A rectangular block having mass mand cross sectional area A is floating in a liquid having density r. If this block in its equilibrium position is given a small vertical displacement, its starts oscillating with periodic time T. Then in this case…..
$ Restoring force F = - Ay \rho g = -( A \rho g ) y = -ky $ $ \therefore k = A \rho g \Rightarrow T = 2 \pi \sqrt { m \over k } \Rightarrow T \alpha { 1 \over sqrt A^1 } $