\(\therefore \,\,\,\,I\,\, = \,\,100\,\,kg\,\, \times \,\,{m^2}\,\,\)
\(\therefore \,\,\,\tau \,\, = \,\,1\alpha \)
\( 400\,\, = \,\,100\,\,\alpha \,\,\)
\(\therefore \,\,\alpha \,\, = \,\,4\,\,\)
\(\therefore \,\,\,\omega \,\, = \,\,{\omega _0}\,\, + \;\,\alpha t\,\,\,\,\)
\(\therefore \,\,\,\,{\omega _0}\,\, = \,\,0 \)
\( \omega \,\, = \,\,0\,\, + \;\,4\,\, \times \,\,4\,\, = \,\,16\,\,rad/s \)