A cylindrical block of wood (density \(= 650\mathrm{kg}\mathrm{m}^{-3}\) of base area \(30\mathrm{cm}^2\) and height \(54~\mathrm{cm}\) , floats in a liquid of density \(900\mathrm{kg}\mathrm{m}^{-3}\) . The block is depressed slightly and then released. The time period of the resulting oscillations of the block would be equal to that of a simple pendulum of length (nearly)