9th class Physics, Chapter 5: Work, Energy and Power MCQs

1. Work done is maximum when the angle between the force F and the displacement d is:

1. (A) 0° ✓
2. (B) 30°
3. (C) 60°
4. (D) 90°

2. A joule can also be written as:

1. (A) kg m s⁻²
2. (B) kg m s⁻¹
3. (C) kg m² s⁻³
4. (D) kg m² s⁻² ✓

3. The SI unit of power is:

1. (A) joule
2. (B) newton
3. (C) watt ✓
4. (D) second

4. The power of a water pump is 2 kW. The amount of water it can raise in one minute to a height of 5 metres is:

1. (A) 1000 litres
2. (B) 1200 litres
3. (C) 2000 litres
4. (D) 2400 litres ✓

5. A bullet of mass 0.05 kg has a speed of 300 m s⁻¹. Its kinetic energy will be:

1. (A) 2250 J ✓
2. (B) 4500 J
3. (C) 1500 J
4. (D) 1125 J

6. If a car doubles its speed, its kinetic energy will be:

1. (A) the same
2. (B) doubled
3. (C) increased to three times
4. (D) increased to four times ✓

7. The energy possessed by a body by virtue of its position is:

1. (A) kinetic energy
2. (B) potential energy ✓
3. (C) chemical energy
4. (D) solar energy

8. The magnitude of momentum of an object is doubled, the kinetic energy of the object will:

1. (A) double
2. (B) increase to four times ✓
3. (C) reduce to one-half
4. (D) remain the same

9. Which of the following is not renewable energy source?

1. (A) Hydroelectric energy
2. (B) Fossil fuels ✓
3. (C) Wind energy
4. (D) Solar energy

10. Work is said to be done when a force:

1. (A) acts on an object at rest
2. (B) is zero
3. (C) is balanced by another force without motion
4. (D) acts on an object and moves it through some distance ✓

11. Work is the product of the magnitude of force and the distance covered:

1. (A) in any direction
2. (B) in the direction of the force ✓
3. (C) perpendicular to the force
4. (D) opposite to the force

12. A man pushing hard on a wall does no work because:

1. (A) the force is zero
2. (B) the wall is heavy
3. (C) there is no friction
4. (D) there is no displacement ✓

13. Work done by a force acting at an angle θ with the direction of motion is:

1. (A) F S sin θ
2. (B) F S tan θ
3. (C) F S
4. (D) F S cos θ ✓

14. A person carrying a bag horizontally does zero work in the physics sense because the force on the bag is:

1. (A) zero always
2. (B) opposite to the displacement
3. (C) perpendicular to the displacement ✓
4. (D) along the displacement

15. Work is a:

1. (A) scalar quantity ✓
2. (B) vector quantity
3. (C) force
4. (D) type of power

16. The area under a force-distance graph represents:

1. (A) work done ✓
2. (B) power
3. (C) energy only
4. (D) momentum

17. The SI unit of work is:

1. (A) pascal
2. (B) joule ✓
3. (C) watt
4. (D) newton

18. One joule is equal to:

1. (A) 1 N m ✓
2. (B) 1 N s
3. (C) 1 W s⁻¹
4. (D) 1 kg m

19. One kilojoule is equal to:

1. (A) 10⁻³ J
2. (B) 10³ J ✓
3. (C) 10⁶ J
4. (D) 10² J

20. The work done by a force of 40 N moving a carton through 5 m in its own direction is:

1. (A) 45 J
2. (B) 35 J
3. (C) 200 J ✓
4. (D) 8 J