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?
\( F = Mg\left(1-\dfrac{\rho_{0}}{\rho}\right) \)
\( F = Mg\left(1+\dfrac{\rho}{\rho_{0}}\right) \)
\( F = Mg\left(1+\dfrac{\rho_{0}}{\rho}\right) \)
\( F = Mg\left(1 \pm \rho\rho_{0}\right) \)