An air bubble of $1\, cm$ radius is rising at a steady rate of $2.00\, mm/sec$ through a liquid of density $1.5\, g/cm^3$. Neglect the density of air. If $g = 1000\, cm/sec^2$,then the coefficient of viscosity of the liquid is:

In the experiment for measurement of viscosity $\eta$ of a given liquid with a ball having radius $R$,consider the following statements.
$A.$ Graph between terminal velocity $V$ and $R$ will be a parabola.
$B.$ The terminal velocities of different diameter balls are constant for a given liquid.
$C.$ Measurement of terminal velocity is dependent on the temperature.
$D.$ This experiment can be utilized to assess the density of a given liquid.
$E.$ If balls are dropped with some initial speed,the value of $\eta$ will change.
Choose the correct answer from the options given below:

The terminal velocity of a copper ball of radius $2.0 \; mm$ falling through a tank of oil at $20 \; ^{\circ}C$ is $6.5 \; cm \; s^{-1}$. Compute the viscosity of the oil at $20 \; ^{\circ}C$. Density of oil is $1.5 \times 10^{3} \; kg \; m^{-3}$,density of copper is $8.9 \times 10^{3} \; kg \; m^{-3}$.

Two solid spheres of radii $2 \ mm$ and $4 \ mm$ are tied to the two ends of a light string and released in a liquid of specific gravity $1.3$ and coefficient of viscosity $1 \ Pa \cdot s$. The string is just taut when the two spheres are completely submerged in the liquid. If the density of the materials of the two spheres is $2800 \ kg \cdot m^{-3}$,then the terminal velocity of the system of the spheres is (take $g = 10 \ m \cdot s^{-2}$):

$125$ small water drops of same size fall through air with constant terminal velocity $4 \,cm/s$. They coalesce to form a big drop. The terminal velocity of the big drop is: (in $\,m/s$)

Two spheres of the same material, but of radii $R$ and $3R$ are allowed to fall vertically downwards through a liquid of density $\rho$. The ratio of their terminal velocities is