Class 9 Science Chapter 7 | MCQ

NCERT Class 9 Science MCQ | Chapter 7: Work, Energy and Simple Machines

1. In science, work is done by a force when the object:
(A) Is displaced in the direction of the force
(B) Remains stationary
(C) Changes colour
(D) Changes temperature
Answer: (A)

2. The SI unit of work is:
(A) Newton
(B) Joule
(C) Watt
(D) Metre
Answer: (B)

3. One joule of work is done when a force of 1 N displaces an object by:
(A) 1 cm
(B) 10 m
(C) 1 m in the direction of force
(D) 1 km
Answer: (C)

4. The mathematical expression for work done by a constant force acting in the direction of displacement is:
(A) W = F/s
(B) W = F × s
(C) W = mgh
(D) W = ma
Answer: (B)

5. If the force acting on an object is zero, the work done by the force is:
(A) Maximum
(B) Negative
(C) Positive
(D) Zero
Answer: (D)

6. If there is no displacement of an object, the work done on it is:
(A) Zero
(B) Maximum
(C) Negative
(D) Infinite
Answer: (A)

7. A person pushes a rigid wall, but the wall does not move. The work done on the wall is:
(A) Positive
(B) Negative
(C) Zero
(D) Maximum
Answer: (C)

8. When force and displacement are perpendicular to each other, the work done by the force is:
(A) Positive
(B) Negative
(C) Zero
(D) Infinite
Answer: (C)

9. A girl carries a box horizontally while applying an upward force on it. The work done by the upward force on the box is:
(A) Positive
(B) Negative
(C) Zero
(D) Maximum
Answer: (C)

10. When force and displacement are in the same direction, the work done is:
(A) Positive
(B) Negative
(C) Zero
(D) Undefined
Answer: (A)

11. When force acts opposite to the displacement of an object, the work done is:
(A) Zero
(B) Positive
(C) Negative
(D) Infinite
Answer: (C)

12. A goalkeeper stops a moving football by applying a force opposite to its motion. The work done by the goalkeeper on the ball is:
(A) Positive
(B) Negative
(C) Zero
(D) Infinite
Answer: (B)

13. The area under a force-displacement graph represents:
(A) Power
(B) Energy
(C) Work done
(D) Acceleration
Answer: (C)

14. If a constant force of 10 N displaces an object by 2 m in the direction of force, the work done is:
(A) 5 J
(B) 12 J
(C) 20 J
(D) 8 J
Answer: (C)

15. Energy is defined as the:
(A) Rate of doing work
(B) Capacity to do work
(C) Force acting on an object
(D) Displacement produced by force
Answer: (B)

16. The SI unit of energy is:
(A) Watt
(B) Newton
(C) Joule
(D) Pascal
Answer: (C)

17. According to the work-energy theorem, work done on an object is equal to:
(A) Its mass
(B) Change in its energy
(C) Its acceleration
(D) Its velocity
Answer: (B)

18. When positive work is done on an object, it generally:
(A) Loses energy
(B) Gains energy
(C) Loses mass
(D) Stops immediately
Answer: (B)

19. Which of the following is a form of energy?
(A) Chemical energy
(B) Force
(C) Displacement
(D) Acceleration
Answer: (A)

20. The energy possessed by an object due to its motion is called:
(A) Potential energy
(B) Chemical energy
(C) Kinetic energy
(D) Nuclear energy
Answer: (C)

21. The kinetic energy of an object of mass m moving with velocity v is:
(A) mv
(B) mgh
(C) 1/2 mv²
(D) ma
Answer: (C)

22. If the velocity of an object is doubled, its kinetic energy becomes:
(A) Two times
(B) Three times
(C) Four times
(D) Half
Answer: (C)

23. If the mass of an object is doubled while its velocity remains unchanged, its kinetic energy becomes:
(A) Half
(B) Double
(C) Four times
(D) One-fourth
Answer: (B)

24. Kinetic energy has:
(A) Direction only
(B) No direction
(C) Both magnitude and direction
(D) Only negative value
Answer: (B)

25. If negative work is done on an object and its velocity decreases, its kinetic energy:
(A) Increases
(B) Decreases
(C) Remains unchanged
(D) Becomes infinite
Answer: (B)

26. The energy stored in an object due to its deformation or due to the relative position of objects in a system is called:
(A) Kinetic energy
(B) Potential energy
(C) Sound energy
(D) Thermal energy
Answer: (B)

27. The potential energy of an object of mass m at height h near the Earth’s surface is:
(A) mv
(B) ma
(C) mgh
(D) 1/2 mv²
Answer: (C)

28. A 2 kg object is raised to a height of 5 m. Taking g = 10 m/s², its potential energy is:
(A) 10 J
(B) 50 J
(C) 100 J
(D) 200 J
Answer: (C)

29. If the height of an object above the Earth’s surface is doubled, its gravitational potential energy becomes:
(A) Half
(B) Double
(C) Four times
(D) Unchanged
Answer: (B)

30. A stretched spring possesses:
(A) Elastic potential energy
(B) Only kinetic energy
(C) Nuclear energy
(D) Sound energy
Answer: (A)

31. When a freely falling object moves downward, its:
(A) Potential energy increases and kinetic energy decreases
(B) Potential energy decreases and kinetic energy increases
(C) Both potential and kinetic energy decrease
(D) Both remain constant
Answer: (B)

32. The sum of kinetic energy and potential energy of an object is called:
(A) Thermal energy
(B) Chemical energy
(C) Mechanical energy
(D) Electrical energy
Answer: (C)

33. In the absence of external forces, the mechanical energy of a freely falling object:
(A) Increases continuously
(B) Decreases continuously
(C) Remains constant
(D) Becomes zero
Answer: (C)

34. At the highest point of a freely falling object that was initially released from rest, its kinetic energy is:
(A) Maximum
(B) Zero
(C) Equal to potential energy
(D) Infinite
Answer: (B)

35. At the highest point of a freely falling object, its gravitational potential energy is:
(A) Zero
(B) Minimum
(C) Maximum
(D) Negative
Answer: (C)

36. A child slides down a frictionless slide from height h. The speed at the bottom depends mainly on:
(A) The mass of the child
(B) The colour of the slide
(C) The height h
(D) The shape of the child
Answer: (C)

37. Power is defined as:
(A) Work done per unit time
(B) Force per unit mass
(C) Energy multiplied by time
(D) Displacement per unit force
Answer: (A)

38. The SI unit of power is:
(A) Joule
(B) Newton
(C) Watt
(D) Kilogram
Answer: (C)

39. One watt is equal to:
(A) 1 J/s
(B) 1 N/m
(C) 1 J × s
(D) 1 kg/m
Answer: (A)

40. A person does 600 J of work in 3 s. The power developed is:
(A) 100 W
(B) 200 W
(C) 300 W
(D) 1800 W
Answer: (B)

41. One horsepower is approximately equal to:
(A) 100 W
(B) 500 W
(C) 746 W
(D) 1000 W
Answer: (C)

42. A simple machine helps us perform a task by changing:
(A) The total amount of work required
(B) The magnitude or direction of the force required
(C) The mass of the object
(D) The gravitational constant
Answer: (B)

43. The force applied to a simple machine is called:
(A) Load
(B) Effort
(C) Fulcrum
(D) Resistance
Answer: (B)

44. The force that needs to be overcome by a machine is called:
(A) Effort
(B) Load
(C) Fulcrum
(D) Power
Answer: (B)

45. Mechanical advantage is defined as:
(A) Effort/Load
(B) Load/Effort
(C) Load × Effort
(D) Load + Effort
Answer: (B)

46. A fixed pulley mainly helps by:
(A) Reducing the mass of the load
(B) Increasing the weight of the load
(C) Changing the direction of effort
(D) Creating energy
Answer: (C)

47. The mechanical advantage of an ideal fixed pulley is:
(A) 0
(B) 1
(C) 2
(D) Greater than 2
Answer: (B)

48. An inclined plane helps to move a heavy load to a higher level by:
(A) Increasing the effort required
(B) Reducing the force required by increasing the distance over which it acts
(C) Increasing the weight of the object
(D) Eliminating all work
Answer: (B)

49. In a lever, the fixed point about which the lever rotates is called:
(A) Load
(B) Effort
(C) Fulcrum
(D) Load arm
Answer: (C)

50. Which of the following is a Class II lever?
(A) Scissors
(B) Tweezers
(C) Lemon squeezer
(D) Broom
Answer: (C)