AP Physics 1 Question 320: Answer and Explanation

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Question: 320

8. The diagrams above show a box of mass m being lifted from the ground up to a height of h via three different methods. In situation A, the box is simply lifted by a person. In B, it is pushed up a ramp with an incline angle of 30 degrees. In C, it is lifted by a pulley system. Assuming ideal conditions (no friction) for all of these situations, which of the following correctly ranks the amount of work required to lift the box in each case?

  • A. A > B > C
  • B. A > B = C
  • C. C > B > A
  • D. A = B = C

Correct Answer: D

Explanation:

D

In all of these cases, mechanical energy must be conserved. Thus, the energy required will be mgh for all of them.