Physics - Fluid Question with Solution | TestHub

The buoyant force is given by 

$B=V{\rho }_{0}g$

where $V$ is the volume of the ball. The weight of the ball

$W=Mg=V\rho g$, is acting in the opposite direction of the buoyant force . Hence, at terminal velocity

$Mg-B=F_v$

$\Rightarrow B+F_v=Mg$

$$\begin{gathered} \Rightarrow F_v=V\rho g-V{\rho }_{0}g \\ \Rightarrow F_v=\rho Vg(1-\frac{{\rho }_0}{\rho }) \\ \Rightarrow F_v=Mg(1-\frac{{\rho }_0}{\rho }) \end{gathered}$$