Physics - Fluid Question with Solution | TestHub

The terminal velocity of a sphere of radius $r$ and density $\rho$, immersed in a liquid of density $\sigma$ and viscosity $\eta$ is given by $v_{\mathrm{T}}=\frac{2}{9}\frac{\left(\rho -\sigma \right)r^{2}g}{\eta }$

Hence, for spherical raindrop, $v_{\mathrm{T}}\propto r^2$.