MCAT Physics Question 29: Answer and Explanation
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Question: 29
14. If the gravitational potential energy of an object has doubled in the absence of nonconservative forces, which of the following must be true, assuming the total mechanical energy of the object is constant?
- A. The object has been lifted to twice its initial height.
- B. The kinetic energy of the object has been halved.
- C. The kinetic energy has decreased by the same quantity as the potential energy has increased.
- D. The mass of the object has doubled.
Correct Answer: C
Explanation:
In the absence of nonconservative forces, all changes potential energy must be met by an equal change in kinetic energy. Note that it is the difference in potential energy that is the same as the difference in kinetic energy, not the proportionality, eliminating choice (B). Both choices (A) and (D) could be true statements but do not necessarily have to be—the object's mass could have been quadrupled while its height was halved.