Question

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. \( F = Mg \left( 1 + \frac{\rho}{\rho_0} \right) \)
• C. \( F = Mg \left( 1 + \frac{\rho_0}{\rho} \right) \)
• D. \( F = Mg \left( 1 \pm \rho \rho_0 \right) \)

Hint:

In problems involving viscous force and terminal velocity, remember that at terminal velocity:
The weight of the object is balanced by the sum of buoyant and viscous forces.