\(\frac{1}{2} I w_{i}^{2}=200\)

\(w_{i}^{2}=\frac{200 \times 2}{I}=\frac{400}{4}=100\)

\(w_{i}=10 \mathrm{rad} / \mathrm{sec}\)

\(\zeta=T \alpha\)

\(5=4 \alpha\)

\(\alpha=5 / 4 r a d / s e c^{2}\)

\(w_{t}=0\)

\(w_{t}^{2}=w_{i}^{2}+2 \alpha \theta\)

\(0=100+2\left(\frac{-5}{4}\right) \times \theta\)

\(\theta=40\) radians

So number of revolution \(=\frac{\theta}{2 \pi}\)

\(=\frac{40}{2 \pi}=6.4\)

\(6.4 \,revolution\)