Q8. A small ball of mass $m$ and density $\rho$ is dropped in a viscous liquid of density $\rho _ { 0 }$. After sometime, the ball falls with constant velocity. The viscous force on the ball is :\\
(1) $m g \left( 1 - \rho \rho _ { 0 } \right)$\\
(2) $m g \left( 1 + \frac { \rho } { \rho _ { 0 } } \right)$\\
(3) $m g \left( \frac { \rho _ { 0 } } { \rho } - 1 \right)$\\
(4) $m g \left( 1 - \frac { \rho _ { 0 } } { \rho } \right) _ { \nabla }$