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:
Answer:
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?
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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:
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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?
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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:
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Explanation:
When force and displacement are in opposite directions, the work done is negative.
6. A machine that is 100% efficient:
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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:
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Explanation:
A stretched bow stores elastic potential energy.
8. The capability of doing work is defined as:
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Explanation:
Energy is the capability of doing work.
9. The work done against friction is:
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Explanation:
The work done against friction primarily results in the generation of heat.
10. Power is defined as:
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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:
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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?
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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:
Answer:
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:
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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:
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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):
Answer:
Explanation:
Work = mgh = 100 x 10 x 10 = 10000 J.
17. A body freely falling from a height has:
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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:
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Explanation:
Power = Work/Time = 5000/10 = 500 W.
19. Work and energy have the same SI units. What is it?
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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:
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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:
Answer:
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:
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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?
Answer:
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:
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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:
Answer:
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.