Angle traversed by a body in circular motion in unit time is called angular velocity.OR The rate of change of angular position of a body is called angular velocity. Consider a particle “P” moving in a circular path of radius “r”. The angular position P_{1 }is q_{1} at instant t_{1} and q_{2} at instant t_{2}.

The angular displacement is q_{2} – q_{1} = Dq . Time interval = t_{2} –t_{1} =Dt Since the angle traced per sec by a body moving in circle is called its average angular speed denoted byw_{av.} Therefore, w_{av} = Dq / DtUnit for angular velocity is rad /sec OR rev/sec.

INSTANTANEOUS ANGULAR VELOCITY

The angular velocity at a particular instant is called instantaneous angular velocity. If D t is very small i.e. D t è 0 then Dq / Dt is called instantaneous angular velocity. Unit for angular velocity is rad /sec OR rev/sec.

DIRECTION OF ANGULAR VELOCITY

Direction of angular velocity is given by right-hand rule, which states that if we curl the fingers of right hand in the direction of rotation then thumb will represent the direction of angular velocity.

ANGULAR ACCELERATION

Rate of change of angular velocity of a body is called angular acceleration. It is denoted by a . If w_{1} is angular velocity of a body moving in circle at instant t_{1} and w_{2} is angular velocity of body at instant t_{2} then,

if Dt is very small then acceleration is called instantaneous angular acceleration.