• # question_answer 43) 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)  $\pi /2$                       B)  $\pi /4$C)  $\pi /6$                       D)  $\pi /8$

Angular retardation, $\alpha =\frac{{{\omega }_{2}}-{{\omega }_{1}}}{t}=\frac{2\pi ({{n}_{2}}-{{n}_{1}})}{t}=\frac{2\pi (0-900/60)}{60}=\frac{\pi }{2}rad/{{s}^{2}}.$