A ball of radius r and density r 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 h, the value of h is given by

\[\frac{2}{9}{{r}^{4}}{{\left( \frac{\rho -1}{\eta } \right)}^{2}}g\]

\[\frac{2}{9}{{r}^{2}}\left( \frac{1-\rho }{\eta } \right)\,g\]

\[\frac{2}{81}{{r}^{2}}\left( \frac{\rho -1}{\eta } \right)\,g\]

\[\frac{2}{81}{{r}^{4}}{{\left( \frac{\rho -1}{\eta } \right)}^{2}}g\]

A ball of radius r and density r falls freely under gravity through a

1.	A ball of radius r and density r 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 h, the value of h is given by
A.	\[\frac{2}{9}{{r}^{2}}\left( \frac{1-\rho }{\eta } \right)\,g\]
B.	\[\frac{2}{81}{{r}^{2}}\left( \frac{\rho -1}{\eta } \right)\,g\]
C.	\[\frac{2}{81}{{r}^{4}}{{\left( \frac{\rho -1}{\eta } \right)}^{2}}g\]
D.	\[\frac{2}{9}{{r}^{4}}{{\left( \frac{\rho -1}{\eta } \right)}^{2}}g\]
Answer» D. \[\frac{2}{9}{{r}^{4}}{{\left( \frac{\rho -1}{\eta } \right)}^{2}}g\]