# Circular Motion

Circular Motion

Introduction:

Physics deals with various types of motions. In daily life we come across various practical situations involving motion. A cyclist travelling along a straight road performs rectilinear (linear) motion. A cyclist taking turn along a curved road, perform a curvilinear motion. A cyclist moving along a circular race course track perform a circular motion.

The circular motion is a special case of linear or translator motion, in which particle revolves along circumference of a circle.

Following are some examples of a circular motion.

(1)   Motion of earth and other planets around the sun.
(2)   Motion of an object tied at the end of a string and whirled in a circle.
(3)   Motion of tip of minute hand, hour hand and second hand of a clock.

(4)   Motion of roller coaster looping the loop.

Angular Displacement: Angular displacement is defined as the angle described by radius vector in a                                   given time at the centre of circle.

Angular Velocity: Angular velocity of a particle performing circular motion is defined as the time                              rate of change of angular displacement.

The S.I. unit of angular velocity is rad/s.

The direction of angular velocity is given by right hand rule and is in the direction of angular displacement.

Angular acceleration: The angular acceleration is defined as the time rate of change of angular                                          velocity.
The S.I. unit of angular acceleration is rad/s2

e.g. When an electric fan is switched on, the blades of fan move with increasing angular velocity with time. The angular acceleration in this case will have same direction as the angular velocity. When the electric fan is switched off, the angular velocity of blades of fan decreases with time. The angular acceleration now will have direction opposite to that of angular velocity.

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