In an experiment to verify Stokes law, a small spherical ball of radius r and density ρ falls under gravity through a distance h in air before…

In an experiment to verify Stokes law, a small spherical ball of radius r and density $\displaystyle \rho$ falls under gravity through a distance $\displaystyle h$ in air before entering a tank of water. If the terminal velocity of the ball inside water is same as its velocity just before entering the water surface, then the value of h is proportional to : (ignore viscosity of air)