来自《耶鲁大学开放课程：基础物理第8集第8集》

So, let me summarize this last result.

让我总结出最后这个结论
In every collision,

在每个碰撞过程中
no matter what, momentum is conserved;

无论如何动量都是守恒的
the energy may or may not be.

而能量却不一定守恒
And if I give you a problem like this

如果我给你像这样的问题
where in between there's some funny business going on

其中有些有趣的地方
which is not energy conserving,

导致能量不守恒
don't use energy conservation from start to finish.

不要从头到尾都用能量守恒
Use momentum conservation,

用动量守恒
find the speed of the composite object.

找出整体的速度
This is what you've got to understand in your head.

这是你必须要理解的
It's not this equation.

而不是这个方程