**INTRODUCTION **

Rotational motion is a kind of motion in which the body follows a curved path. For example, the wheel of the car or train is in constant rotational motion.

**DIFFERENCES BETWEEN LINEAR AND ROTATIONAL MOTION **

In a linear motion, a body follows straight paths. The attributes which define any linear motion are displacement, velocity, acceleration, momentum and force applied to move he body. Where as, attributes used to define any rotational motion are angular displacement, angular velocity and acceleration, angular momentum and torque. The formula for all of these is in parallel to formula of attributes in the linear motion.

**SIMILARITY BETWEEN LINEAR AND ROTATIONAL MOTION **

In linear motion we define, velocity as –

Velocity = displacement / time

In rotational motion we define angular velocity (rate of change of angle with respect to time) as–

Angular velocity (w) = Dq / Dt

where Dq is the angular displacement and Dt is the time taken to make this displacement.

In linear motion we define we define force as,

F = Dp / Dt = ma

where Dp is the change in linear momentum in time Dt, m is the mass of the body and a is the acceleration of the body.

In rotational motion we define torque as the rotational analogue.

t = DL / Dt = I * a

where L is the angular momentum analogous to linear momentum p, I is moment of inertia which is analogous to mass of the body m, a is the angular acceleration which is analogous to linear acceleration a.

**SOME FACTS ABOUT ROTATIONAL MOTION **

Circular motion is just a type of rotational motion. In Circular motion the body follows the fixed path, while in rotational motion a body can follow any curved path. Mathematically, writing formulas for rotation in three dimensions gets complicated because the axis of rotation is liable to changing direction.

**SOME EXAMPLES OF ROTATIONAL MOTION **

Any curveball has a rotational motion and a projectile motion as well. It rotates within itself and also follows the trajectory path. Similarly, earth rotates at its own axis and also rotates around Sun in another orbit. Rotation of worm driver over worm gear is another example. A person performing a Somersault, is an example of rotational motion. When we open a cap of any soda bottle, it jumps up in the air because of pressure released and is an example of rotational motion. Fan moving in the house, table fan, hand blender’s blades motion are all examples of rotational motion.