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?

• A

  $F=Mg\left(1+\frac{{\rho }_0}{\rho }\right)$
• B

  $F=Mg\left(1+\frac{\rho }{{\rho }_0}\right)$
• Correct answer
  C

  $F=Mg\left(1-\frac{{\rho }_0}{\rho }\right)$
• D

  $F=Mg\left(1\pm \rho {\rho }_0\right)$

Hence, the correct answer is option: 'C'.