在学习动量守恒定律之后,会接触到多个物体参与作用的动量守恒问题.系统的动量守恒不是系统内所有物体的动量不变,而是系统内每个物体动量的矢量和不变.对于多个物体参与作用,要善于应用整体动量守恒;要善于选择合理系统;要善于选择相互作用过程. After learning the law of conservation of momentum, we will be exposed to the momentum conservation problem in which multiple objects participate. The momentum conservation of the system is not the constant momentum of all objects in the system, but the vector sum of the momentum of each object in the system. In order to participate in the role of an object, one must be good at applying overall momentum conservation; be good at choosing a reasonable system; be good at choosing an interaction process.