Question

A circular disc is rotating with angular velocity $\omega$. A man standing at the edge walks towards the centre of disc, then the angular velocity $\omega$:

• A. decreases
• B. no change
• C. increases
• D. halved

Answer 1

The correct option is C increases

$L_1=L_2(\because$ Net external torque is zero)
$I_1{\omega }_1=I_2{\omega }_2$
$(m{R}^2+\frac{{mR}^2}{2})\omega =\left({mR}^2\right){\omega }_2$
${\omega }_2=\frac{\omega (2m+m)}{m.}$
$\therefore \omega$ will increase (as moment of inertia decreases.)