碰撞时由于作用时间短,内力远大于外力,因而碰撞问题符合动量守恒.在碰撞问题中,除弹性碰撞外动能都不守恒,特别是完全非弹性碰撞其动能损失最多.动能损失是指碰撞前的总动能与碰撞后的总动能之差.若完全非弹性碰撞中两个物体的质量分别用m1、m2表示,碰撞前的速度分别用v1、v2表示,发生完全非弹性碰撞后的速度用v表示,则动量守恒表达式为 Because of the short action time during the collision, the internal force is much larger than the external force, so the collision problem is in accordance with the conservation of momentum. In the collision problem, kinetic energy is not conserved except for the elastic collision, especially the fully inelastic collision has the largest kinetic energy loss. Kinetic energy loss means before collision. The difference between the total kinetic energy of the vehicle and the total kinetic energy after the collision. If the masses of the two objects in the fully inelastic collision are respectively represented by m1 and m2, the velocity before the collision is represented by v1 and v2 respectively, and the velocity after the completely inelastic collision occurs. v means that the momentum conservation expression is