And, the way we can get it, so, it's called usually V, so, V here stands for velocity more than for vector. And, you just get it by taking the derivative of a position vector with respect to time.

根据它的原理，我们通常用v表示,这里的V更代表速率而不是矢量，你能通过,对一个关于时间的位置向量求导得到它。

youdao

Also that velocity, v, in that equation number five will also change with time because it's an elliptical orbit.

同样的，第五个方程序，中的速度同样，会随时间改变，因为这是椭圆形轨道。

youdao

So that's the definition of v, instantaneous velocity.

这些就是v的定义，也就是瞬时速度。

youdao

So, the two most elementary ideas you learn are what is the average velocity of an object, as then ordered by the symbol v-bar.

你们学过的两个最基本的概念是,物体的平均速度,用"v拔"表示

耶鲁公开课 - 基础物理课程节选