This is the one that makes the speed change along the circumference.
这是导致速度，沿着圆周改变的因素。
2
And that linear velocity, which, in this case, is really your speed, is of course the circumference of the circle divided by how many seconds it takes to go around.
线速度，在这个例子里，就是速率，是这个圆环的周长，除以走一圈，需要的秒数。
3
The waistline and thigh circumference are the main factors that affect the ball speed of frontal header.