# Solve the following :

Question:

A driver having a moment of inertia of $6.0 \mathrm{~kg}_{-} \mathrm{m}^{2}$ about an axis through its centre of mass rotates at an angular speed of $2 \mathrm{rad} / \mathrm{s}$ about the axis. If he folds his hands and feet to decrease the moment of inertia to $5.0 \mathrm{~kg}_{-} \mathrm{m}^{2}$, what will be the new angular speed?

Solution:

Since, ${ }^{\tau_{\text {ext }}}=0$

$\quad \approx L_{i}=L_{f}$

$6(2)=5^{\omega_{f}}$

$\omega_{f}=2.4 \mathrm{rad} / \mathrm{sec}$