Eli5: How is the speed of a rotating object defined (e.g. a windmill) if you don‘t use rpm. Where do you measure the speed in mph?

Question

I had a look at a huge windmill and was wondering how fast the blades are spinning. Obviously, the distance the blades make is different on the outside than on the inside. Is the speed of a rotating object always measured in rpm and not in mph?

In: 3

Answer 1

Angular velocity is the technical term for rotational speed not expressed in RPM.

Angular velocity is usually stated in radians per second (rads^-1 ), there being 2.pi radians in a complete circle.

Some conversion function is required (if desired) to convert to degrees.