AP Physics 1 Question 320: Answer and Explanation
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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
In all of these cases, mechanical energy must be conserved. Thus, the energy required will be mgh for all of them.