Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 11

# A Kid of Mass M Stands at the Edge of a Platform of Radius R Which Can Be Freely Rotated About Its Axis. the Moment of Inertia of the Platform is I. - Physics

Sum

A kid of mass M stands at the edge of a platform of radius R which can be freely rotated about its axis. The moment of inertia of the platform is I. The system is at rest when a friend throws a ball of mass m and the kid catches it. If the velocity of the ball is $\nu$ horizontally along the tangent to the edge of the platform when it was caught by the kid, find the angular speed of the platform after the event.

#### Solution

On considering two bodies as a system, we get

Moment of inertia of kid and ball about the axis

$= \left( M + m \right) R^2$

Applying the law of conservation of angular momentum, we have

$m\nu R = \left\{ I + \left( M + m \right) R^2 \right\} \omega$

$\Rightarrow \omega = \frac{m\nu R}{I + \left( M + m \right) R^2}$

Is there an error in this question or solution?

#### APPEARS IN

HC Verma Class 11, 12 Concepts of Physics 1
Chapter 10 Rotational Mechanics
Q 56 | Page 198