Q. A wheel is rotating at $900\ r.\ p.\ m.$ about its axis. When the power is cut-off, it comes to rest in 1 minute. The angular retardation in $radian/s^{2}$ is
A) $\pi/2$
B) $\pi/4$
C) $\pi/6$
D) $\pi/8$
Explanation
(a) $\omega_{1} = \frac{900}{60} \times 2\pi = 30\pi\ rad/s,\omega_{f} = 0,t = 60s$
$\omega_{f} = \omega_{t} + \alpha t\ \therefore\alpha = \frac{\omega_{f} - \omega_{t}}{t} = \frac{0 - 30\pi}{60} = - \frac{\pi}{2}rad/s^{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.