Work, Energy, and Power Mock Test – Class 11 Physics

1. A block moves to the right. A force acts to the right and a friction force acts to the left. The net work on the block is

2. A car engine supplies useful power while the resistive force is . At what speed can the car move steadily on a level road?

3. A block moves east. A force of acts west during this motion. The work done by this force is

4. A heavy box is pressed against a wall with a horizontal force, but the box does not move. The mechanical work done by the pressing force on the box is

5. A particle has total mechanical energy . At a certain position, its potential energy is . Its kinetic energy at that position is

6. A claim says, "If total mechanical energy is conserved, kinetic energy must be constant." The best correction is that

7. A statement says, "Potential energy at a point must be uniquely fixed by nature, so choosing a different zero level changes the physics." The best correction is that

8. A block starts from rest and slides down a rough incline through a vertical height of . If friction does of work, what is the kinetic energy of the block at the bottom? Take .

9. A stationary body explodes into three fragments. The vector momenta of two fragments are and along the same straight line. The momentum of the third fragment is

10. A ball strikes a fixed wall normally with speed . If the coefficient of restitution is , the speed of rebound is

11. A person holds a heavy suitcase at a fixed height for several seconds. In the elementary mechanical sense, the work done on the suitcase by the person's upward force is

12. Study the table about power and energy.

The row that needs correction is

13. A ball is dropped from and rebounds from a fixed floor with . Taking , the kinetic energy just after the first rebound is

14. A collision is analysed using momentum conservation, kinetic energy comparison, and coefficient of restitution. Which summary is most accurate?

15. A spring-block system has , , and amplitude on a smooth horizontal surface. The maximum speed of the block is

16. The following statements compare collisions and explosions.
I. In an isolated collision, total momentum is conserved.
II. In an isolated explosion, total momentum is conserved.
III. In an inelastic collision, kinetic energy may decrease.
IV. In an explosion, kinetic energy may increase due to internal energy release.
The true statements are

17. A body of mass slows from speed to rest because of a constant resistive force. The magnitude of net work done by the resistive force is

18. A body starts from rest under a variable net force. The area under its graph from to is . If the mass is , its speed at is

19. A machine receives input energy at the rate and delivers useful output energy at the rate . The efficiency of the machine is

20. A ball moves from point P to point Q near Earth's surface. Point Q is lower than point P. If the mass is and , the work done by gravity is

21. A body is displaced by while two constant forces and act on it. The net work may be written as

22. When a force along the -axis changes with position, the work done from to is found by

23. A head-on collision is being checked for consistency. The initial velocities are and , while the final velocities are and . The value of is

24. Study the table for a curve.

The row that needs correction is

25. A cart moving at collides elastically with a stationary cart on a straight frictionless track. The final velocity of the cart is

26. A collision record shows that the total momentum before and after collision is the same, but the final kinetic energy is smaller than the initial kinetic energy. The collision is best classified as

27. A spring force is called restoring because it

28. In a one-dimensional elastic collision, the two conservation equations used together are

29. Two motors lift the same load through the same height. Motor P takes , while motor Q takes . The ratio of their average powers is

30. A spring is stretched slowly from its natural length by . If , the work done by the external agent is

31. A force is called non-conservative when the work done by it between two points

32. Work and energy share the same SI unit because

33. A body moves from to . The net work done on the body is

34. A object moves with speed . Its kinetic energy is

35. A ball of mass is dropped from rest from a height of . Taking and neglecting air resistance, its speed just before hitting the ground is

36. Mechanical energy of a system is commonly written as

37. A particle moves under a conservative force in one dimension. At two positions, the potential energies are and . The work done by the conservative force from P to Q is

38. A particle of mass moves in a potential-energy field with total energy . At position P, ; at position Q, . The speed is greater at

39. A stone is lifted vertically upward through a height near Earth's surface. The work done by gravity on the stone is

40. A block is pulled by a force that makes above the horizontal while the block moves horizontally. If , displacement is , and , the work done by the pulling force is

41. The work-energy theorem is especially useful in a mechanics problem when the known information mainly involves

42. A object is raised from to above the floor. Taking , the change in gravitational potential energy is

43. A body moves along the -axis under a variable net force. The graph has three equal-width regions.

The total change in kinetic energy is

44. For a conservative force in one dimension, the force is related to potential energy by

45. A block compresses a spring from to . If , the work done by the block on the spring during slow compression is

46. Two bodies have the same momentum magnitude. Body P has mass , and body Q has mass . The kinetic energy of P compared with Q is

47. A net force acts on a body and does zero net work over a displacement. The work-energy theorem implies that

48. Read the case below and answer the question.

If cart Q has mass , its speed is

49. A machine rated works for . The energy transferred is

50. The dimensions of work and energy are obtained from force multiplied by displacement. The dimensional formula is