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Free Work-Energy Theorem MCQs with Answers

26 Work-Energy Theorem MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

The work-energy theorem states that the net work done on an object equals its change in kinetic energy. Questions involve positive and negative work, variable forces and force-displacement graphs, acceleration or deceleration, and the difference between this theorem and conservation of mechanical energy, which also requires attention to potential energy and non-conservative work.

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26 questions · page 1 of 2

1. The work-energy theorem states that the net work done on a body equals

  • 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…

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Correct answer: the change in its kinetic energy

2. For a body sliding down a frictionless slope, the speed at the bottom depends on

  • A. the length of the slope
  • B. the vertical height dropped, but not on the angle of the slope
  • C. the mass of the body
  • D. the angle only

Explanation: Energy conservation gives half mv squared equal to mgh, so the mass cancels and only the height matters, which means a gentle ramp and a…

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Correct answer: the vertical height dropped, but not on the angle of the slope

3. The law of conservation of energy states that energy

Fairly easy
  • A. can be created when needed
  • B. can be destroyed by friction
  • C. can be transformed from one form to another but the total remains constant
  • D. always increases in an isolated system

Explanation: Friction does not destroy energy; it converts organised kinetic energy into disordered thermal energy, which is harder to use but is still…

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Correct answer: can be transformed from one form to another but the total remains constant

4. A ball of mass 0.2 kg is thrown vertically upwards by applying a force by hand. If the hand moves 0.2 m while applying the force and the ball goes up to 2 in height further, find the magnitude of the force. Consider g = 10m/s 2

  • A. 22N
  • B. 16N
  • C. 20N
  • D. 4N

Explanation: The hand does work equal to the ball's gain in gravitational potential energy while it moves 0.2 m and then rises a further 2.0 m: F x 0.2…

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Correct answer: 22N

5. The purpose of flywheel in the engines is________________?

  • A. to smooth out the energy variation
  • B. to add more weight to engine to work it stable
  • C. to start engine
  • D. both A and BEngine & Transmission

Explanation: A flywheel stores rotational kinetic energy when the engine produces excess torque and releases it when torque falls, smoothing energy and…

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Correct answer: to smooth out the energy variation

6. Which equation is not dimensionally correct ?

  • A. E=mc2
  • B. Vf=Vi+at
  • C. S=Vt2
  • D. S=1/2at2

Explanation: In S = Vt², the right side has dimensions (m s^-1)(s²) = m s, which is not a length.

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Correct answer: S=Vt2

7. Dimensional analysis is helpful for__________________?

  • A. Deriving a possible formula
  • B. Checking the homogeneity of a physical equation
  • C. Verification of laws
  • D. Only A and B are correct

Explanation: Dimensional analysis can suggest a possible formula and can test whether both sides of an equation have the same dimensions.

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Correct answer: Only A and B are correct

8. The ration stress to strain in youngs modulus of the material then tension is__________________?

  • A. Directly proportional to extension
  • B. Directly proportional to strain
  • C. Directly proportional to square of amplitude
  • D. Inversely proportional to extension

Explanation: Within the elastic limit, Young's modulus remains constant, so stress is proportional to strain.

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Correct answer: Directly proportional to extension

9. A ball of mass m is dropped from a certain height h on a sand floor. If the ball penetrates 'x' meters into the sand, the average resistive force offered by sand on the ball is:

  • A. mg (x/h)
  • B. mg (h/x)
  • C. mg (1+h/x)
  • D. mg (1 - h/x)
  • E. mgh + mgd

Explanation: The work done by the resistive force of sand is given by:W = Fd = (1/2) kx2where F is the average resistive force offered by the sand on…

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Correct answer: mg (h/x)

10. A bullet penetrating 30cm into its target loses its velocity by 50%. What additional distance will it penetrate into the target before it comes to rest?

  • A. 30 cm
  • B. 20 cm
  • C. 10 cm
  • D. 5 cm

Explanation: Let's use the equation of motion to find the additional distance the bullet will penetrate before coming to rest.

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Correct answer: 10 cm

11. A bullet of mass 10 g leaves a rifle at an initial velocity of 1000 m/s and strikes earth at the same level with a velocity of 500 m/s. The work done in overcoming the resistance of air will be:

  • A. 500 J
  • B. 5000 J
  • C. 3750 J
  • D. 475 J

Explanation: Work done against friction = Loss in Kinetic EnergyLoss in Kinetic Energy (ΔKE) = 1/2 x m (u2 - v2)Where 'u' is the initial velocity and…

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Correct answer: 3750 J

12. A loaded and an unloaded cart are moving with same kinetic energies such that same retarding force acts on them and they finally stop after covering "S1" and "S2" distances respectively, which of the following is true?

  • A. S1=S2
  • B. S1<S2
  • C. S1>S2
  • D. None of these

Explanation: According to Work-Energy PrincipleChange in K.E= W frictionChange in K.E = FdcosStopping distance = dSince both cars have same K.E, so…

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Correct answer: S1=S2

13. Work done on a body equals change in its _ energy.

  • A. Total
  • B. Potential
  • C. Kinetic
  • D. All of these

Explanation: Since the type of work that is being done isn't specified, a body can have either kinetic energy due to motion or potential energy due to…

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Correct answer: All of these

14. If mass 'm' is dropped from height 'h' vertically, 'f' is the force of friction during downward motion and 'v' is the velocity at bottom, following will hold:

  • A. ½mv²=mgh+fh
  • B. mgh=½mv²-fh
  • C. fh=mgh+½mv²
  • D. mgh=½mv²+fh

Explanation: Throughout the course of this fall, we would be having the gravitational potential energy converted to kinetic energy and the energy…

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Correct answer: mgh=½mv²+fh

15. The work energy theorem states that the net work done on a body equals

  • A. its total energy
  • B. the change in its kinetic energy
  • C. the change in its potential energy
  • D. the power delivered to it

Explanation: Positive net work speeds the body up and negative net work, as from friction, slows it down, and the theorem holds whatever forces are…

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Correct answer: the change in its kinetic energy

16. When work done by force of gravity is negative (only gravity is acting)

  • A. KE decreases
  • B. PE increases
  • C. Both (A) and (B)
  • D. None of these

Explanation: If the work done by gravity is negative, it means that the gravitational force is acting in the direction opposite to the direction of…

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Correct answer: Both (A) and (B)

17. A block of mass 10 kg is moving in x-direction with a constant speed of 10 m/s. It is subjected to a retarding force F = -0.1 J/m during its travel from x = 20 m to x = 30 m. Its final kinetic energy will be:

  • A. 475 J
  • B. 450 J
  • C. 275 J
  • D. 250 J

Explanation: m=10kgv=10m/sFret=-0.1J/mAt x= 20mF= -0.1 (20)=2NAt x=30mF=-0.1 (30)=3NAverage force=2+3/2 = 5/2 = 2.5NSo the average work done by the…

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Correct answer: 475 J

18. The work done by the push of air on an object of mass 10 kg falling from rest through a vertical distance of 10 m is 500 J. Find the velocity of the object at the end of 10 m fall: {g = 10 m/s2).

  • A. 20 m/sec
  • B. 12 m/sec
  • C. 5 m/sec
  • D. 10 m/s

Explanation: Given that, mass = 10kg. Vertical distance = 10m. Since starting from rest Initial velocity = 0 m/s. Work done = 500J.

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Correct answer: 10 m/s

19. A bullet of mass 10g leaves a rifle at an initial velocity 1000 m/s and strikes earth at the same level with a velocity of 500 m/s. The work in overcoming the resistance of air will be:

  • A. 500 J
  • B. 5000 J
  • C. 3750 J
  • D. 475 J

Explanation: work energy theorem Work done in overcoming the air resistance=Loss in energyInitial KE = 0.5x m x v1^2 = 0.5 x 0.01 x 10^6 = 5000 J Final…

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Correct answer: 3750 J

20. When total work done on a particle is positive then_.

  • A. KE remain constant
  • B. Momentum increases
  • C. KE decreases
  • D. All of these

Explanation: If work done is positive then kinetic energy increases. Since kinetic energy is directly proportional to the momentum therefore momentum…

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Correct answer: Momentum increases
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Work-Energy Theorem MCQs: common questions

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