$A$ 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 terminal velocity of a metallic ball of radius $6 \ mm$ in a viscous fluid is $20 \ cm/s$. The terminal velocity of another ball of same material and having radius $3 \ mm$ in the same fluid will be . . . . . . $cm/s$.

Eight spherical rain drops of the same mass and radius are falling down with a terminal speed of $6 \ cm \ s^{-1}$. If they coalesce to form one big drop,what will be the terminal speed of the bigger drop (in $cm \ s^{-1}$)? (Neglect the buoyancy of the air)

Two uniform solid balls of same density and of radii $r$ and $2r$ are dropped in air and fall vertically downwards. The terminal velocity of the ball with radius $r$ is $1 \, cm \, s^{-1}$. Find the terminal velocity of the ball of radius $2r$ (neglect buoyant force on the balls). ........... $cm \, s^{-1}$

Suppose the average mass of raindrops is $3.0 \times 10^{-5} \ kg$ and their average terminal velocity is $9 \ m/s$. Calculate the energy transferred by rain to each square metre of the surface at a place which receives $100 \ cm$ of rain in a year.

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: