所谓守恒,可理解为某一物理量在满足条件的前提下,在物理变化的过程中保持不变.守恒定律是贯穿整个物理学中一条最重要最基本的规律.运用守恒定律去解题,不需考虑系统内部相互作用的具体细节,使问题简化. The so-called conservation can be understood as that a certain physical quantity remains unchanged in the process of physical change under the premise of satisfying the condition. The law of conservation is the most important and most basic rule throughout the whole physics. The conservation law is used to solve the problem. The specific details of the interaction within the system need to be considered to simplify the problem.