虽然初中教材上明确说定滑轮不能省力,但有些教师从一些特殊例子出发,分析出定滑轮能省力.1特例分析认为定滑轮能省力的称为A方,也有少数反对这一观点的,称为B方.例1.如图1,吊篮重60N,人重800N,每个滑轮重20N,忽略绳重和摩擦力,要吊篮静止不动人需要的拉力F是多大?分析:人的拉力F与动滑轮右侧绳 Although the junior high school teaching materials expressly states that the pulleys can not save energy, some teachers start from a few special examples to analyze how the pulleys can save effort.1 The special case analysis shows that the fixed pulleys can be economically called A-side and a few objections to this view. For the B side Example 1. As shown in Figure 1, the basket weighs 60N, weight 800N, each pulley weighs 20N, ignoring the rope weight and friction, to pull the basket still unmovable tension F is much? Analysis: Human Rally F and moving pulley right rope