Physics - Fluid Question with Solution | TestHub

A spherical ball of density $\rho$ and radius $3\mathrm{mm}$ is dropped into a tube containing a viscous liquid filled upto $0$ mark as shown in the figure. Viscosity of the liquid is $1.260\mathrm{N}s/{\mathrm{m}}^2$ and its density is ${\rho }_L=\rho /2=1260kg/{\mathrm{m}}^3$. Assume the ball reaches a terminal speed by the $10\mathrm{cm}$ mark. The time taken by the ball to travel the distance between the $10\mathrm{cm}$ and $20\mathrm{cm}$ mark is (take $g=10m/{\mathrm{s}}^2$)