**Extra Questions for Class 9 Science Chapter 11 Work and Energy**

Here we are providing extra questions for class 9 science **chapter 11 work and energy**. Various type of questions are provided. These includes very short answer type questions, short answer type questions and long answer type questions as well. These questions are important for exam as well. You will be able to score more in your exams by practicing these questions.

**Very Short Answer Type Question (VSA)**

1. Seema tried to push a heavy rock of 100 kg for 200 s but could not move it. Find the work done by Seema at the end of 200 s.

2. At what speed a body of mass 1 kg will have a kinetic energy of 1 J?

3. Define 1 Joule of work.

4. Identify the energy possessed by a rolling stone.

5. Identify the kind of energy possessed by a running athlete.

6. What would be the amount of work done on an object by a force, if the displacement of the

object is zero?

7. How much work is done by a weight lifter when he holds a weight of 80 kgs on his shoulders

for two minutes?

8. A car and a truck are moving with the same velocity of 60 km/hr. Which one has more kinetic

energy? (Mass of truck > Mass of car).

9. A body is thrown vertically upwards. Its velocity goes on decreasing. Write the change in kinetic energy when its velocity becomes zero.

10. A force of 10 N moves a body with a constant speed of 2 m/s. Calculate the power of the

body.

11. What will be the kinetic energy of a body when its mass is made four times and the velocity is

doubled?

12. A freely falling object eventually stops on reaching the ground. What happens to its kinetic

energy on reaching the ground?

13. State the energy conversions in a dry cell.

14. What is the work done by the Earth in moving around the Sun?

15. A coolie is walking on a railway platform with a load of 30 kg on his head. How much work is done by coolie?

16. How many times does the kinetic energy of a body become when its speed is doubled?

17. In an oscillating pendulum, at what positions the potential and kinetic energy are maximum?

18. Define S.I. unit of work?

19. Name the type of energy possessed by a raised hammer?

20. What is the form of energy possessed by a running car?

21. State the value of commercial unit of electrical energy in joules?

22. A 2 m high person is holding a 25 kg trunk on his head and is standing at a roadways bus-terminus. How much work is done by the person?

23. A horse of mass 210 kg and a dog of mass 25 kg are running at the same speed. Which of

the two possesses more kinetic energy? How?

24. If the speed of the body is halved, what is the change in its kinetic energy?

25. Moon is experiencing a gravitational force due to Earth and is revolving around the Earth in

a circular orbit. How much work is done by moon?

26. Give the formula for calculating work done. What is the SI unit of work?

27. Define 1 watt of power.

28. A man holding a bucket of water on his head stands stationary. Is he doing any work? Give

reason.

29. Name the type of energy possessed by the following? (i) Stretched slinky (ii) Speeding car 30.

30. Write the formula to measure the work done, if the displacement of the object is at an angle of 90° to the direction of force.

31. If we lift a body of mass 70 g vertically upwards 10 m then calculate the force required to lift the body (g = 10 ms^{–2}).

32. At what rate is electrical energy consumed by a bulb of 60 watt?

33. Give an example of a body having potential energy due to change of shape.

34. When is work done by a force zero?

35. If the heart works 60 joules in one minute, what is its power?

36. Name the term used for the sum of kinetic energy and potential energy of a body.

37. Write the observed energy transformation that takes place at thermal power station.

38. A 40 kg girl is running along a circular path of radius 1 m with a uniform speed. How much

work is done by the girl in completing one circle?

39. Calculate the work done when a force of 15 N moves a body by 5 m in its direction.

40. Write the S.I. unit of power.

41. A student is writing a three hours science paper. How much work is done by student? Give reasons to your answer.

42. When displacement is in a direction opposite to the direction of force applied, what is the type of work done?

43. What is the work done against gravity when a body is moved horizontally along a frictionless

surface?

**Short Answer Type Questions**

1. The velocity of a body moving in a straight line is increased by applying a constant force F, for some distance in the direction of the motion. Prove that the increase in the kinetic energy of the body is equal to the work done by the force on the body.

2. In each of the following a force F, is acting on an object of mass m. The direction of displacement is from west to east shown by longer arrow. Observe the diagrams carefully and state whether work done by force is –ve, +ve or 0.

3. (a) Define 1 watt.

(b) An electric bulb of 60 W (sixty watt) is used for 6 (six) hours per day. Calculate the

units of energy consumed in one day by the bulb.

4. (a) Is it possible that a force is acting on a body but still work done is zero? Explain giving

one example.

(b) Two bodies of equal masses move with uniform velocities of v and 3v respectively. Find the ratio of their kinetic energies.

5. (a) How much work is done when a force of 1 N moves a body through a distance of 1 m in its direction?

(b) Is it possible that a force is acting on a body but still the work done is zero? Explain giving one example.

6. (a) What is meant by potential energy? Is potential energy a vector or scalar quantity?

(b) Given one example of a body having potential energy.

**Long Answer Type Questions**

1. A mass of 10 kg is dropped from a height of 50 cm. Find its :

(a) potential energy just before dropping

(b) kinetic energy just on touching the ground (c) velocity with which it hits the ground [Given g = 10 ms^{–2}]

2. (i) Define the term potential energy. Write the S.I. unit of potential energy.

(ii) A body of mass 50 kg is situated at a height of 10 m. What is its potential energy (Given g = 10 ms^{–2})

3. (i) Define power. Mention its S.I. unit.

(ii) A body of mass 50 kg runs up a staircase of 40 steps in 8 s. If the height of each step is 15 cm, find his power. (Given, g = 10 ms^{–2})

4. A light and heavy object have the same momentum, find out the ratio of their kinetic energies. Which one has a larger kinetic energy?

5. (a) Can any object have momentum even if its mechanical energy is zero? Explain why?

(b) A ball is dropped from a height of 10 m. If energy of the ball reduces by 40% after striking the ground, how high can the ball bounce back? (g = 10 m/s^{2}).

*You may also like:*

Extra questions for other chapters of class 9 science is given below.

Chapter 3 Atoms and Molecules

Chapter 4 Structure of Atom

Chapter 10 Gravitation

Chapter 11 Work and Energy

Chapter 13 Why Do We Fall Ill?