\(\alpha=\frac{2 \times 200}{20 \times(0.2)}=10 rad / s ^{2}\)
\(\omega^{2}=\omega_{0}^{2}+2 \alpha \Delta \theta\)
\((50)^{2}=0^{2}+2(10) \Delta \theta \Rightarrow \Delta \theta=\frac{2500}{20}\)
\(\Delta \theta=125 rad\)
No. of \(=\frac{125}{2 \pi} \approx 20\) revolution