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一、整体分析,选定对象机械能守恒定律适用于只有重力做功或系统内弹簧弹力做功的各种情况。遇到这类问题时,先要从物体或系统的整体受力情况出发,选取恰当的研究对象,适当忽略其他受力情况。例如,如果只有重力做功,可以选取一个物体或几个物体作为研究对象,也可以把这几个物体构成的系统作为研究对象。例1如图1,光滑水平面上有一质量为M的小车,一条长绳(绳子长度大于桌面长度)一头连接小车,另一头通过光滑滑轮与一个质量为m
First, the overall analysis, the selected object The law of conservation of mechanical energy is applied to all kinds of situations where the work of gravity alone or the spring elasticity of the system does work. Encountered such problems, we must first object or system from the overall stress situation, select the appropriate research object, due to ignore other stress situations. For example, if only gravity works, one or several objects may be selected as the object of study, and the system of these objects may also be taken as the object of study. Example 1 As shown in Figure 1, there is a car with a mass M on a smooth water level. A long rope (the length of the rope is greater than the length of the tabletop) is connected to the car one by one and the smooth pulley is connected with a mass m