Work-Energy Theorem

If the differential equation for a simple harmonic motion is $\frac{{\mathrm{d}}^{2}y}{\mathrm{d}{t}^2}+2y=0$, the time period of the motion is,

Tube $A$ has both ends open while tube $B$ has one end closed. Otherwise, they are identical. The ratio of fundamental frequency of tube $A$ and $B$ is,