Q 11-09-094JEE MainJEE Main 2023 (6 Apr, Shift 1)Easy
A small ball of mass $M$ and density $\rho$ is dropped in a viscous liquid of density $\rho_0$. After some time, the ball falls with a constant velocity. What is the viscous force on the ball?
Answer: (C) $F=Mg\left(1-\dfrac{\rho_0}{\rho}\right)$
At terminal velocity, weight $=$ buoyancy $+$ viscous force. Buoyancy $=\dfrac{M}{\rho}\rho_0g$.
$$F=Mg-\frac{M\rho_0g}{\rho}=Mg\left(1-\frac{\rho_0}{\rho}\right)$$
Solution by Sreeraj P, M.Sc Physics