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在与九年义务教育初二物理教材配套的教师教学用书中,对测滑轮组机械效率实验中如何测动力作用点通过的距离作了如下建议:事先在细绳与动滑轮(或定滑轮)相切处做个带色的记号或打个结,再拉弹簧秤,量出这个结与动滑轮(或定滑轮)相切处的距离,就是细绳自由端通过的距离,我认为这个测法值得商榷。当绳子绕过滑轮组,最后一段(即弹簧秤拉
In the teacher’s teaching book matching the ninth-year compulsory education physics textbook, the following recommendations were made on how to measure the distance traveled by the action point in the mechanical efficiency test of the pulley block: the tangent to the string and the movable pulley (or the fixed pulley) in advance. Make a colored mark or tie a knot, and then pull the spring balance to measure the distance between the knot and the movable pulley (or the fixed pulley) at the tangent, which is the distance through which the free end of the string passes. I think this measurement is worth discussing. When the rope bypasses the pulley block, the last paragraph (ie, the spring balance pulls