机械能守恒定律是力学中的一条重要定律.归纳一下,其表达方式主要有以下三种:(1)E_1=E_2.系统初状态的机械能E_1等于末状态的机械能E_2;(2)△E_p=△E_k.系统势能的减少量(或增加量)等于系统动能的增加量(或减少量);(3)△E_A=△E_B.把系统分为A、B两部分, The law of conservation of mechanical energy is an important law in mechanics. To sum up, there are mainly the following three expressions: (1) E_1=E_2. The mechanical energy E_1 in the initial state of the system is equal to the mechanical energy E_2 in the end state; (2) △E_p=△ E_k. The reduction (or increase) in the potential energy of the system is equal to the increase (or decrease) in the kinetic energy of the system; (3) △E_A = △E_B. The system is divided into two parts, A and B.