本题目来源于试卷: gc textbook chapter 8 Rotational Motion，类别为 通用国际物理
[问答题]
Why is it more difficult to do a sit-up with y 1yy:pw qy)gq,oud4czkjh.2)t v;y 2 cmrr hands behind your head than when your arms are stretched out in front of you? A diagram 4dm2;c z hvkr)2yc.jtmay help you to answer this.
参考答案: When you do a sit-up, torque from
your abdomen muscles must rotate the upper half of the body from a laying-down
position to a sitting-up position. The
larger the moment of inertia of the upper half of the body, the more torque is
needed, and thus the harder the sit-up is to do. With the hands behind the head, the moment of
inertia of the upper half of the body is larger than with the hands
outstretched in front.
本题详细解析:
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