Two drops of same radius are falling through air with steady velocity of $v \ cm/s$. If the two drops coalesce,what would be the terminal velocity?

$A$ spherical solid ball of volume $V$ is made of a material of density $\rho_1$. It is falling through a liquid of density $\rho_2$ $(\rho_2 < \rho_1)$. Assume that the liquid applies a viscous force on the ball that is proportional to the square of its speed $v$,i.e.,$F_{viscous} = -kv^2$ $(k > 0)$. The terminal speed of the ball is:

$A$ lead sphere of mass $m$ falls with a terminal velocity $V$ in a viscous liquid. With what terminal velocity will another lead sphere of mass $8m$ fall in the same liquid?

Why do dust particles settle down on the floor in a closed room? Explain.

$A$ metal sphere of radius $R$ and density $\varrho_{1}$ moves with terminal velocity $v_{1}$ through a liquid of density $\sigma$. Another sphere of the same radius but of density $\varrho_{2}$ moves through the same liquid. Its terminal velocity will be:

$A$ spherical metal ball of radius $r$ falls through a viscous liquid with terminal velocity $V$. Another metal ball of the same material but of radius $\frac{r}{3}$ falls through the same liquid. What will be its terminal velocity?