Q 11-06-118JEE MainJEE Main 2023 (11 Apr, Shift 2)Easy
A circular plate is rotating in horizontal plane, about an axis passing through its centre and perpendicular to the plate, with an angular velocity $\omega$. A person sits at the centre having two dumbbells in his hands. When he stretches out his hands, the moment of inertia of the system becomes triple. If $E$ be the initial kinetic energy of the system, then final kinetic energy will be $\dfrac Ex$. The value of $x$ is ______.
Numerical value type. Enter your answer.
Answer: 3
Angular momentum is conserved and $K=\dfrac{L^2}{2I}$, so tripling $I$ makes $K=\dfrac E3$. $x=3$.
Solution by Sreeraj P, M.Sc Physics