In this chapter we develop the implication's of momentum conservation in the motion of a collection of particles . 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。
The bland sameness of space is at the root of both momentum conservation and angular-momentum conservation . 平淡无奇的空间一致性，既是动量守恒的根本，又是角动量守恒的根本。
We shall see next how two similar concepts, those of impulse and momentum, also arise from these laws . 下面我们将看到两个相似的概念，即冲量和动量，也是从这些定律引伸出来的。
The relativistic mechanics in chapter 21 is circumscribed with primary emphasis on the concepts of energy and momentum . 第二十一章的相对论性力学主要限于强调能量和动量的概念。
The principle of conservation of momentum holds whatever the nature of the internal forces, conservative or not . 动量守恒原理则不管内力的性质如何（保守的或非保守的）都能适用。
In other words, the vertical component of its linear momentum remains zero, since there is no resultant vertical force . 换句话说，因为没有竖直方向的合力，所以线动量的竖直方向仍为零。
It is important to realize that momentum conservation applies even to inelastic collisions, in which the kinetic energy is not conserved . 必须记住，动量守恒甚至对于非弹性碰撞也是成立的，尽管这时动能已不守恒。
The sledge gained momentum as it ran down the hill 雪橇从山上下冲时动量越来越大
The sledge gained momentum as it run down the hill 雪橇从山上下冲时动量越来越大。
