$A$ wheel of radius $30 \ cm$ rotates about its axis and undergoes an angular displacement of $30^\circ$. The linear distance covered by the wheel is .......

An athlete completes one round of a circular track of radius $R$ in $40 \,s$. What will be his displacement at the end of $2 \,min \,20 \,s$?

$A$ particle is moving with a constant speed $v$ in a circle. What is the magnitude of average velocity after half rotation?

If a particle covers half the circle of radius $R$ with constant speed $v$,then:

Assertion $(A)$ :- If a body is in a state of uniform circular motion,then its velocity and acceleration both are varying.
Reason $(R)$ :- If the magnitude of velocity is $v$ and the radius of uniform circular motion is $r$,then the magnitude of acceleration is $v^2/r$.

If a body is moving in a circle of radius $r$ with a constant speed $v$,its angular velocity is: