本题目来源于试卷: 美国2021年物理杯赛真题 PHYSICS BOWL 2021，类别为 美国物理杯赛(Physics Bowl)
[单选题]
Two cranes are used to lift loads vertically at constant speed from the ground to the top of a building. Crane 1 lifts an 8000-N load a height of 40 m in a time of 20 minutes. Crane 2 lifts a6400-N load a height of 50 m in a time of 16 minutes. Which statement below correctly compares the mechanical power output of each crane?
A. The cranes have the same power because they perform the same amount of work.
B. The cranes have the same power because the ratio of force exerted to time is the same.
C. Crane 1 has a greater power because it exerts more force to lift the load.
D. Crane 1 has a greater power because it raises the load over a longer time.
E. Crane 2 has a greater power because it performs the same amount of work in less time.
参考答案: E
本题详细解析:
$p=\frac{w}{t} =\frac{f∆x}{t}$ . Both Cranes do 320.000 J of work. Crane 2 does it in less time.
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