One way is to say, if I do a full revolution, I think of the speed as a distance over time.

一种方法是,如果我转完整的一圈,我认为速度就是距离除以时间

耶鲁公开课 - 基础物理课程节选

Whenever you see a particle moving in a circle, even if it's at a constant speed, it has an acceleration, v square over r directed towards the center.

只要看到质点做圆周运动,即使是匀速圆周运动,也存在一个加速度,大小为 v^2 / r,方向指向圆心

耶鲁公开课 - 基础物理课程节选