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答案:1 悬赏:30 手机版

解决时间 2021-05-22 21:38

提问者网友：树红树绿
2021-05-22 10:19

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Suppose Michael Phelps,winner of 14 Olympic gold medals,uses mostly arm
motion to pull himself along,exerting an average force of 260 N through a distance of 1.8 m in
each stroke.(See figure below.) Assuming he does 110 strokes per minute,(a) calculate the
work done in each stroke,and (b) calculate the useful power generated by his arm.

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最佳答案

五星知识达人网友：夜余生
2021-05-22 11:02

(a) Assuming that each stroke is a perfect half circle,the distance of each stroke is L=½πD=0.5x3.14x1.8=2.83 m.
Therefore,the work done in each stroke is F x L=260N x 2.83m=734.8 J.
(b) In each stroke,the upward and downward force is not useful in pulling him along.
The useful work done in each stroke is F x D=260N x 1.8m=468 J.
Time of each stroke 60/110=0.545 s.
Therefore,the useful power is 468 / 0.545 = 858.0 W.

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