$($b$)$ A $\frac{1}{30}$ th scale model of the submarine is tested in a wind tunnel. For a wind speed

of $40\frac{m}{s},$ the drag force measured for the model in wind tunnel is $1$ KN $.$ Estimate

the drag force on the prototype submarine and the corresponding speod of the

submarine following similarity analysis. Take density of sea water as $1050k\frac{g}{m^3}$

and that of wind as $1\mathrm{.}2k\frac{g}{m^3}.$ The kinematic viscosity of sea water is $0\mathrm{.}01$ Stokes

and that of wind is $0\mathrm{.}015$ Stokes.