Well, before, the speed is zero and so the momentum is zero. And there comes the bang and one piece flies in this direction with a certain velocity, v2 prime.

在之前，速度为，动量也为0，现在砰响了一声，一片朝这个方向飞，它的速度为v2。

youdao

And another piece flies off in this direction with mass m1, with velocity v1 prime.

另一片往这个方向飞，质量为m1，速度为v1。

youdao

And we're going to have q2 prime, and we're going to draw the arrows in the positive direction in these cases.

还有q 2一撇，在这个例子中，我们把箭头朝正方向。

youdao

And we're going to have q2 prime, and we're going to draw the arrows in the positive direction in these cases.

还有q2一撇，在这个例子中,我们把箭头朝正方向。

麻省理工公开课 - 热力学与动力学课程节选

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