**Definition**

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 P1 is q1 at instant t1 and q2 at instant t2.

The angular displacement is q2 – q1 = Dq .

Time interval = t2 –t1 =Dt

Since the angle traced per sec by a body moving in circle is called its average angular speed

denoted by wav.

Therefore, wav = 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 w1 is angular velocity of a body moving in circle at instant t1 and w2 is angular velocity of body at

instant t2 then,

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

**Unit**

Unit of angular acceleration is rad/sec2.

**Direction**

Direction of angular acceleration is same as of w.

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