题干

如图所示,在A处或B处的虚框内添加一个滑轮,利用三个滑轮组成滑轮组,要求使用时最省力.添加滑轮并完成滑轮组绕法.

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答案(点此获取答案解析)

解:由题:若在A处添加滑轮,是一个定滑轮,则滑轮组只有一个起滑轮,绕线后通过动滑轮绳子段数最多三段;

若在B处添加滑轮,是一个起滑轮,绕线后通过动滑轮绳子段数最多四段,更省力.

如图所示:

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