求解物理问题 ,常用的思维方法是根据问题给出的条件建立起物理模型 ,如果这个模型是一个完整的标准模型 ,则容易解决 .但有时由题给条件建立的模型不是一个完整的标准模型 ,比如说是模型A ,这时需要给原来的问题补充一些条件 ,由这些补充条件建立另一个容易求解的模型B ,并且? To solve physics problems, the common way of thinking is to establish a physical model based on the conditions given by the problem. If the model is a complete standard model, it is easy to solve. But sometimes the model created by the conditions given is not a complete standard model. For example, it is model A. At this time, we need to add some conditions to the original question. From these supplementary conditions, we can create another model B that is easy to solve.