Which of the following is the incorrect graph for a sphere falling in a viscous liquid? (Given at $t = 0$,velocity $v = 0$ and displacement $x = 0$.)

Two spheres $P$ and $Q$ of equal radii have densities $\rho_1$ and $\rho_2$,respectively. The spheres are connected by a massless string and placed in liquids $L_1$ and $L_2$ of densities $\sigma_1$ and $\sigma_2$ and viscosities $\eta_1$ and $\eta_2$,respectively. They float in equilibrium with the sphere $P$ in $L_1$ and sphere $Q$ in $L_2$ and the string being taut (see figure). If sphere $P$ alone in $L_2$ has terminal velocity $\overrightarrow{V}_{P}$ and $Q$ alone in $L_1$ has terminal velocity $\overrightarrow{V}_{Q}$,then
$(A)$ $\frac{|\overrightarrow{V}_{P}|}{|\overrightarrow{V}_{Q}|}=\frac{\eta_1}{\eta_2}$
$(B)$ $\frac{|\overrightarrow{V}_{P}|}{|\overrightarrow{V}_{Q}|}=\frac{\eta_2}{\eta_1}$
$(C)$ $\overrightarrow{V}_{P} \cdot \overrightarrow{V}_{Q} > 0$
$(D)$ $\overrightarrow{V}_{P} \cdot \overrightarrow{V}_{Q} < 0$

$A$ small sphere of mass $m$ is dropped from a great height. After it has fallen $100 \; m$,it has attained its terminal velocity and continues to fall at that speed. The work done by air friction against the sphere during the first $100 \; m$ of fall is

$A$ metal sphere of radius $R$ and density $\rho_1$ is dropped in a liquid of density $\sigma$ and moves with terminal velocity $V$. Another metal sphere of the same radius and density $\rho_2$ is dropped in the same liquid. Its terminal velocity will be:

The speed of a ball of radius $2 \,cm$ in a viscous liquid is $20 \,cm / s$. What will be the speed of a ball of radius $1 \,cm$ in the same liquid (in $\,cm / s$)?

In Millikan's oil drop experiment,what is the terminal speed of an uncharged drop of radius $2.0 \times 10^{-5} \; m$ and density $1.2 \times 10^{3} \; kg \; m^{-3}$? Take the viscosity of air at the temperature of the experiment to be $1.8 \times 10^{-5} \; Pa \; s$. How much is the viscous force on the drop at that speed? Neglect buoyancy of the drop due to air.