碰撞时质点系动量的改变等于作用在质点系上所有外碰撞冲量的矢量和。
The change in the momentum of a system of particles during an impact is equal to the vector sum of all the external impulses acting on the system.
采用简捷的方法推导质点系相对于任意动点的动量矩定理，并由此引出质点系相对于质心的动量矩定理和质点系相对于速度瞬心的动量矩定理。
There from it is used to obtain the principles of the angular of momentum of the system of particles with respect to its cenier of mass and instantaneous center of velocity.
在本章中，我们要揭示一个质点集体作运动时动量守恒的含义。
In this chapter we develop the implication's of momentum conservation in the motion of a collection of particles.
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