WORK AND ENERGY

WORK AND ENERGY

VERY SHORT ANSWER TYPE QUESTIONS (VSAQ)

1. What does "work" mean in scientific terms? Ans :- In science, "work" is done when a force acts on an object and c...

11. Why is energy important for life? Ans :- Energy is essential for all life activities and processes, making it im...

21. A spring which has been kept compressed by tying its ends together is allowed to be dissolved in an acid. What happe...

31. A spring which is kept compressed by tying its ends together is allowed to be dissolved in an acid. What happens to...

41. Define power. Ans :- The rate by which work is done refers to power. It is expressed by P. Power = Work done/Tim...

SHORT ANSWER TYPE QUESTIONS (SAQ)

1. What is the difference between the everyday meaning of "work" and its scientific meaning? Ans :- In everyday lang...

2. What are the two conditions necessary for work to be done? Give an example for each condition. Ans :- The two con...

3. Explain why holding a heavy load without moving does not count as work in scientific terms. Ans :- Holding a heav...

4. How is work calculated when a constant force acts on an object? Ans :- When a constant force acts on an object,...

5. What does it mean when work is considered positive? Ans :- Work is considered positive when the force acting on a...

6. Explain 1 joule of work done. Ans :- When a force of 1 Newton (N) is exerted on an object, and the object moves a...

7. What will be the expression for the work done when a force acts on an object in the direction of its motion. Ans :-...

8. How much work is done in ploughing a 15 m long field when a pair of bullocks applies a force of 140 N on the plough?...

9. The force acting on the object is 7 N, and the displacement of the object occurs in the direction of the force is 8 m...

10. What is the significance of negative work in a physical context? Ans :- Negative work occurs when a force acts i...

11. What are some main sources of energy on Earth? Ans :- The primary source of energy on Earth is the Sun, which pr...

12. How is energy defined in science, and how is it measured? Ans :- In science, energy is defined as the capacity t...

13. What happens to energy when work is done on an object? Ans :- When work is done on an object, the object that do...

14. How can we express the relationship between work done and kinetic energy? Ans :- The kinetic energy of an object...

15. What does the law of conservation of energy state? Ans :- The law of conservation of energy states that energy c...

16. How does a pendulum illustrate the conservation of energy? Ans :- A pendulum shows the conservation of energy th...

17. The output power of the electric heater is 1500 watts. How much energy does it consume in 10 hours? Ans :- Pow...

18. An object of mass m moves at a constant speed v. How much work does the subject need to do to make it stable? An...

19. Describe the law of conservation of energy. Ans :- The law of conservation of energy states that: i. Energy cann...

20. Calculate the energy (in kilowatt hours) consumed by four 500 W devices in 10 hours. Ans :- Since, Energy = Powe...

21. A large force acting on an object, and the displacement of that object is zero, what will be the work done? Ans...

22. What do you understand about average power? Ans :- An agent may not always perform the same amount of work withi...

23. The law of conservation of energy is explained by discussing the energy changes that occur when we move the pendulum...

24. What kind of energy transformation takes place when a body is dropped from a certain height? Ans :- As a body fa...

25. If an electric appliance is rated 1000 W and is used for 2 hours. Calculate the work done in 2 hours. Ans :- Wor...

26. A man of mass 62 kg sums up a stair case of 65 steps in 12 s. If height of each step is 20 cm, find his power. Ans...

27. How is work done by a force measured? A porter lifts a luggage of 20 kg from the ground and puts it on his head 1.7...

28. The velocity of a body moving in a straight line is increased by applying a constant force F, for some distance in t...

29. An athlete weighing 60 kg runs up a staircase having 10 steps each of 1 m in 30 sec. Calculate power (g = 9.8ms–1)....

30. An electric kettle of 500W is used to heat water everyday for 2 hours. Calculate the number of unit of electrical en...

31. A body of 5 kg raised to 2 m find the work done. Ans :- The work done to raise a body = PE = mgh = 5 kg × 9....

32. An engine work 54,000 J work by exerting a force of 6000 N on it. What is the displacement of the force? Ans :-...

33. What are potential and kinetic energy? Ans :- Potential energy is the stored energy an object has due to its pos...

34. When an arrow is shot from its bow, it has kinetic energy. From where does it get the kinetic energy? Ans :- A s...

35. A man rowing a boat upstream is at rest with respect to the shore. Is he doing work? Ans :- The man is performin...

36. Calculate the cost of using a 2 kWh immersion rod for heating water in a house for one hour each day for 60 days if...

37. Can any object have mechanical energy even if its momentum is zero? Explain. Ans :- Yes, mechanical energy consi...

38. How much work is done by a force of 10 N in moving an object through a distance of 4 m in the direction of the force...

39. The work done in lifting a box on to a platform does not depend upon how fast it is lifted up. Explain your answer g...

40. A body moves along a circular path. How much work is done in doing so? Explain. Ans :- In the case of a body mov...

41. A work of 4900 J is done on load of mass 50 kg to lift it to a certain height. Calculate the height through which th...

42. A body performs no work. Does it imply that the body possesses no energy? Ans :- When a body is not performing a...

43. A force of 10N causes a displacement of 2 m in a body in its own direction. Calculate the work done by force. Ans...

44. The power of a heart which beats 72 times in a minute is 1.2 kW. Calculate the work done by heart for each beat. (1...

45. Is it possible that a body be in accelerated motion under a force acting on the body, yet no work is being done by t...

46. How much force is applied on the body when 150 joule of work is done in displacing the body through a distance of 10...

47. What type of energy is stored in the spring of a watch? Ans :- When we wind a watch, the configuration of its sp...

48. An object is thrown at an angle to the ground, moves along a curve and falls back to the ground. The start and end p...

49. An object having 10 kg weight is moved from point A to point B on the table. If the distance between A and B is hori...

50. Does energy transfer occur when you push a huge rock with all your strength without moving it? Where did the energy...

51. What is kinetic energy, and how does it relate to motion? Ans :- Kinetic energy is the energy that an object pos...

52. What factors affect the amount of kinetic energy an object has? Ans :- The amount of kinetic energy an object ha...

53. A household uses 250 units of energy in a month. How much energy is used by that house in joules? Ans :- Energy...

54. A body of mass 2 kg is moving with a speed of 20 m/s. Find the kinetic energy. Ans :- KE = 0.5 mv2 = 0.5 × 2...

55. The potential energy of an object decreases gradually in a free fall. How does this violate the law of conservation...

56. A hammer of mass 1 kg falls freely from a height of 2 m. Calculate (I) The velocity and (II) The kinetic energy of t...

57. A rickshaw puller pulls the rickshaw by applying a force of 100 N. If the rickshaw moves with constant velocity of 3...

58. (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 pos...

LONG ANSWER TYPE QUESTIONS (LAQ)

1. Discuss the importance of understanding the scientific definition of work, and explain how it differs from everyday u...

2. Explain the concept of work done by a constant force, including how it is calculated, its units, and the significance...

3. Explain the concept of energy, its sources, and its significance in doing work. Include how it is measured and give e...

4. When a force retards the motion of a body, what is the nature of work done by the force? State reason. List two examp...

5. When is the work done by a force said to be negative ? Give one situation in which one of the forces acting on the ob...

6. Give one example each of potential energy (i) due to position (ii) due to shape. Ans :- (i) Potential Energy Due...

7. (a) Under what conditions work is said to be done? (b) A porter lifts a luggage of 1.5 kg from the ground and puts it...

8. Four persons jointly lift a 250 kg box to a height of 1 m and hold it. (i) Calculate the work done by the persons in...

9. Get the expression of the potential energy of an object. Calculate PE for a body of 10 kg which is resting at a heigh...

10. A person weighing 50 kg climbs the stairs with a height difference of 5 meters, within 4 seconds. (a) What kind of...

11. If a force of 12.5 N is applied to complete a work of 100 J, what is the distance covered by the force? Ans :-...

12. A car weighing 1800 kg is moving at a speed of 30 m/s when braking. If the average braking force is 6000 N, it is de...

NCERT SOLUTION

Page No. 115 1. A force of 7 N acts on an object. The displacement is, say 8 m, in the dire...

Page No. 116 1. When do we say that work is done? 2. Write an expression for the...

Page No. 119 1. What is the kinetic energy of an object? Ans :- The kinetic ene...

Page No. 123 1. What is power? 2. Define 1 watt of power....

Page No. 124 Exercises 1. Look at the activities listed below. Reason out whether or not wo...

Page No. 125 2. An object thrown at a certain angle to the ground moves in a curved path and...

4. Certain force acting on a 20 kg mass changes its velocity from 5 m s -1 to 2 m s -1. Calculate the work done by th...

5. A mass of 10 kg is at a point A on a table. It is moved to a point B. If the line joining A and B is horizontal,...

6. The potential energy of a freely falling object decreases progressively. Does this violate the law of conservatio...

7. What are the various energy transformations that occur when you are riding a bicycle? Ans :- When rid...

10. An object of mass 40 kg is raised to a height of 5 m above the ground. What is its potential energy? If the obje...

11. What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer....

13. A person holds a bundle of hay over his head for 30 minutes and gets tired. Has he done some work or not? Justif...

14. An electric heater is rated 1500 W. How much energy does it use in 10 hours? Ans :- Th...

15. Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulu...

16. An object of mass, m is moving with a constant velocity, v. How much work should be done on the object in order...

17. Calculate the work required to be done to stop a car of 1500 kg moving at a velocity of 60 km/h? Ans :-...

19. Soni says that the acceleration in an object could be zero even when several forces are acting on it. Do you agr...

20. Find the energy in kW h consumed in 10 hours by four devices of power 500 W each. Ans :- T...

21. A freely falling object eventually stops on reaching the ground. What happens to its kinetic energy? Ans...

SUMMARY

Introduction In the past, we talked about how things move, what causes them to move, and the effect of gravity. Now,...

What is Work? The term "work" has different meanings in everyday life compared to its meaning in science. Let’s explore...

Scientific Conception of Work In science, we have a specific way of defining work. Let’s look at a few examples to unde...

Work Done by a Constant Force In science, work is defined as the amount of energy transferred when a force acts on an o...

Energy 1. Importance of Energy: Life depends on energy, and our demand for it is constantly increasing. 2. Main Sources...

Forms of Energy Energy exists in various forms in our world, each serving different purposes. Here are the main forms...

Kinetic Energy Kinetic energy is the energy an object has because it is moving. Here’s a breakdown of key points about k...

Potential Energy 1. Definition: Potential energy is the stored energy in an object due to its position or arrangement....

Gravitational Potential Energy ❑ Definition: Gravitational potential energy is the energy an object has due to its...

Law of Conservation of Energy 1. Definition: The law of conservation of energy states that energy cannot be created or d...

Rate of Doing Work 1. Definition of Power: Power is the rate at which work is done or energy is transferred. It measure...