Sixty-four spherical rain drops of equal size are falling vertically through air with a terminal velocity of $1.5 \ m/s$. All of the drops coalesce to form a single big spherical drop. The terminal velocity of the big drop is ........... $m/s$.

$n$ small drops of the same size fall through air with a constant terminal velocity of $5 \ cm/s$. If they coalesce to form a single big drop,what is the terminal velocity of the big drop?

Two small spherical metal balls,having equal masses,are made from materials of densities $\rho_{1}$ and $\rho_{2}$ (where $\rho_{1} = 8 \rho_{2}$) and have radii of $1 \; mm$ and $2 \; mm$,respectively. They are made to fall vertically (from rest) in a viscous medium whose coefficient of viscosity equals $\eta$ and whose density is $0.1 \rho_{2}$. The ratio of their terminal velocities would be:

Two raindrops reach the earth with different terminal velocities having the ratio $9: 4$. The ratio of their volumes is

The terminal velocity of a small sphere of radius $a$ in a viscous liquid is proportional to

$A$ small metallic sphere of diameter $2 \ mm$ and density $10.5 \ g/cm^3$ is dropped in glycerine having viscosity $10 \ \text{Poise}$ and density $1.5 \ g/cm^3$. The terminal velocity attained by the sphere is . . . . . . $cm/s$. $(\pi = \frac{22}{7}$ and $g = 10 \ m/s^2)$