Sometimes they give you the speed in miles per hour, kilometers per year, pounds per square foot.

有时候速度的单位是英里/小时,千米/年,英磅/平方米

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