...problems in angular velocity and momentum are more conveniently done by working in radian measure.

A radian is an arc of a circle equal in length to the radius of that circle. A radian is about 57.3 degrees. It is defined that way so that there are 2 x Pi radians in a full circle. That is, 1 revolution = 360 degrees = 6.28 radians.

If a spinning object of radius 1 gazinga* is spinning at 100 RPM, a point on its edge has a velocity of 628 gazingas
per minute. The relationship is linear, so if you double the size of the object, the linear velocity of the point also doubles.

*The gazinga is the Klingon unit of length.