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

Eight identical small drops of water are falling down vertically through a medium,each with terminal velocity $v$. If they combine to form a single drop,then its terminal velocity will be (in $v$)

$A$ 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?

$A$ sphere is dropped under gravity through a fluid of viscosity $\eta$. If the average acceleration is half of the initial acceleration,the time to attain the terminal velocity is ($\rho$ = density of sphere; $r$ = radius).

Two rain drops of same radius $r$ falling with terminal velocity $V$ merge and form a bigger drop with radius $R$. The terminal velocity of the bigger drop is:

The average mass of rain drops 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.