A disc thrower starts his spin while standing facing the back of the circle. He releases the discus 2 seconds later after spinning 540° to his left. Assume that he accelerates at a constant rate.  a) What was his ANGULAR ACCELERATION during the throw? b) How fast was he spinning after the first half-revolution (180°)? c) How fast was he spinning at the time of release of the discus?

Definition Definition Rate of change of angular velocity. Angular acceleration indicates how fast the angular velocity changes over time. It is a vector quantity and has both magnitude and direction. Magnitude is represented by the length of the vector and direction is represented by the right-hand thumb rule. An angular acceleration vector will be always perpendicular to the plane of rotation. Angular acceleration is generally denoted by the Greek letter α and its SI unit is rad/s 2 .