Question

A wheel is rotating at $900 \,rpm$ about its axis. When the power is cut off it comes to rest in $1$ min. The angular retardation in $rad/s^{-2}$ is

• A. $\frac{\pi}{2}$
• B. $\frac{\pi}{4}$
• C. $\frac{\pi}{6}$
• D. $\frac{\pi}{8}$

Answer 1

The Correct Option is A

Use $\omega= \omega_0 + \alpha t$ Here , $\omega_0= 900 \,rpm = \frac{(2\pi \times 900)}{60}rad/s$ $\omega =0$ and $t = 60$ $0= \frac{2\pi \times 900}{60} + \alpha \times 60$ $\alpha = \frac{2\pi \times 900}{60 \times 60}$ = $\frac{\pi}{2}$