$\mathrm{O}=\mathrm{A} \sin (\omega+\phi)$ as $\mathrm{x}=0$ at $\mathrm{t}=1 \mathrm{s}$
and $\mathrm{v}=\mathrm{A} \omega \cos (\omega \mathrm{t}+\phi)$
$\frac{1}{4}=\mathrm{A} \omega \cos (2 \omega+\phi)$ as $\mathrm{v}=\frac{1}{4} \frac{\mathrm{M}}{\mathrm{s}}$ at $\mathrm{t}=2 \mathrm{s}$
$\text { here } \omega=\frac{2 \pi}{6}=\frac{\pi}{3} \quad \text { as } \mathrm{T}=6 \mathrm{s}$
$x = a\,\sin \,\left( {\omega t + \pi /6} \right)$
After the elapse of what fraction of the time period the velocity of the particle will be equal to half of its maximum velocity?