Question

A wheel is rotating at $900 \,r.p.m$. about its axis. When power is cut off it comes to rest in 1 minute. 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

Answer: (A)

Angular retardation, $\alpha=\frac{\omega_{2}-\omega_{1}}{t}$
$=\frac{2 \pi\left(n_{2}-n_{1}\right)}{t}$
$=\frac{2 \pi\left(0-\frac{900}{60}\right)}{60}$
$=\frac{\pi}{2} \,rad / s ^{2}$