You can actually take derivatives of a vector with time.

你可以直接求位矢对时间的导数

耶鲁公开课 - 基础物理课程节选

More position vectors? I want to look at that.

例如其它的位矢,我想来看一下

耶鲁公开课 - 基础物理课程节选

When you vary time a little bit and ask, "How does R change?"

当你把时间改变一个微元,然后问,"位矢 R 会怎样变化"

耶鲁公开课 - 基础物理课程节选

We've got one vector which is R.

我们已有的一个矢量,位矢 R

耶鲁公开课 - 基础物理课程节选