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

$\begin {array} {1 1} (a)\;\frac{\pi}{2} & \quad (b)\;\frac{\pi}{4} \\ (c)\;\frac{\pi}{6} & \quad (d)\;\frac{\pi}{8} \end {array}$

Can you answer this question?

Initial angular velocity is 900 rpm
$\omega = 900 \times \large\frac{2 \pi}{60}$
$\qquad= 30 \pi$
$\alpha = \large\frac{30 \pi -0}{60}$
$\qquad= \large\frac{\pi}{2}$
Hence a is the correct answer.
answered Nov 25, 2013 by
edited Jul 31, 2014 by meena.p