\( \omega \,\, = \,\,2\pi \,\, \times \,\,12\,\, = \,\,24\pi \,\,rad\,/s \)
\( \omega \,\, = \,\,{\omega _0}\,\, + \;\,\alpha \tau \,\,\)
\(\therefore \,\,0\,\, = \,\,24\pi \, - \,\,\alpha t\,\,\)
\(\therefore \,\,\alpha \,\, = \,\,\frac{{24\pi }}{8}\,\, = \,\,3\pi \, \)
\( \alpha \,\, = \,\,\tau \,\,\therefore \,\,\frac{{24}}{\pi }\,\, \times \,\,3\pi \,\,\)
\(\therefore \,\,\tau \,\, = \,\,72\,\,N\,\, - \,\,m \)