 Since point "P" and "O"2 have only one velocity,

The above two yields that

Since the point "P" (and thus formula_126) is arbitrary, it follows that

If the reference point is the instantaneous axis of rotation the expression of the velocity of a point in the rigid body will have just the angular velocity term.This is because the velocity of the instantaneous axis of rotation is zero.An example of the instantaneous axis of rotation is the hinge of a door.