## Physics XI Content

# CIRCULAR MOTION-ANGULAR MOTION-RADIAN

CIRCULAR MOTION-ANGULAR MOTION-RADIAN | |||

UNIFORM CIRCULAR MOTION | |||

When an object moves in a circular path such that the magnitude of velocity is constant then, the motion is called uniform circular motion. | |||

ANGULAR MOTION | |||

When a body moves along a circular path it traverses a certain angle in a given interval of time. This type of motion is called ‘angular motion‘. | |||

ANGULAR DISPLACEMENT | |||

“The angle traveled by a body during its motion arounda circular path is called its angular displacement.” Consider a particle moves in a circular path from a point P _{1} to P_{2} in an interval of time Dt. It travels an angle <p _{1}OP_{2} =q which is called angular displacement of the particle. | |||

RADIAN | |||

One radian is the angle traced by an arc of length equal to radius of circle.Length of circular track of radius r is 2p r. Therefore numbers of radians in a circle of radius r will be =2p r / r = 2pAngle at the centre of circle in one complete rotation = 360^{o} = 2p rad 180^{o} = p rad or 1^{o} = p / 180 rad. | |||

RELATION BETWEEN LENGTH OF ARC AND THE ANGLE SUBTENDED | |||

The length of arc “S” is directly proportional to angle q subtended (measured in radians) traced at the centre of circle by ends of the arc. | |||

S a q | |||

S = rq | |||

Where r is radius of circle. | |||