\(v = \frac{{dx}}{{dt}} = - A\omega \sin \left( {\omega \,t + \frac{\pi }{4}} \right)\)
For maximum speed, \(\sin \,\left( {\omega \,t + \frac{\pi }{4}} \right) = 1\)
==> \(\omega \,t + \frac{\pi }{4} = \frac{\pi }{2}\) or \(\omega \,t = \frac{\pi }{2} - \frac{\pi }{4}\)
==> \(t = \frac{\pi }{{4\omega }}\)
($g = \pi ^2$ )