Question

A disc rotating about its axis with A angular speed $\omega_o$ is placed lightly (without any translational push) on a perfectly frictionless table. The radius of the disc is $R$.

Let $v_A, v_B$ and $v_C$ be the magnitudes of linear velocities of the points $A, B$ and $C$ on the disc as shown. Then

• A. $v_{A} > v_{B} > v_{C}$
• B. $v_{A} < v_{B} < v_{C}$
• C. $v_{A} = v_{B} < v_{C}$
• D. $v_{A} = v_{B} > v_{C}$

Answer 1

Answer: (D)

Velocity at point on the disc, $v = r\omega$
where $r$ is the distance of point from $O$.
$\therefore v_{A} = R\omega_{0} $
$ v_{B} = R\omega_{0} $
$ v_{C} = \frac{R}{2}\omega_{0} $
$ \therefore v_{A} = v_{B} > v_{C}$