energy? 09106109

(g = 10ms^-2)

Given Data:

Mass = m = 50 kg

Height= h = 3 m

g = 10 ms^-2

To Find:

P.E. = ?

Example 6.4

A force of 200 N acts on a body of mass 20 kg. The force accelerates the body from rest until it attains a velocity of 50 ms^-1. Through what distance the force acts? 09106110

Given Data:

Force = F = 200N

Mass = m = 20 kg

Velocity = v = 50 ms^-1

To Find:

Distance = S = ?

Example 6.5

A cyclist does 12 joules of useful work while pedaling his bike from every 100 joules of food energy which he takes. What is his efficiency? 09106111

Example 6.6

A man M₁ takes 80 s in lifting a load of 200 N through a height of 10 m. While another man M₂ takes 10 s in doing the same job. Find the power of each. 09106112

Given data:

F = 200 N

S = 10 m

Time taken by man M₁ = t₁ = 80s

Time taken by man M₂ = t₂ = 10s

To Find:

Power = ?

Example 6.7

Calculate the power of a pump which can lift 70 kg of water through a vertical height of 16 meters in 10 seconds. Also find the power in horse power. 09106113

Given Data:

Mass of water = m = 70 kg

Height = S = 16 m

Time taken = t = 10 s

To Find:

Power = ?

NUMERICAL PROBLEMS

6.1 A Man has pulled a cart through 35m applying a force of 300N. Find the work done by the man. 09106114

Given data

Force = F = 300 N

Distance = S = 35 m

Work = W = ?

6.2 A block weighing 20N is lifted 6 m vertically upward. Calculate the potential energy stored in it. 09106115

Given data:

Force = F = W = mg = 20 N

Height = h = 6m

To find:

Potential Energy = E = ?

6.3 A car weighing 12 kN has speed of 20 ms^-1. Find its kinetic energy. 09106116

Given data: (Board 2015)

Weight = W = mg = 12 kN

mg = 12 10³N

m10 = 1210³

m = kg

m = 1210² kg.

v = 20 ms^-1.

To find: K.E = ?

6.4 A 500 g stone is thrown up with a velocity of 15ms^-1. Find its,

(i) P.E at maximum height

(ii) K.E when it hits the ground 09106117

Given data:

mass = 500g 0. 5 kg.

Initial velocity = V_i = 15 ms^-1

Final velocity = V_f= 0

To Find:

P.E = ?

K.E = ?

6.5 On reaching the top of a slope 6m high from its bottom, a cyclist has a speed of 1.5 ms^-1. Find the kinetic energy and the potential energy of the cyclist. The mass of the cyclist and his bicycle is 40kg. 09106118

Given Data:

Height of Inclined

Plane = h = 6m

Initial speed = v_i = 1.5 ms^-1.

To Find:

K.E = ?

P.E. = ?

6.6 A motor boat moves at a steady speed of 4ms^-1. Water resistance acting on it is 4000 N. Calculate the power of its engine.

Given Data: 09106119

Speed of Motor Boat = v = 4ms^-1

force = F = 4000 N

To Find:

Power = P = ?

6.7 A man pulls a block with a force of 300 N through 50 m in 60 s. Find the power used by him to pull the block.

(Board 2015) 09106120

Given Data:

Force = F = 300 N

Time = t = 60 s

Height = h = 50 m

To Find:

Power = P = ?

6.8. A 50kg man moved 25 steps up in 20 seconds. Find his power, if each step is 16 cm high. (Board 2014) 09106121

Given data

Mass = m = 50 kg

Time = t = 20 sec.

No of steps = 25

Height of each step = h = 16cm

To Find:

Power = ?

6.9 Calculate the power of a pump which can lift 200 kg of water through a height of 6 m in 10 seconds. 09106122

Given Data: (Board 2013-14)

mass = m = 200 kg

time = t = 10 sec

height = h = 6m

To Find:

Power = P = ?

6.10 An electric motor of 1 hp is used to run water pump. The water pump takes 10 minutes to fill an overhead tank. The tank has a capacity of 800 liters and height of 15 m. Find the actual work done by the electric motor to fill the tank. Also find the efficiency of the system. 09106123

Given Data:

(Density of water = 1000 kgm^-3)

(Mass of 1 liter of water = 1kg)

Power of motor = 1 hp

= 746 watt.

Time = t = 10 min

= 10 60 sec

= 600 sec.

Height = h = 15m

Capacity of tank = v = 800 liter.

To Find:

Work = W = ?

Efficiency = ?

UNIT 7

PROPERTIES OF MATTER

Q1. Describe briefly about the matter? 09107001

Q2. What are the features of kinetic molecular model of matter? (Board 2013-14,16) 09107002

Q3. Explain states of matter. (Board 2013) 09107003

Q.4. Define Plasma. Discuss it as fourth state of matter. (Board 2014) 09107004

Q.5. Define density and write down its mathematical form and unit. (Board 2013) 09107005

Q.6. Calculate the density of 5 liter of water having mass 5 Kg. 09107006

Q7. Define pressure and write its formula. (Board 2014-15) 09107007

Q8. What is atmospheric pressure? Explain it with the help of experiment. (OR) Show by experiment that atmospheric pressure exert in all direction. 09107008

Q. 9 How can we measure the atmospheric pressure? or Explain the method to measure the atmospheric pressure. 09107009

Q10. Explain the variation in atmospheric pressure. (OR) How atmospheric pressure vary with height. 09107010

Q.11 What do you mean by pressure of liquids? Also prove that P= rgh. 09107011

Q12. State the Pascal’s law. What are its applications in our daily life? (Board 2013-15) 09107012

Q13. Explain the working of Hydraulic press. (OR) Find force applied on large piston using Pascal's law in hydraulic press. 09107013

Q14. Explain braking system in vehicles which work on the principle of Pascal’s law. 09107014

Q15. State and explain Archimedes principle. How can we determine the density of solid using it? 09107015

Q16. Under what conditions an object sinks and floats on the surface of water? 09107016

Q17. What is the principle of floatation? 09107017

Q18. Write the Applications of Archimedes principle. 09107018

Q19. Define elasticity. (Board 2016) 09107019

Q20. Define stress and write its formula and unit. 09107020

Q21. Define and Explain Strain. 09107021

Q22. State and explain Hooke’s Law. or Define Hooke's law and elastic limit. 09107022

Q23. What do you mean by Young’s modulus? Derive formula to calculate young's modulus.

09107023

MULTIPLE CHOICE QUESTIONS

7.1 Encircle the correct answer form the given choices:

Exercise MCQs

1. In which of the following state molecules do not leave their position? (Board 2016)

(Board 2015) 09107024

(a) Solid (b) liquid

2. Which of the substance is the lightest one? (Board 2016) 09107025

(a) copper (b) mercury

3. SI unit of pressure is pascal, which is equal to: (Board 2013) 09107026

(a) 10⁴Nm^-2 (b) 1 Nm ^-2

4. What should be the approximate length of a glass tube to construct a water barometer? (Board 2014) 09107027

(a) 0.5 m (b) 1 m

5. According to Archimedes, up thrust is equal to: 09107028

(a) weight of displaced liquid

(b) volume of displaced liquid

(d) none of these

6. The density of a substance can be found with the help of : 09107029

(a) Pascal’s law

(b) Hooke’s law

(d) Principle of floatation

7. According to Hooke’s law: 09107030

(a) Stress strain = constant

(b) Stress / strain = constant

(d) Stress = strain

The following force-extension graphs of a spring are drawn on the same scale. Answer the questions given below from (viii) to (x).

8. Which graph does not obey Hooke’s law as shown in above _____ 09107031

(a) (b)

9. Which graph gives the smallest value of spring constant? 09107032

(a) (b)

10. Which graph gives the largest value of spring constant? 09107033

(a) (b)

Additional MCQs

11. Substances having specific shape and volume are called. 09107034

(a) solids (b) liquids

12. Such state of matter which has no specific shape is called. 09107035

(a) solid (b) liquid, gas

13. Most of the matter that fills the universe is in state: 09107036

(a) solid (b) plasma

14. 1litre is equal to: 09107037

(a) 10² m³ (b) 10^-3m³

15. The formula of Density is:

(a) (b) 09107038

16. Pressure is quantity: 09107039

(a) Scalar (b) Vector

17. The formula of pressure is:

(a) F x a (b) 09107040

18. The density of water is: 09107041

(a) 5500 kgm^–3 (b) 10000 kgm^–3

19. The Fourth state of matter is 09107042

(a) Solid (b) Liquid

20. As we go up the value of atmospheric pressure is: 09107043

(a) Decreased (b) Increased

21. At sea level, the atmospheric pressure is about 09107044

(a) 101320 Pa (b) 101300 Pa

22. Atmospheric pressure is measured by an instrument called. 09107045

(a) Barometer (b) Altimeter

23. How many times Mercury is denser than water? 09107046

(a) 12.5 (b) 13.6

24. During the hot summer day the value of atmospheric pressure is: 09107047

(a) Increases (b) Decreases

25. Which of following works on Pascal's law? (Board 2014) 09107048

(a) Screw gauge (b) Vernier callipers

26. In SI system, unit of density is:

(Board 2013) 09107049

(a) kgm^-1 (b) kgm^-3

27. Hydraulic press is a machine which works on: 09107050

(a) Hook’s law (b) Pascal’s law

28. Density is quantity: 09107051

(a) Scalar (b) Vector

29. Highly conducting state of matter is:

(a) Solid (b) Liquid 09107052

30. As we go up the density of air in the atmosphere: 09107053

(a) decreases (b) increases

31. At a height of 30km, atmospheric pressure is: 09107054

(a) 101300Pa (b) 1000 Pa

32. Where there is no air the atmospheric pressure is: 09107055

(a) Zero (b) 101300P_a

33. Minor but rapid change in atmospheric pressure causes: 09107056

(a) Poor condition (b) Intense condition

34. Decrease in atmospheric pressure predicts: 09107057

(a) Rainy condition (b) Intense condition

35. An increasing with decline in atmospheric pressure cause: 09107058

(a) Rainy condition (b) Pleasant condition

36. A gradual large increase in atmospheric pressure shows: 09107059

(a) Pleasant condition (b) Rainy condition

37. Which property can be determine by Archimedes principle: 09107060

(a) Vapour pressure (b) Density

38. The type of hydrometer which is used to measure the concentration of acid in a battery is called: 09107061

(a) Chemical meter (b) Acid meter

39. Formula for finding the density of an object is: 09107062

(a) (b)

40. Which of the substance is heaviest?

(a) Copper (b) Mercury 09107063

41. Atmospheric pressure acts in: 09107064

(a) Upward direction (b) Downward direction

42. Liquid pressure at depth h is: 09107065

(a) r/gh (b) h/rg

43. Archimedes is a scientist: 09107066

(a) Greek (b) Italian

44. Unit of strain is: 09107067

(a) Nm^-2 (b) Nm

45. Tensile strain produces the change in the object: 09107068

(a) length (b) Volume

46. Young’s Modulus = 09107069

(a) AD/FL_o (b) FL_o/ADL

Exercise Question Answers

Q.7.2 How kinetic molecular model of matter is helpful in differentiating various states of matter? 09107070

Q.7.3 Does there exist a fourth state of matter? What is that? 09107071

Q.7.4. What is meant by density? What is its SI unit? 09107072

Q.7.5 Can we use a hydrometer to measure the density of milk? (Board 2014) 09107073

Q.7.6. Define the term pressure. (Board 2016)

09107074

Q.7.7. Show that atmosphere exerts pressure. (Board 2016) 09107075

Q.7.8 It is easy to fill air in a balloon but it is very difficult to remove air from a glass bottle. Why? 09107076

Q.7.9 What is a barometer? 09107077

Q.7.10 Why water is not suitable to be used in a barometer? (Board 2014) 09107078

Q.7. 11 What makes a sucker pressed on a smooth wall sticks to it? 09107079

Q.7.12 Why does the atmospheric pressure vary with height? 09107080

Q.7.13 What does it mean when the atmospheric pressure at a place fall suddenly? 09107081

Q.7.14 What changes are expected in weather if the barometer reading shows a sudden increase? 09107082

Q.7.15 State Pascal’s law. 09107083

Q.7.16 Explain the working of hydraulic press. 09107084

Q.7.17 What is meant by elasticity? 09107085

Q.7.18 State Archimedes principle. 09107086

Q.19 What is upthrust? Explain the principle of floatation. 09107087

Q.7.20 Explain how a submarine moves up the water surface and down into water.

09107088

Q.7.21 Why does a piece of stone sink in water but a ship with a huge weight floats?

(Board 2014-15) 09107089

Q.7.22 What is Hooke’s Law? What is meant by elastic limit? 09107090

Ans. See Q. No. 22.

Q.7.23 Take a rubber band. Construct a balance of your own using a rubber band. Check its accuracy by weighing various objects. 09107091

ADDITIONAL ANSWER QUESTIONS

Q.1 What is effect on atmospheric pressure as we go higher? 09107092

Q.2 How vacuum cleaner works? 09107093

Q.3 How liquid push up in straw? 09107094

Q.4 How liquid enter in the syringe?

09107095

Q.5 What is hydrometer? 09107096

Q.6 What is deforming force? 09107097

Q.7 What changes has to be done for making a water barometer? 09107098

Q.8 Is atmospheric pressure at mounta-ins higher or lower than at sea level? 09107099

Q.9 What is the atmospheric pressure at a height about 30km? 09107100

Q.10 What will be atmospheric pressure at attitude where there is no air? 09107101

Q.11 What changes in a weather expected if there is a minor but rapid fall in atmospheric pressure? 09107102

Q.12 What does decrease in atmospheric pressure predict? 09107103

Q.13 What does an increase in atmospheric pressure predict? 09107104

Q.14 What does a gradual large increase in the atmospheric pressure indicates? 09107105

Q.15 Which physical property can be determine by Archimedes principle? 09107106

Q.16 What is the atmospheric pressure at sea level? 09107107

Q.17 On what factors pressure of a liquid depends? 09107108

Q.18 What is the fourth state of matter? 09107109

Q.19 State Pascal’ law. 091071110

Q.20 State the Archimedes principle.

(Board 2016) 09107111

Q.21 State the principle of floatation. 09107112

Q.22 Define elasticity and elastic body. 09107113

Q.23 Define stress and strain.

(Board 2016) 09107114

Q.24 Define elastic limit, Hooke’s Law and Young’s modulus. 09107115

Q.25 Why iron is heavier than wood? 09107116

Q.26 Why the shape of soap bubbles is spherical? 09107117

Q.27 How soap bubbles are formed? 09107118

Q.28 Why a large log of wood floats on water but a steel needle sinks? 09107119

Q.29 Explain the conditions when objects float or sink in water? 09107120

SOLVED EXAMPLES

EXAMPLE 7.1 (Board 2013-14-15) 09107121

The mass of 200 cm³of stone is 500 g. Find its density.

Given data:

m = 500g

v = 200 cm³

To Find:

Density = ?

EXAMPLE 7.2

In a hydraulic press, a force of 100 N is applied on the piston of a pump of cross-sectional area 0.01m². Find the force that compresses a cotton bale placed on larger piston of cross- sectional area 1 m² 09107122

Given Data:

Here F₁ = 100N

a = 0.01 m²

A = 1 m²

To Find:

F₂ = ?

EXAMPLE 7.3

A wooden cube of sides 10 cm each has been dipped completely in water. Calculate the upthrust of water acting on it 09107123

Given Data:

Length of side L = 10 cm = 0.1m

Volume V = L³=(0.1m)³ = 110^-3 m³

Density of water = 1000 kgm^-3

To Find:

Upthrust = ?

EXAMPLE 7.4

The weight of a metal spoon in air is 0.48 N. Its weight in water is 0.42 N. Find its density. 09107124

Given Data:

Weight of the spoon w₁= 0.48 N

Weight of spoon in water w₂ = 0.42 N

To Find:

Density = ?

Solution:

EXAMPLE 7.5

An empty meteorological balloon weighs 80 N. It is filled with 10cubic metres of hydrogen. How much maximum contents the balloon can lift besides its own weight? The density of hydrogen is 0.09kgm ^-3and the density of air is 1.3kgm^-3. 09107125

Given Data:

Weight of the balloon w = 80 N

Volume of hydrogen V = 10m³

Density of hydrogen = 1.3 kg m^-3

Density of air ₁= 0.09 kg m^-3

To Find:

Weight of hydrogen w₁= ?

Weight of the contents w₂= ?

EXAMPLE 7.6

A barge, 40 metre long and 8 metre broad, whose sides are vertical, floats partially, loaded in water. If 125000 N of cargo is added, how many meters will it sink? (Board 2013) 09107126

Given Data:

Area of the barge A = 40 8

= 320 m²

Additional load w to carry W = 125000 N

To find:

Depth = h = ?

EXAMPLE 7.7

A steel wire 1 m long and cross- sectional area 510^-5m²is stretched through 1 mm by a force of 10,000 N. Find the Young’s modulus of the wire. 09107127

Given Data:

Force F = 10,000 N

Length L_o= 1m

Extension L = 1mm = 0.001m

Cross sectional Area A = 510^-5m²

To Find:

Y = ?

NUMERICAL PROBLEMS

7.1 A wooden block measuring 40 cm10cm5cm has a mass 850 g. Find the density of wood? 09107128

Given data

Volume = 40 cm 10 cm 5cm

= 2000 cm³

= 2000 (10^-2)³

= 2000 10^-6m³

= 210^-3m³

Mass = m = 850 g =

= 0.85 kg

To Find:

Density = d = ?

7.2 How much would be the volume of ice formed by freezing 1 litre of water? (Board 2014) 09107129

Given Data:

Volume of water = V_w= 1 Litre = 1 10^-3m³Since 1 litre = 10^-3m³

Density of water = r_w= 1000 kg m^-3

Density of ice = d_ice = 920 kgm^-3

To Find:

Volume of ice = V_ice = ?

7.3 Calculate the volume of the following objects: 09107130

(i) An iron sphere of mass 5 kg, the density of iron is 8200 kgm^-3

(ii) 200 g of lead shot having density 113000 kgm^-3

(iii) A gold bar of mass 0.2 kg the density of gold is 19300 kgm^-3(Board 2015)

Given Data:

(i) Mass = m = 5 kg

Density = d = 8200 kgm^-3

To Find:

Volume = V = ?

(ii)

Given data:

mass = m = 200g = kg = 0.2 kg

Density = d = 11300 kg m^-3

To find:

Volume = V = ?

(iii)

Given data

mass = m = 0.2 kg

Density = d = 193000 kgm^-3

To find:

Volume = V = ?

7.4 The density of air is 1.3 kgm^-3Find the mass of air in a room measuring 8 m 5 m 4 m. (Board 2013-14) 09107131

Given Data

Density = = 1.3 kgm^-3

Volume = 8m 5m 4m

= 160 m³

To find:

Mass = m = ?

7.5 A student presses her palm by her thumb with a force of 75 N. How much would be the pressure under her thumb having contact area 1.5 cm²? 09107132

Given Data:

Force = F = 75 N

Area = 1.5 cm²

1 cm = 10^-2m

= 1.5 (10^-2m)²

= 1.5 10^-4m²

To find:

Pressure = P = ?

7.6 The head of a pin is a square of side 10 mm. Find the pressure on it due to a force of 20 N. (Board 2014) 09107133

Given Data:

Force = F = 20 N

length = L = 10 mm = 10´10^-3 m

Area = A = LL = 10 10^-310 10^-3

A=110^-4m²

To find:

Pressure = P = ?

7.7 A uniform rectangular block of wood 20 cm 7.5 cm 7.5 cm and of mass 1000 g stands on a horizontal surface with its longest edge vertical. Find
(i) the pressure exerted by the block on the surface 09107134

(ii) density of the wood.

Given Data:

Mass = m = 1000g = 1 kg

Weight = W = F = mg = 110 = 10N

Area = 7.5 cm 7.5 cm

A= 7.5 7.5(10^-2 m)²

A= 56.2510^-4m²

A = 5.62510^-3m²

Volume = V = 7.5 cm 7.5 cm 20cm

= 1125 (10^-2 m)³

= 1125 10^-6m³

= 1.125 10^-3m³

To Find:

Pressure = P = ?

Density = d = ?

7.8 A cube of glass of 5 cm side and mass 306 g, has a cavity inside it. If the density of glass 2.55 gcm^-3. Find the volume of the cavity. 09107135

Given Data

Length = L = 5 cm

Volume of glass cube without Cavity = V¢

Volume = V¢= 5 5 5 125 cm³

Mass = m = 306 g

To Find:

Volume of Cavity = ?

7.9 An object has weight 18 N in air. Its weight is found to be 11.4 N when immersed in water. Calculate its density. Can you guess the material of the object? 09107136

Given Data: (Board 2014)

Weight of object in air = w₁= 18N

Weight of object in water = w₂=11.6N

Loss in weight = W = W₁- W₂

= 18 -11.6 = 6.6 N

Density of water = _w = 1000 kgm^-3

To find: Density of object D = ?

7.10 A solid block of wood of density 0.6 gcm^-3weighs 3.06 N in air. Determine (a) volume of the block (b) the volume of the block immersed when placed freely in a liquid of density 0.9gcm^-3? 09107137

Given Data:

Þ m = 306 g

Density of liquid = = 0.9 gcm^-3

Density of the block = d = 0.6g cm^-3

To Find:

Volume of block air = V = ?

Volume of block in air = ?

Volume of the Block in liquid = V = ?

7.11 The diameter of the piston of a hydraulic press is 30 cm. How much force is required to lift a car weighing 20000 N on its piston if the diameter of the piston of the pump is 3 cm? 09107138

Given data:

Diameter of piston of Hydraulic press

D = 30 cm = 0.3m

Radius of piston of Hydraulic press

R = = m = 0.15m

Area of piston of Hydraulic press A = r² = (0.15)²

Diameter of Piston of pump

d = 3cm = 0.03 m

Radius of Piston of pump

r =

r = = .015m

Area of Piston of Pump = A = R²

= (0.015)²

Weight on larger Piston = F₂ = 20000 N

To Find:

Force to lift the car = F₁ = ?

7.12 A steel wire of cross-sectional area 210^-5m²is stretched through 2 mm by a force of 4000 N. Find the Young’s modulus of the wire .The length of the wire is 2 m.

Given Data: 09107139

Area = A = 210^-5m²

Increase in length = L = 2mm = 210^-3m

Force = 4000 N

Length = L_o= 2m

To Find:

Young Modulus = Y = ?

UNIT 8

THERMAL PROPERTIES

OF MATTER

Q.1 Define Temperature and Heat. (Board 2013-14-16) 09108001

Q.2 Define Internal energy OR what is internal energy of a body? (Board 2014) 09108002

Q.3 Define thermal equilibrium. 09108003

Q.4 Define thermometer. What are the properties of thermometric materials? Also define thermometric substance. (Board 2013) 09108004

Q.5 Explain liquid in glass thermometer. 09108005

Q. 6 What do you mean by lower and upper fixed points? (Board 2015) 09108006

Q.7 In which scales, is temperature measured? Explain. (OR) Explain the different scales of temperatue. (Board 2013-16) 09108007

Q.8 How can we convert temperature from one scale to other? 09108008

Q.9 Explain the specific heat capacity. or Define specific heat. (Board 2014-15) 09108009

Q.10 Write the importance of large specific heat capacity of water. 09108010

Q.11 What is meant by heat capacity? Explain. 09108011

Q.12 Explain change of state in matter with example. 09108012

Q.13 Define fusion point and freezing point. 09108013

Q.14 What is meant by latent heat of fusion? Explain it with experiment. 09108014

Q.15 Define and explain the latent heat of vaporization. Also explain it with experiment.

or Define latent heat of vaporization. (Board 2014) 09108015

Q.16 Define and explain evaporation. What are the factors on which it depends?

(Board 2013-16) 09108016

Q.17 What is meant by thermal expansion? Or Write any two applications of thermal expansion. (Board 2016) 09108017

Q.18 Define and explain Linear Thermal Expansion. 09108018

Q.19 Define and explain Volume Thermal Expansion. 09108019

Q.20 Why gaps are left in railway tracks? (Board 2013) 09108020

Q.21 Why one end of bridges is placed on roller? 09108021

Q.22 Why overhead transmission lines are given a certain amount of Sag? 09108022

Q.23 What are the applications of thermal expansion in our daily life? 09108023

Q.24 What is meant by Bimetal Strip? Write its uses. (Board 2015) 09108024

Q.25 Explain the thermal expansion of liquid. (Board 2014) 09108025

MULTIPLE CHOICE QUESTIONS

8.1 Encircle the correct answer from the given choices:

Exercise MCQs

1. Water freezes at(Board 2013-14) 09108026
(a) 0^oF (b) 32^oF

2. Normal human body temperature is:
(a) 15 ^oC (b) 37 ^oC 09108027

3. Mercury is used as thermometric material because it has: 09108028
(a) uniform thermal expansion (b) low freezing point
(c) small heat capacity (d) all the above properties

4. Which of the following material has large specific heat? 09108029
(a) copper (b) ice

5. Which of the following material has large value of temperature coefficient of linear expansion?
(a) aluminum (b) gold 09108030

6. What will be the value of b for a solid for which a has a value of

2 ´ 10^-5 K^-1? 09108035
(a) 2 x 10^–5 K^–1
(b) 6 x 10^-5 K^-1
(c) 8 x 10^-15 K^-1
(d) 8 x 10^-5 K^-1

7. A large water reservoir keeps the temperature of nearby land moderate due to: 09108036

      (a) low temperature of water
      (b) low specific heat of water
      (c) less absorption of heat
      (d) large specific heat of water

8. Which of the following affects evaporation? (Board 2015) 09108037

      (a) temperature
      (b) surface area of the liquid
      (c) wind

(d) all of the above

Additional MCQs

9. Unit of Specific heat is 09108038

(a) J (b) Jkg^-1

10. The unit of heat is 09108039

(a) kelvin (b) joule (J)

11. Density of water kgm^-3 is: 09108040

(a) 1000 (b) 4200

12. The unit of co-efficient of linear expansion 09108041

(a) K (b) K^-1

13. The relation between co-efficient of linear expansion and volume expansion is (Board 2015) 09108042

(a) a = 3b (b) b = 3a

14. The formula for conversion of Celsius into Kelvin is 09108043

(a)

(b)

(c)

(d)

15. Degree of hotness or coldness of a body is called 09108044

(a) Heat

(b) Internal energy

(d) Potential energy

16. The sum of kinetic energy and potential energy of molecules or atoms is called 09108045

(a) Temperature

(b) Internal energy

(d) Potential energy

17. The energy store in an atom or molecule due to intermolecular force is 09108046

(a) Kinetic energy

(b) Potential energy

(d) G.P.E

18. The freezing point of Mercury is

(a) 49^oC (b) -49^oC 09108047

19. The boiling point of mercury is

(a) -10^oC (b) 150^oC 09108048

20. The upper reference point in thermometer is used to check

(a) melting point 09108049

(b) Freezing point

(d) Steaming point

21. There are types of thermometer.

(a) 1 (b) 2 09108050

22. In Celsius lower reference point is 0^oC while upper reference point is

(a) 212⁰C (b) 180⁰C 09108051

23. Unit of temperature is 09108052

(a) Fahrenheit (b) Centigrade

24. The value of absolute zero Kelvin temperature is 09108053

(a) 273^oC (b) 273K

25. Specific heat of water is Jkg^-1K^-1

(Board 2014) 09108054

(a) 4200 (b) 4000

26. Specific heat of mercury is Jkg^-1K^-1

(a) 138.6 (b) 4200 09108055

27. Alcohol has specific heat Jkg^-1K^-1

09108056

(a) 2700 (b) 4200

28. The formula of heat capacity is

(a) mc (b) mcDq 09108057

29. Boiling point of water is 09108058

(a) 0^oC (b) 100^oC

30. The value of latent heat of fusion ice is 09108059

(a) 3.36 ´ 10^-5Jkg^-1

(b) 3.36 ´ 10⁵Jkg^-1

(d) None of these

31. The value of latent heat of Vaporization of water is 09108060

(a) 2.26 ´ 10⁶Jkg^-1

(b) 3.29 ´ 10⁵Jkg^-1

(d) 3.29 ´ 10^-5Jkg^-1

32. The unit of heat capacity is 09108061

(a) Jkg K (b) JK^-1

33. Which gas is used in spite of Freon gas in refrigerator? (Board 2013)

(a) CO₂ (b) H₂09108062

34. In Fahrenheit scale, upper refrence point is: 09108063

(a) 32°F (b) 212°F

35. In Kelvin scale, lower reference point is: 09108064

(a) 373K (b) 273K

36. In to how many divisions Fahrenheit scale is divided? 09108065

(a) 100 (b) 273

37. Melting point is also known as:

(a) Briling point 09108066

(b) Freezing point

(d) None of these

38. Which gas is replaced by Ammonia in refrigerators: 09108067

(a) Nitrogen (b) Carbon dioxide

39. Which of following is produced in refrigerators by evaporation of a liquefied gas? 09108068

(a) Heating (b) Cooling

40. Kinetic energy of the molecules depends on its: 09108069

(a) Temperature

(b) Surface area

(d) Volume

41. Latent heat of vaporization is denoted by: 09108070

(a) Hl (b) H_m

42. Latent heat of fusion is denoted by:

(a) Hl (b) H_m09108071

43. Bimetal strip is made up of two different metal: 09108072

(a) Copper & iron

(b) Brass & iron

(d) Copper & Nickel

44. Thermostat is a controlling switch:

(a) Heat (b) Temperature 09108073

45. Water on cooling below 4°C begins to: 09108074

(a) Expand (b) Contract

46. When ice is cooled below 0°C it:

(a) Expands (b) Contracts 09108075

47. On heating the strip, ____expands more than ____ respectively. 09108076

(a) Brass, iron

(b) Iron, brass

(d) Brass, copper

48. From following, in which device thermostat is used: 09108077

(a) Electroscope

(b) Electric bell

(d) Radio

49. Evaporation causes: 09108078

(a) Melting (b) Boiling

50. Which flower is known as natural thermometer? 09108079

(a) Rose (b) Brasicca

51. Crocus flower open when the temperature is: 09108080

(a) 23°C (b) 26°C

52. The range of clinical thermometer is:

(a) 90°C-106°C 09108081

(b) 35°C-42°C

(d) 24°C-35°C

53. The changing of a liquid into vapours from the surface of the liquid without heating: 09108082

(a) Cooling

(b) Vaporization

(d) sublimation

54. The unit of rate of conduction:

(a) JS^-1 (b) J

Exercise Question Answers

Q.8.2 Why does heat flow from hot body to cold body? 09108083

Q.8.3 Define the terms heat and temperature.

Q.8.4 What is meant by internal energy of a body? 09108084

Q.8.5 How does heating affect the motion of molecules of a gas? 09108085

Q.8.6 What is a thermometer? Why mercury is preferred as a thermometric substance? 09108086

Q.8.7 Explain the volumetric thermal expansion. 09108087

Q.8.11 What is meant by evaporation? On what factors the evaporation of a liquid depends? Explain how cooling is produced by evaporation. 09108088

Additional Question Answers

Q.1 How does cooling effect produce in Refrigerator? 09108089

Q.2 What is clinical thermometer? What is the use of clinical thermometer ? Write its range. (Board 2013) 09108090

Q.3 What is meant by anomalous expansion of water? (Board 2013) 09108094

Q.4 What is the effect of large water reservoirs on climate? (Board 2014) 09108095

Q.5 Write two scales of temperature. (Board 2014) 09108096

Q.6 Which flower is known as natural thermometer and why? 09108097

Q.7 What is meant by thermal equilibrium? (Board 2015) 09108098

Q.8 Define co-efficient of linear expression. (Board 2014) 09108099

Q.9 Define internal energy. 09108102

Q.10 Define thermometer. 09108103

Q.11 Write the formula to convert scales of temperature from one another.

Q.12 Define specific heat. 09108104

Q.13 Define heat capacity. 09108105

Q.14 Define latent heat of vaporization.

09108106

Q.15 Define thermal expansion. 09108107

Q.16 Define coefficient of volume expansion. 09108108

Q.17 Define bimetallic strip. 09108109

Q.18 What is the freezing and boiling point of mercury? 09108110

Q.19 What is upper and lower fixed point?

09108111

Q.20 Write down the lower and upper fixed point of celcius scales. 09108112

Q.21 Write down the lower and upper fixed point of Fahrenheit scale: 09108113

Q.22 Write down the lower and upper fixed points of Kelvin Scale. 09108114

Q.23 In how many divisions, each temperature scale is divided? 09108115

Q.24 How many times specific heat of water is greater than soil? 09108116

Q.25 What is the benefit of large specific heat of water? 09108117

Q.26 Define fusion point / melting point.

09108118

Q.27 Define freezing point. 09108119

Q.28 Define evaporation. 09108120

Q.29 On what factor kinetic energy of an object depends? 09108121

Q.30 What is the relation between coefficient of linear and volume expansion.

09108122

Q.31 What is thermostat? 09108123

Q.32 How many types of thermal expansion of liquids? 09108124

Q.33 What happens when we touch a hot body? 09108123

Q.34 Why in summer, ice is wrap with cloth or stored in thermos flask? 09108123

Q.35 Why are desert nights colder whereas day very hot? 09108123

MINI EXERCISE

Q.1 Which of the following substances have greater average kinetic energy of its molecules of 10^oC. 09108123

(a) steel (b) copper

Q.2 Every thermometer makes use of some property of material that varies with temperature, name the property used in: 09108123

(a) strip thermometers

(b) mercury thermometers

Q.3 How specific heat differes from heat capacity? 09108123

Q.4 Give two uses of cooling effects by evaporation. 09108123

Q.5 How evaporation differs from vaporization? 09108123

Q.6 Calculate the value of latent heat of fusion of 4kg of ice at 0^oC. 09108135

SOLVED EXAMPLES

Example 8.1

What will be the temperature on Kelvin scale of temperature when it is 20^oC on Celsius scale?

09108008

Example 8.2 (Board 2014-15) 09108009

Change 300K on Kelvin scale into Celsius scale of temperature.

Example 8.3 (Board 2014) 09108010

Convert 50^oC on Celsius scale into Fahrenheit temperature scale.

Example 8.4 (Board 2013-14) 09108011

Convert 100 ^oF into the temperature on Celsius scale.

Examples 8.5

A container has 2.5 litres of water at 20^oC. How much heat is required to boil the water?

09108014

Example 8.6

A brass rod is 1m long at 0^oC. Find its length at 30^oC 09108022

(Co-efficient of linear expansion of brass = 1.9 x 10^-5 K^-1)

Example 8.7

Find the volume of a brass cube at 100^oC whose side is 10cm at 0^oC (Coefficient of linear thermal expansion of brass = 1.9x10^-5K^-1) 09108024

NUMERICAL PROBLEMS

8.1 Temperature of water in a beaker is 50^oC. What is its value in Fahrenheit scale?

Given data: 09108125

Temperature in centigrade = T_c = 50C^o

To Find:

Temperature in Fahrenheit = T_F= ?

8.2 Normal human body temperature is 98.6 ^oF. Convert it into Celsius scale and Kelvin scale. (Board 2013-15) 09108126

Given data:

Temperature in Fahrenheit = T_F = 98.6 F^o

To Find:

Temperature in Celsius Scale =T_c = ?

Temperature in Kelvin Scale =T_k = ?

8.3 Calculate the increase in the length of an aluminum bar 2 m long when heated from 0 ^oC to 20 ^oC. If the thermal coefficient of linear expansion of aluminum is 2.5 ´ 10^-5 K^-1. 09108127

Given data:

Original length = L = 2m

Initial temperature = T₁= 0^oC

= 0+273

= 273 K

Final Temperature = T₂ = 20⁰C

= 20+273 = 293 K

Co-efficient of linear expansion = a

a = 2.5 ×10^-5K^-1

To Find:

Increase in length = L = L-L_o=?

8.4 A balloon contains 1.2m³air at 15 ^oC. Find its volume at 40 ^oC. Thermal coefficient of volume expansion of air is 3.67 x 10^–3 K^–1. 09108128

Given data:

Initial volume = V_o = 1.2 m³

Initial Temperature = T₁= 15^oC

= 15+273

= 288 K

Final Temperature = T₂ = 40^oC

= 40+273

= 313 K

Temperature difference DT = T₂ - T₁ = 313 ‑ 218 = 25K

Coefficient of volume expansion = b

= 3.67 ´ 10^-3K^-1

To find:

Volume = V = ?

8.5 How much heat is required to increase the temperature of 0.5 kg of water from 10 ^oC to 65 ^oC? (Board 2014) 09108129

Given data:

Mass = m = 0.5 Kg

Initial temperature = T₁ = 10^oC.

= 10+273

= 283 K

Final temperature = T₂ = 65^oC

= 65+273

= 338K

Specific heat of water = c = 4200Jkg^-1 K^-1.

To Find

Heat = Q= ?

8.6 An electric heater supplies heat at the rate of 1000 joule per second. How much time is required to raise the temperature of 200 g of water from 20 ^oC to 90 ^oC? 09108130

Given data:

Rate of heat supplied = = 1000Js^–1.

Mass of water = m = 200 g = 0.2 Kg

Specific heat of water = c = 4200J kg^-1 K^-1.

Initial temperature = T_o = 20 ^oC.

= 20+273

= 293 K

Final temperature =T= 90^o = 90+273=363 K

Temperature difference =DT = T - T_o = 363 - 293 = 70K

To Find:

Time = t = ?

8.7 How much ice will melt by 50000 J of heat? Latent heat of fusion of
ice = 336000 Jkg^–1. (Board 2014) 09108131

Given data:

Heat = Q = 50000 J

Latent heat of fusion =H_f = 336000JKg^-1.

To Find:

Mass = m = ?

8.8 Find the quantity of heat needed to melt 100g of ice at -10 ^oC into water at

10 ^oC. 09108132

Given data:

Mass of ice = m = 100g =0.1Kg

Initial temperature = T₁ -10 ^oC = –10+273

= 263 K

Temperature of ice = T₂ = 0 ^oC

= 0 + 273

= 273 K

Final temperature of water = T₃ = 10 ^oC

= 10+273

= 283 K

Specific heat of water = 4200 J kg^-1 K^-1.

Specific heat of ice = C_ice = 2100 Jkg^-1 K^-1.

Latent heat of fusion of ice = H_f

= 336000 Jkg^-1.

To Find:

Heat absorbed by ice = Q = ?

8.9 How much heat is required to change 100 g of water at 100 ^oC into steam? (Latent heat of vaporization of water is 2.26 x 10⁶ Jkg^-1. (Board 2013-15) 09108133

Given data:

Mass of water = m = 100 g = 0.1 kg

Temperature = T = 100 ^oC

= 273+100 = 373 K

Latent heat of vaporization of water = H_v

H_v = 2.26 ´ 10⁶ Jkg^-1.

To Find: Heat = Q ?

8.10 Find the temperature of water after passing 5 g of steam at 100 ^oC through 500 g of water at 10 ^oC.

(Note: Specific heat of water is 4200 Jkg^-1 K^-1, latent heat of vaporization of water is
2.26 x 10⁶ Jkg^-1). 09108134

Given data:

Mass of steam = m, = 5g = =0.005kg

Temperature of steam=T₁=100^oC =100+273 =373K

Initial temperature of water = T₂= 10^oC

T₂ = 10+273

= 283 K

Mass of water = m₂ = 500g

= 0.5 Kg

Latent heat of vaporization of water = H_V = 226000J kg^-1.

Specific heat of water = c =4200 Jkg^-1 K^-1.

To Find:

Temperature of mixture = T = ?

UNIT 9

TRANSFER OF HEAT

Q1. Define heat. Also write its uses. (Board 2014) 09109001

Q.2 How is heat transferred? Explain the process (method) of heat transferring. (Board 2014) 09109002

Q.3 Explain conduction process. (OR) How heat is transfer in solids explain? 09109003

Q.4 Define Thermal Conductivity. What are the factors on which it depends? Explain. 09109004

Q5. What are the uses of conductors and Non conductors? (Board 2015) 09109005

Q6. What measures should be taken to save energy in our houses? 09109006

Q7. Explain convection process. (Board 2016) 09109007

Q8. What is convection currents and uses of Convection currents? 09109008

Q9. Why does sea breeze blow during the day? 09109009

Explain land and sea breezes are examples of convection. (Board 2013-15)

Q10. Why does land breeze blow from land to sea during night? (Board 2015) 09109010

Q11. What causes the glider to remain in air? (Board 2013-14) 09109011

Q12. How do thermals help birds to fly for hours without flapping their wings? 09109012

Q13. Define radiation process. 09109013

Q.14. How does the heat reach us directly from a fireplace? 09109014

Q15. On what factors radiation depends? (Board 2015) 9109015

Q.16 Why does a cup of hot tea become cold after sometime? 09109016

Q.17 Why does a glass of chilled water become hot after sometime? 09109017

Q.18 Explain Emission and Absorption of Radiation. (OR) How various surfaces can be compared by Leslie's cube? (Board 2014) 09109018

Q.19 What is greenhouse effect? (Board 2013-15) 09109019

Q.20 Explain the impact of greenhouse effect in global warming. (Board 2013) 09109020

Q.21 What are the applications and consequences of Radiation? 09109021

MULTIPLE CHOICE QUESTIONS

9.1 Encircle the correct answer from the given choices:

Exercise MCQs

1. In solids, heat is transferred by:

(Board 2015) 09109022

(a) radiation (b) conduction

2. What happens to the thermal conductivity of a wall if its thickness is doubled? (Board 2014-16) 09109023

(a) becomes double

(b) remains the same

(d) becomes one fourth

3. Metals are good conductor of heat due to the: 09109024

(a) free electrons

(b) big size of their molecules

4. In gases, heat is mainly transferred by: (a) molecular collision 09109025

(b) conduction (Board 2013-15)

5. Convection of heat is the process of heat transfer due to the: 09109026

(a) random motion of molecules (b) downward movement of molecules

6. False ceiling is done to: 09109027

(a) lower the height of ceiling (Board 2016) (b) keep the roof clean

7. Rooms are heated using gas heaters by: (a) Conduction only (Board 2014) 09109028

(b) Convection and radiation

8. Land breeze blows from 09109029

(a) sea to land during night

(b) sea to land during the day

9. Which of the following is a good radiator of heat? 09109030

(a) a shinning silvered surface (b) a dull black surface

(d) a shinning colored surface

Additional MCQs

10. There are ways to transfer the heat from one place to another

(Board 2013) 09109031

(a) 1 (b) 2

11. Which one box is used to keep food hot and ice cream cold for long period? 09109032

(a) Iron box

(b) Aluminium box

(b) Plastic box

12. Unit of thermal conductivity is 09109033

(a) WmK (b) W m^-1K^-1

13. Thermal conductivity of iron is

Wm^-1K^-1

(a) 85 (b) 36 09109034

14. Air & water is conductor: 09109035

(a) Poor (b) Good

15. Sea breeze blows from sea to land: during: 09109036

(a) day (b) Night

16. Land breeze from land to sea during:

(a) Day (b) night 09109037

17. The process in which heat is transfer due to actual movement of molecule is called: (Board 2014) 09109038

(a) Conduction (b) Radiation

18. The example of bad conductor is:

(Board 2014) 09109039

(a) Wool (b) Copper

19. Flow of thermal energy from hot body cold body is called: 09109040

(a) specific heat (b) Latent heat

20. Wood, cork, cotton, wool, rubber are the examples of : 09109041

(a) conductor (b) Thermal conductor

21. In buildings central heating system works on the process of: 09109042

(a) Convection (b) Radiation

22. The main source of energy in the universe is: 09109043

(a) Moon (b) Stars

23. The bad conductor of heat is: 09109044

(a) Iron (b) Copper

24. Leslie cube have faces: 09109045

(a) 2 (b) 3

25. More radiation is reflected by the surface: 09109046

(a) White (b) Coloured

26. The quantity of heat absorbed by the body depends upon: 09109047

(a) Colour of surface

(b) Nature of surface

(d) Both a & b

27. Dull black surface is a best: 09109048

(a) Emitter (b) Absorber

28. Shining silvered surface is a best:

(a) Emitter (b) Absorber 09109049

29. Leslie’s cube is a box of: 09109050

(a) Metal (b) None-metals

30. Leslie’s cube is filled with: 09109051

(a) Cold water (b) Hot water

31. Glass and transparent polythene sheets

allow radiations of wavelength to pass through them: 09109052

(a) Long (b) Medium

32. Which gas behaves as glass or polythene to radiation: 09109053

(a) Nitrogen (b) Hydrogen

33. Thermos flask, is used to maintain:

(a) Heat (b) Temperature 09109054

34. Land and sea breezes are the results of:

(a) Conduction 09109055

(b) Convection

(d) Conduction and radiation

35. Feathers of bird give good thermal:

(a) Conduction (b) Insulation 09109056

36. On heating become Air: 09109057

(a) Heavier (b) Lighter

Exercise Answer Questions

Q.9.2 Why metals are good conductors of heat? (Board 2014) 09109058

Q.9.3 Explain why: 09109059

(a) A metal feels colder to touch than wood kept in a cold place?

(b) Land breeze blows from land towards sea? 09109060

(c) Double walled glass vessel is used in thermos flask? 09109061

(d) Deserts soon get hot during the day and soon get cold after sunset? 09109062

Q.9.4 Why conduction of heat does not take place in gases? 09109063

Q.9.5 What measures do you suggest to conserve energy in houses? 09109064

(Board 2016)

Q.9.6 Why transfer of heat in fluids take place by convection? 09109065

Q.9.7 What is meant by convection current? (Board 13,14) 09109066

Q.9.8 Suggest a simple activity to show convection of heat in gases not given in the book. 09109067

Q.9.9 How does heat from sun reaches on the earth? (or) How does heat reach us from the sun? (Board 2016) 09109068

Q.9.10 How can various surfaces be compared by a Leslie cube? 09109069

Q.9.11 What is greenhouse effect? 09109070

Q.9.12 Explain the impact of greenhouse effect in global warming. 09109071

Additional Answers Questions

Q.1 Why are Styrofoam boxes used to keep food hot or ice cream cold for a long time?

09109072

Q.2 Why do we use thermos flask? 09109073

Q.3 Why it is not advisible to wear dark colours in summer? (Board 2014) 09109074

Q.4 What is thermos flask? (Board 2013) 09109075

Q5. Why sauce pans are made of metal? (Board 2014) 09109076

Q.6 Describe the effect of length of the solid on thermal conductivity? 09109077

Q.7 Define Conduction, convection and radiation. 09109078

Q.8 Define connection. 09109079

Q.9 Define thermal conductivity. 09109080

Q.10 Why we wear light colours clothes in summer? 09109081

Q.11 What is Global warming. 09109082

Q.12 How does heat flow from hot to cold parts in metals so rapidly than non-metals? 09109083

Q.13 Why a balloon inflated with hot air rises up? 09109084

Q.14 Why transfer of heat in fluids takes place by convections? 09109085

Q.15 How do the land and sea breeze help to keep the temperature moderate in coastal areas? 09109086

SOLVED EXAMPLES

EXAMPLE 9.1

The exterior brick wall of a house of thickness 25 cm an area 20 m². The temperature inside the house is 15^oC and outside is 35^o C. Find the rate at which thermal energy will be conducted through the wall, the value of k for bricks is 0.6 W m^-1 K^-1. 09109087

NUMERICAL PROBLEMS

9.1 The concrete roof of a house of thickness 20 cm has an area 200 m². The temperature inside the house is 15^oC and outside is 35^oC. Find the rate at which thermal energy will be conducted through the roof. The value of k for concrete is 0.65 Wm^-1K^-1. 09109088

Given data:

Length=L = 20cm = = 0.2m

Area=A = 200m²

Outside temperature = T₁ = 35^oC

= 35 + 273 = 308K

Inside temperature = T₂ = 15^oC

= 15 + 273 = 288K

DT = T₂ - T₁

= 308 - 288 = 20 K

DT = 20 K

Thermal conductivity k = 0.65Wm^-1K^-1

To Find: Rate of flow = ?

9.2 How much heat is lost in an hour through a glass window measuring 2.0 m by 2.5 m when inside temperature is 25^oC and that of outside is 5^oC, the thickness of glass is 0.8 cm and the value of k for glass is 0.8 Wm^-1K^-1? 09109089

Given Data:

Time = t = 1 hour = 3600 sec

Area A = 2 ´ 2.5 = 5m²

Length L = 0.8 cm =

T₁ = 25^oC = 25 + 273 = 298K

T₂ = 5C⁰ = 5 + 273 = 278K

DT = T₁ - T₂

= 298 - 278

DT = 20 K

Thermal conductivity = 0.8wn^-1k^-1

To Find: heat loss = Q = ?

Causative

9th Physics Full book

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