A small spherical ball of radius 0.1 mm and density $10^4 \mathrm{~kg~m}^{-3}$ falls freely under gravity through a distance $h$ before entering a tank of water. If, after entering the water the velocity of ball does not change and it continues to fall with same constant velocity inside water, then the value of $h$ will be $\_\_\_\_$ m. (Given $g = 10 \mathrm{~m~s}^{-2}$, viscosity of water $= 1.0 \times 10^{-5} \mathrm{~N\text{-}s~m}^{-2}$).