MCAT Physics Question 24: Answer and Explanation

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Question: 24

9. Which of the following best characterizes the work–energy theorem?

  • A. The work done by any force is proportional only to the magnitude of that force.
  • B. The total work done on any object is equal to the change in kinetic energy for that object.
  • C. The work done on an object by any force is proportional to the change in kinetic energy for that object.
  • D. The work done by an applied force on an object is equal to the change in kinetic energy of that object.

Correct Answer: B

Explanation:

The work–energy theorem relates the total work done on an object by all forces to the change in kinetic energy experienced by the same object. While the work done by a force is indeed proportional to the magnitude of the force, it is also proportional to the displacement of the object, eliminating choice (A). The change in kinetic energy is equal—not proportional—to the total work done on the object; further, it is the net force, not any force, that relates to the work done on an object, eliminating choice (C). Finally, the change in kinetic energy of the object is equal to the work done by all of the forces acting on the object combined, not just the applied force, which eliminates choice (D).

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