Physics: Work, Energy, and Power Class 11 MCQ

Understanding the concepts of work, energy, and power is fundamental in the field of physics. These interrelated ideas form the basis of many complex systems and applications. To help you gauge your understanding, we present 25 MCQs on this topic.

1. Work is considered positive when:

a) The force and displacement are in the same direction
b) The force and displacement are in opposite directions
c) There is no force applied
d) There is no displacement

Answer:

a) The force and displacement are in the same direction

Explanation:

Work is positive when the force causing the displacement acts in the same direction as the displacement.

2. What is the SI unit of power?

a) Joule
b) Newton
c) Watt
d) Pascal

Answer:

c) Watt

Explanation:

Power is defined as the rate of doing work, and its SI unit is Watt.

3. If a body is moving with constant velocity, its kinetic energy:

a) Increases
b) Decreases
c) Remains constant
d) Becomes zero

Answer:

c) Remains constant

Explanation:

Kinetic energy depends on the velocity squared, so if velocity is constant, kinetic energy remains constant.

4. Which energy is associated with an object due to its position?

a) Kinetic energy
b) Potential energy
c) Thermal energy
d) Nuclear energy

Answer:

b) Potential energy

Explanation:

Potential energy is the energy possessed by a body due to its position or configuration.

5. Work done on an object is negative when:

a) The object moves in the direction of the force
b) The object does not move
c) The object moves opposite to the direction of the force
d) The object’s speed increases

Answer:

c) The object moves opposite to the direction of the force

Explanation:

When force and displacement are in opposite directions, the work done is negative.

6. A machine that is 100% efficient:

a) Doesn’t exist due to energy losses like friction
b) Converts all input energy to output energy without any losses
c) Has a mechanical advantage of zero
d) Consumes no energy

Answer:

b) Converts all input energy to output energy without any losses

Explanation:

100% efficiency means there are no energy losses, and all input energy is converted to useful output.

7. The energy stored in a stretched bow is:

a) Kinetic energy
b) Mechanical energy
c) Potential energy
d) Thermal energy

Answer:

c) Potential energy

Explanation:

A stretched bow stores elastic potential energy.

8. The capability of doing work is defined as:

a) Force
b) Momentum
c) Power
d) Energy

Answer:

d) Energy

Explanation:

Energy is the capability of doing work.

9. The work done against friction is:

a) Converted to potential energy
b) Used in doing useful work
c) Converted to kinetic energy
d) Converted to heat

Answer:

d) Converted to heat

Explanation:

The work done against friction primarily results in the generation of heat.

10. Power is defined as:

a) Work x Time
b) Work / Distance
c) Work / Time
d) Force x Distance

Answer:

c) Work / Time

Explanation:

Power measures the rate of doing work, which is work done per unit time.

11. The gravitational potential energy of an object is always:

a) Negative
b) Positive
c) Zero
d) Equal to its kinetic energy

Answer:

b) Positive

Explanation:

Gravitational potential energy is positive as it is measured from a reference point, usually the ground, and is based on height and mass.

12. Which of the following is a scalar quantity?

a) Force
b) Velocity
c) Displacement
d) Work

Answer:

d) Work

Explanation:

Work is a scalar quantity as it has magnitude but no specific direction.

13. If the displacement of an object is zero, the work done on it is:

a) Zero
b) Maximum
c) Positive
d) Negative

Answer:

a) Zero

Explanation:

Work is the product of force and displacement. If either is zero, the work done is zero.

14. The rate of change of work is called:

a) Energy
b) Momentum
c) Force
d) Power

Answer:

d) Power

Explanation:

Power is defined as the rate at which work is done or the rate of change of work.

15. A car moving with a velocity of 30 m/s is stopped by brakes. The kinetic energy of the car is:

a) Converted to potential energy
b) Converted to thermal energy
c) Transferred to the road
d) Stored in the brakes

Answer:

b) Converted to thermal energy

Explanation:

When brakes are applied to stop the car, the kinetic energy is mostly converted to heat due to friction.

16. The work done in lifting a 100 kg weight to a height of 10 m is (g=10 m/s^2):

a) 1000 J
b) 5000 J
c) 10000 J
d) 20000 J

Answer:

c) 10000 J

Explanation:

Work = mgh = 100 x 10 x 10 = 10000 J.

17. A body freely falling from a height has:

a) Only potential energy at the start
b) Only kinetic energy at the end
c) Equal potential and kinetic energy while falling
d) Zero total energy throughout

Answer:

a) Only potential energy at the start

Explanation:

At the start, when the body is at rest at a certain height, it has only potential energy.

18. If an engine does 5000 J of work in 10 seconds, its power output is:

a) 50 W
b) 500 W
c) 5000 W
d) 0.5 W

Answer:

b) 500 W

Explanation:

Power = Work/Time = 5000/10 = 500 W.

19. Work and energy have the same SI units. What is it?

a) Newton
b) Pascal
c) Joule
d) Watt

Answer:

c) Joule

Explanation:

Both work and energy represent the same physical concept and thus have the same SI unit, which is Joule.

20. A freely falling object possesses:

a) Only kinetic energy
b) Only potential energy
c) Both kinetic and potential energy
d) Neither kinetic nor potential energy

Answer:

c) Both kinetic and potential energy

Explanation:

As the object falls, its height (and thus potential energy) decreases, while its velocity (and thus kinetic energy) increases.

21. If the net work done on an object is zero, its kinetic energy:

a) Increases
b) Decreases
c) Remains unchanged
d) Becomes zero

Answer:

c) Remains unchanged

Explanation:

According to the work-energy theorem, if the net work done on an object is zero, there is no change in its kinetic energy.

22. The capability to do work is defined as:

a) Force
b) Momentum
c) Energy
d) Power

Answer:

c) Energy

Explanation:

Energy is the capacity to do work. If an object possesses energy, it has the ability to exert a force and cause a displacement.

23. Which energy principle is responsible for conservation of mechanical energy in a pendulum?

a) Conservation of potential energy
b) Conservation of kinetic energy
c) Conservation of total energy
d) None of the above

Answer:

c) Conservation of total energy

Explanation:

In a pendulum, the total mechanical energy (potential + kinetic) remains conserved as long as no non-conservative forces (like air resistance) act on it.

24. An object of mass m, moving with velocity v, has a kinetic energy of:

a) 1/2 mv^2
b) mv^2
c) mv
d) m^2v

Answer:

a) 1/2 mv^2

Explanation:

The kinetic energy (K.E) of an object of mass m, moving with a velocity v, is given by K.E = 1/2 mv^2.

25. When a spring is compressed, its potential energy:

a) Decreases
b) Increases
c) Remains constant
d) Becomes zero

Answer:

b) Increases

Explanation:

When a spring is compressed or stretched, it stores energy. This energy is in the form of potential energy which increases as the compression or stretch increases.

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top