A cylindrical tank of diameter D

A cylindrical tank of diameter D contains liquid to an initial height ho. At time t = 0 a small stopper of diameter d is removed from the bottom. Using Bernoulli€™s equation with no losses, derive (a) a differential equation for the free-surface height h (t) during draining and (b) an expression for the time to drain the entire tank.

A cylindrical tank of diameter D