对滑轮组的省力情况:在常规的方法下使用,同学们容易判断出拉力的大小;若将滑轮组使用方法稍加变动,就常常发现有的同学无从下手,有的判断错误.究其原因,一是受思维定势影响,二是不会进行受力分析.此时,若能引导学生采用等效的方法,变换角度,把滑轮组转变成常规情况下来分析,问题就迎刃而解了.例1如图1中,两个物体重分别为G1和G2,忽略滑轮重和摩擦,当滑轮平衡时,G1与G2之比是多少? Savings on the pulleys: In the conventional method, the students can easily determine the size of the pull force. If the method of use of the pulleys is changed slightly, it is often found that some students cannot start, and some make mistakes. The reason is as follows: It is influenced by the mindset, and the second is that no force analysis will be performed. At this time, if we can guide students to adopt an equivalent method, change the angle, and turn the pulley block into routine analysis, the problem will be solved. Example 1 In the 1st, the weights of the two objects are G1 and G2, respectively, regardless of the weight of the pulley and friction. When the pulley is balanced, what is the ratio of G1 to G2?