有了旋转的角动量。
Look at that spin angular momentum.
观察那个旋转角动量。
Angular momentum is in this direction.
角动量是这个方向了。
Angular momentum is now in this direction.
角动量现在是在这个方向。
We have here the spin angular momentum that you saw.
这有一个旋转的角动量,如你们所见。
I add angular momentum in this direction and you see that here.
我在这个方向加入了角动量，你们可以在这看到。
And so the angular momentum of spin of the wheel is in this direction.
所以旋转的角动量是，这个方向。
But notice that l, the spin angular momentum, has moved from here to here.
注意l，旋转的角动量，已经从这移到了这。
Therefore there is a total angular momentum which is the vectorial sum of the two.
因此，总的角动量,有两个向量。
Therefore there is a total angular momentum which is the vectorial sum of the two.
因此，总的角动量,有两个向量。
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