The rate of change of the angular velocity with time, or the second derivative of the angular position with respect to time. For systems rotating about a single axis with a fixed moment of inertia about that axis, the angular acceleration is directly proportional to the net torque acting on the system. Although it is a vector quantity, having both direction and magnitude, we will consider only cases where α is parallel to omega. It is usually represented by the small Greek letter alpha, α.
