Angular Displacement

Angular displacement is the angle that a rotating body goes through. For example, if a skater skates in a circle around the center of the rink, stopping and starting at the same place, his or her angular displacement would be 360 degrees. The direction of the rotation is important. If the skater makes a counterclockwise circle that is a positive 360 degree displacement. However, if the skater makes a clockwise circle it is a negative 360 degree displacement. Thus if a skater were to switch directions and skate half a circle counter clockwise, turn around and skate back clockwise, he has displaced positive 180 degrees and then negative 180 degrees for a total displacement of zero. Angular displacement is measured in radians (SI units) or degrees or revolutions (English units).

An illustration of angular displacement is provided below. The skater on the right has a negative 270 degree displacement. The skater on the left has a positive 90 degree displacement.