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1·R One is the position vector, r.

一边是位矢。

2·And, we look at how the position vector changes.

来看看位置矢量的改变。

3·So, it's the second derivative of a position vector.

它是位置向量的二阶导。

4·Well, I claim that the position vector is in the plane.

我断言，这个位置矢量在平面上。

5·And this, now, is the position vector of the center of mass.

现在，这里是，物体的矢量中心。

6·So, we want to decompose the position vector into a sum of simpler vectors.

故我们是把位置向量，分解为简单向量的和。

7·We have the cross-product of the position vector to this point times the force.

我们用这个点的，位置向量，乘以这个力。

8·Or, maybe I should insteadthink of it in terms of a position vector if it helps you.

也许我应该用位置矢量来考虑,如果你们觉得有帮助的话。

9·So, the velocity vector is the derivative of a position vector with respect to time.

速度向量，是位置向量关于时间的导数。

10·Well, it might be good to think of, maybe, the position vector, and maybe its variation.

这还是比较容易想到的，假如这是位置矢量，这是它的变化量。