If the position and velocity of the particle at $t=0\, {s}$ are $2\, {cm}$ and $2\, \omega \,{cm} \,{s}^{-1}$ respectively, then its amplitude is $x \sqrt{2} \,{cm}$ where the value of $x$ is ..... .
$v(t)=A \omega \cos (\omega t+\phi)$
$2=A \sin \phi.....(1)$
$2 \omega=A \omega \cos \phi.....(2)$
From $(1)$ and $(2)$
$\tan \phi=1$
$\phi=45^{\circ}$
Putting value of $\phi$ in equation $(1)$
$2=A\left\{\frac{1}{\sqrt{2}}\right\}$
$A=2 \sqrt{2}$
$x=2$