来自《耶鲁大学开放课程：基础物理第8集第8集》

the velocity of the rocket at any instant,

可以求出任何时刻火箭的速度
if you knew the mass at that instant.

假如你知道那一瞬间的质量
The rocket will pick up speed and its mass will keep going down,

火箭逐渐加速质量逐渐减小
and the log of the mass before to the mass after

火箭的初质量与末质量的商的对数
times v0 is the change in the velocity of the rocket.

乘以 v0 就是火箭速度的变化量
Okay, so I have to give you some more ammunition

好的我要教给你更多知识
to do your homework problems;

让你能够解决作业中的问题
so, I'm going to discuss the last and final topic,

我将要介绍最后一个话题
which is the subject of collisions.

也就是碰撞
So, we're going to take the collision of two bodies,

我们考虑两个物体的碰撞
one body, another body, m1, v1, m2, v2,

一个物体另一个物体 m1 v1 m2 v2
they collide.

这两个物体碰撞