A Goniometer can be used to measures angle, angular velocity and angular acceleration of the movements of an elbow and knee. The Goniometer Probe consists of two arms and a potentiometer. As the angle between the arms changes, the resistance of the potentiometer changes. The angle sensor, connected to the probe, measures the resistance of the potentiometer and converts it to an angle measurement. If the measured angular displacement from a knee movement is 90 degree in 2 seconds, what is the average angular velocity?