MCQ
A ball of radius $r $ and density $\rho$ falls freely under gravity through a distance $h$ before entering water. Velocity of ball does not change even on entering water. If viscosity of water is $\eta$, the value of $h$ is given by
- A$\frac{2}{9}{r^2}\left( {\frac{{1 - \rho }}{\eta }} \right)\,g$
- B$\frac{2}{{81}}{r^2}\left( {\frac{{\rho - 1}}{\eta }} \right)\,g$
- ✓$\frac{2}{{81}}{r^4}{\left( {\frac{{\rho - 1}}{\eta }} \right)^2}g$
- D$\frac{2}{9}{r^4}{\left( {\frac{{\rho - 1}}{\eta }} \right)^2}g$
