Free Work and Energy MCQs with Answers
748 Work and Energy MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Work transfers energy when a force causes displacement, while kinetic energy, gravitational potential energy and power describe motion, position and the rate of energy transfer. The work-energy theorem links net work with change in kinetic energy, and efficiency accounts for energy losses rather than treating them as energy destruction.
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- A. 0 degrees
- B. 45 degrees
- C. 90 degrees
- D. 180 degrees
Explanation: Work is the scalar product Fd cos theta, and cos 90 degrees is zero, so a force perpendicular to the displacement does no work.
Correct answer: 90 degrees- A. equal to mgh
- B. zero
- C. equal to the weight times the distance walked
- D. negative
Explanation: The upward force supporting the suitcase is perpendicular to the horizontal displacement, so the work done against gravity is zero.
Correct answer: zero- A. mass is halved
- B. speed is doubled
- C. speed is increased by a factor of the square root of two
- D. mass is doubled and speed halved
Explanation: Kinetic energy is half m v squared, so it scales with the square of the speed.
Correct answer: speed is increased by a factor of the square root of two- A. 10 J
- B. 20 J
- C. 40 J
- D. 80 J
Explanation: Kinetic energy is half times 5 times 4 squared, which is half times 5 times 16, giving 40 J.
Correct answer: 40 J- A. its total mechanical energy
- B. the change in its kinetic energy
- C. the change in its potential energy
- D. its momentum
Explanation: The work-energy theorem equates net work with the change in kinetic energy, which is why a braking force doing negative work brings a car…
Correct answer: the change in its kinetic energy- A. the total work done
- B. the rate of doing work
- C. work done times time taken
- D. force times displacement
Explanation: Power is work done per unit time, measured in watts, where one watt is one joule per second.
Correct answer: the rate of doing work- A. 100 W
- B. 1000 W
- C. 2000 W
- D. 20000 W
Explanation: The work done is mgh, which is 200 times 10 times 10, giving 20000 J. Dividing by the 20 s taken gives 1000 W, or 1 kW.
Correct answer: 1000 W- A. total mechanical energy increases
- B. potential energy converts into kinetic energy with the total unchanged
- C. kinetic energy converts into potential energy
- D. total mechanical energy decreases
Explanation: Gravity is a conservative force, so in the absence of air resistance the sum of kinetic and potential energy stays constant while…
Correct answer: potential energy converts into kinetic energy with the total unchanged- A. 30%
- B. 43%
- C. 70%
- D. 143%
Explanation: Efficiency is useful output divided by total input times 100, which is 350 over 500 times 100, giving 70%.
Correct answer: 70%- A. 10 J
- B. 25 J
- C. 100 J
- D. 1000 J
Explanation: Potential energy gained is mgh, which is 2 times 10 times 5, giving 100 J.
Correct answer: 100 J- A. a force acts on it
- B. a force acts and the body moves with a component of displacement along the force
- C. the body is at rest
- D. the body has energy
Explanation: Work is the dot product of force and displacement, so a porter standing still holding a heavy suitcase does no work on it however tiring…
Correct answer: a force acts and the body moves with a component of displacement along the force12. A force of 50 N pulls a box 4 m along the floor at 60 degrees to the horizontal. The work done is
- A. 200 J
- B. 100 J
- C. 173 J
- D. 0 J
Explanation: Only the component of force along the displacement counts, so the work is 50 multiplied by 4 multiplied by cos 60, which is 200 multiplied…
Correct answer: 100 J- A. maximum
- B. zero
- C. equal to the kinetic energy
- D. negative
Explanation: The force points to the centre while the displacement is along the tangent, so the two are perpendicular and the dot product is zero at…
Correct answer: zero- A. mv
- B. half mv squared
- C. mv squared
- D. half mv
Explanation: Because the speed is squared, doubling it quadruples the kinetic energy, which is why stopping distances grow so sharply with speed.
Correct answer: half mv squared- A. double
- B. four times
- C. half
- D. unchanged
Explanation: Kinetic energy depends on the square of the speed, so a factor of two in speed gives a factor of four in energy, and the braking distance…
Correct answer: four times- A. mgh
- B. half mgh
- C. mg divided by h
- D. mh
Explanation: The work done against a constant weight mg over a height h is mgh, and only the vertical height matters, not the path taken.
Correct answer: mgh- A. 10 J
- B. 50 J
- C. 100 J
- D. 25 J
Explanation: Using mgh, the energy is 2 multiplied by 10 multiplied by 5, giving 100 J.
Correct answer: 100 J- A. the square root of 2gh
- B. 2gh
- C. gh
- D. the square root of gh
Explanation: Equating the potential energy mgh to the kinetic energy half mv squared cancels the mass and gives v as the square root of 2gh, which is…
Correct answer: the square root of 2gh- A. the total work done
- B. the rate at which work is done or energy is transferred
- C. the force multiplied by the distance
- D. the energy stored in a body
Explanation: One watt is one joule per second, so power tells you how quickly energy is delivered rather than how much.
Correct answer: the rate at which work is done or energy is transferred- A. 500 W
- B. 1000 W
- C. 200 W
- D. 10000 W
Explanation: The work done is mgh, that is 100 multiplied by 10 multiplied by 10, giving 10,000 J, and dividing by 20 seconds gives 500 W.
Correct answer: 500 WWork and Energy MCQs: common questions
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