Work and Energy MCQs for MDCAT Practice

Physics section, Work and Energy chapter. Up to eight free sample questions, each with the correct answer and a worked explanation. The full chapter opens in the app.

1. Question 1
   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:
   • A475 J (correct answer)
   • B450 J
   • C275 J
   • D250 J
   Correct answer: A

   This question tests the Work-Energy Theorem, where the change in kinetic energy equals the work done by the net force, considering a variable retarding force.
2. Question 2
   A parachutist is falling constant terminal velocity. Which statement is not correct?
   • AGravitational potential energy is converted into kinetic energy of the air.
   • BGravitational potential energy is converted into kinetic energy of the parachutist. (correct answer)
   • CGravitational potential energy is converted into thermal energy of the air
   • DGravitational potential energy is converted into thermal energy of the parachutist.
   Correct answer: B

   Constant velocity means no change in kinetic energy. This MCQ tests understanding of energy transformations during terminal velocity, focusing on work done by non-conservative forces.
3. Question 3
   A force F=(5i-3j)N is applied over a particle which displaces it from its origin to the point r=(2i-1j)m. The work done on the particle is:
   • A-7 joules
   • B+7 joules
   • C+ 13 joules (correct answer)
   • D-11 joules
   Correct answer: C

   Calculate work done by a constant force acting over a displacement using the dot product of the force and displacement vectors.
4. Question 4
   A motorist travelling at 10 ms-1 can bring his car to rest in a braking distance of 10 m. In what distance could he bring the car to rest from the period of 30 ms-1 using the same breaking force?
   • A17m
   • B30 m
   • C52 m
   • D90 m (correct answer)
   Correct answer: D

   This question tests the relationship between initial velocity, braking force, and stopping distance, highlighting the quadratic dependence of distance on velocity when force is constant.
5. Question 5
   If 10 kg mass is dropped from a certain height, hits the ground with speed 10 ms-1. The height will be
   • A100 m
   • B10 m
   • C50 m
   • D5 m (correct answer)
   Correct answer: D

   This question tests the application of the Work-Energy Theorem to find the height from which an object is dropped, given its final velocity.
6. Question 6
   The radius of the planet is five times the radius of earth but of same mass, value of g on the planet is
   • A5 g
   • B1/5 g
   • C1/20 g
   • D1/25 g (correct answer)
   Correct answer: D

   Gravitational acceleration depends inversely on the square of the radius for a constant mass, leading to a significantly reduced 'g' on a larger planet.
7. Question 7
   A neutron travel the distance of 12 m in a time interval of 3.6 x 10^(4) s. Assuming its speed was constant its kinetic energy is: (take 1.7 x 10^(-27) kg as the mass of neutron)
   • A3.1 eV
   • B4.7 eV
   • C6.91 eV
   • D5.78 eV (correct answer)
   Correct answer: D

   Calculate the kinetic energy of a neutron given its distance, time, and mass, converting the final answer to electron volts (eV).
8. Question 8
   Two bodies with kinetic energies having a ratio of 4:1, are moving with equal linear momentum. The ratio of their masses is:
   • A1:2
   • B1:4 (correct answer)
   • C4:1
   • D1:1
   Correct answer: B

   This question tests the relationship between kinetic energy, momentum, and mass when momentum is constant.

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