Physics - Fluid Question with Solution | TestHub

Stoke's law : $6\pi R\eta v=\frac{4}{3}\pi R^3(\rho -\sigma )g$ $\therefore v\propto R^2$. As $M$ is given, $\rho =\frac{M}{\frac{4}{3}\pi R^3}$ But as $R^3$ increases, $M$ also increases and $\rho$ is a constant. $\sigma$ also is a constant. $\therefore v$, the terminal velocity $\propto R^2$.