### Rotational Kinematics

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**October 15th, 2013, 1:44 am**Angular displacement: The angle through which a rigid object rotates about a fixed axis. By convention, this quantity is positive if the rotation is counterclockwise, negative if it is clockwise. Units are radians (rad).

Radian: An SI unit of angular displacement defined as the circular arc length s traveled by a point on a rotating body divided by the radial distance r of the point from the axis:

Radian: An SI unit of angular displacement defined as the circular arc length s traveled by a point on a rotating body divided by the radial distance r of the point from the axis: