# Rotational velocity

#### einsteinian77

How could i calculate the velocity of an object rotated around a fixed point such as a hand on a clock. It seems as though each section of the hand would have a different velocity, the end part being the fastest while the beginning part being the slowest if not moving at all. Im guessing the velocity would be expressed in frequency somehow.

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#### arcnets

Originally posted by einsteinian77
Im guessing the velocity would be expressed in frequency somehow.
That's correct, einsteinian77. Since the rotational velocity v increases proportional with radius r (distance from center), you define the angular velocity
[nu] = v/r.
This is the same for all points. The unit is 1/s. You could also say it's radians per second, since by integrating you get the angle:
[alpha] = a/r
where a is the arc length, and [alpha] is measured in radians.

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