Just as we have linear displacement, linear velocity and linear acceleration, in case of objects moving in a circular path, we have angular displacement, angular velocity and angular acceleration.

Consider a stone tied to a string and whirled around. At a particular instant of time, it makes an angle θ from the origin. Thus, the angle traced out by the radius vector at the axis of the circular path in a given time is called angular displacement.

The rate of change of angular displacement is called angular velocity ω = dθ / dt and its unit is rad/s

The rate of change of angular velocity is called angular acceleration a = r ω² and it is directed towards the centre of the circle.

While solving problems, we resolve the horizontal and vertical components of force acting on a body and equate them together, as in other linear motion problems. Hence, if you know about this basics, it will be easy to solve problems involving rotation.