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滑轮组的机械效率是初中物理知识的重点、难点,题型主要是实验题和计算题.这部分知识的涉及面广,综合性强,看似复杂多变,实则可根据使用滑轮组的目的将之分为三种类型.一、克服物体所受的重力做功用滑轮组竖直拉动重物时,使用滑轮组的目的是提供一个与重力平衡的拉力,从而将重物提升一定高度,此时克服重力做的功为有用功,即W_有=Gh;绳子自由端拉力做的功为总功,即W_总=Fs.生活、生产中绝大部分情况都是利用滑轮组将重物提升一定高度
The mechanical efficiency of the pulley block is the focus of junior physics knowledge, the difficulties, the questions are mainly experimental questions and computational questions.This part of knowledge involves a wide range, comprehensive, seemingly complex and changeable, but according to the purpose of using pulley group Divided into three types.One, to overcome the gravity of the object to do the work Pulley group vertical pulling heavy objects, the purpose of the use of pulley block is to provide a balance of gravity and the tension, which will lift a certain height, this time to overcome the gravity Of the work is useful work, that W_ = Gh; rope free end pull force to do the total work, that W_ total = Fs. Life, most of the production is the use of pulley group will lift a certain height