Q116 / 125 · BITSAT 2020 · Physics
A wheel is rotating at $900 \mathrm{r}$.p.m. about its axis. When power is cut offit comes to rest in 1 minute. The angular retardation in $\mathrm{rad} / \mathrm{s}^{2}$ is
- Correct answerA$\pi / 2$
- B$\pi / 4$
- C$\pi / 6$
- D$\pi / 8$
Solution
Angular retardation,
$\begin{aligned} \alpha &=\frac{\omega_{2}-\omega_{1}}{t}=\frac{2 \pi\left(\mathrm{n}_{2}-\mathrm{n}_{1}\right)}{\mathrm{t}} \\ &=\frac{2 \pi(0-900 / 60)}{60}=\frac{\pi}{2} \mathrm{rad} / \mathrm{s}^{2} \end{aligned}$
Hence, the correct answer is option: 'A'.