Q. A wheel having moment of inertia $2\ kg - m^{2}$ about its vertical axis, rotates at the rate of $60\ rpm$ about this axis. The torque which can stop the wheel’s rotation in one minute would be
A) $\frac{2\pi}{15}N - m$
B) $\frac{\pi}{12}N - m$
C) $\frac{\pi}{15}N - m$
D) $\frac{\pi}{18}N - m$
Explanation
(c) $\alpha = \frac{2\pi(n_{2} - n_{1})}{t} = \frac{2\pi\left( 0 - \frac{60}{60} \right)}{60} = \frac{- 2\pi}{60} = \frac{- \pi}{30}rad/\sec^{2}$
$\therefore\tau = I\alpha = \frac{2 \times \pi}{30} = \frac{\pi}{15}N - m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.