PYQ NEET- Rotational Motion L-5

Question: The angular speed of a fly wheel moving with uniform angular acceleration changes from $1200 \mathrm{rpm}$ to $3120 \mathrm{rpm}$ in 16 seconds. The angular acceleration in $\mathrm{rad} / \mathrm{s}^2$ is#

A) $2 \pi$

B) $4 \pi$

C) $12 \pi$

D) $104 \pi$

Answer: $4 \pi$#

Solution:#

Angular acceleration $\alpha=\frac{\omega_f-\omega_i}{t}$ $$ \begin{aligned} & \omega_f=3120 \times \frac{2 \pi}{60} \mathrm{rad} / \mathrm{s} \ & \omega_i=1200 \times \frac{2 \pi}{60} \mathrm{rad} / \mathrm{s} \ & \Rightarrow \alpha=\frac{(3120-1200)}{16} \times \frac{2 \pi}{60}=4 \pi \end{aligned} $$