参考答案:
The power needed to lift the suitcase is the work required to lift the suitcase, divided by the time that it takes.
(a) Since work does NOT depend on the path, the power will not depend on the path either,
assuming the time is the same for all paths.
(b) The power DOES depend on the time taken. The more time taken, the lower the power needed.
(c) The power needed DOES depend on the height of the table. A higher table requires more work to lift the suitcase. If we assume that the time to lift the suitcase is the same in both cases, then to lift to the higher table takes more power.
(d) The power DOES depend on the weight of the suitcase. A heavier suitcase requires more force to lift, and so requires more work. Thus the heavier the suitcase, the more power is needed to lift it (in the same amount of time).
本题详细解析:
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