机械能守恒定律是物理学中的常用规律,应用机械能守恒定律解题时,一定要注意守恒条件的判断．而判断机械能是否守恒有两个途径．一是从做功的角度,看是否只有重力或弹簧的弹力做功．二是从能量转化的角度,看是否有摩擦和介质阻力,看是否有机械能转化为内能,看系统与其他物体之间是否有能量 The law of conservation of mechanical energy is a common law in physics. When applying the law of conservation of mechanical energy to solve problems, we must pay attention to the judgment of conservative conditions. There are two ways to determine whether mechanical energy is conserved. First, from the perspective of doing work, see if there is only gravity or spring elasticity. The second is from the perspective of energy conversion, to see if there is friction and medium resistance, to see if there is mechanical energy converted to internal energy, to see if there is energy between the system and other objects