$M{\omega ^2}x = \left[ {\rho Ag + k} \right]x$
$ \Rightarrow \omega = {\left[ {\frac{{\rho Ag + k}}{m}} \right]^{1/2}}$
$ \Rightarrow T=2\pi {\left[ {\frac{M}{{\left( {k + A\sigma g} \right)}}} \right]^{1/2}}$
It Should be less than $2\pi {\left[ {\frac{M}{{\left( {k + A\sigma g} \right)}}} \right]^{1/2}}$

$x = 3\,sin\, 20\pi t + 4\, cos\, 20\pi t$ ,
where $x$ is in $cms$ and $t$ is in $seconds$ . The amplitude is ..... $cm$


