Two rain drops falling through air have radii in the ratio $1: 2$. They will have terminal velocity in the ratio

An air bubble of diameter $6\,mm$ rises steadily through a solution of density $1750\,kg/m^3$ at the rate of $0.35\,cm/s$. The coefficient of viscosity of the solution (neglect density of air) is $..........\,Pa\cdot s$ (given,$g = 10\,m/s^2$).

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 identical drops of water are falling through air with steady velocity $V$. If the two drops coalesce to form a single drop,what is the new terminal velocity of the single drop?

$A$ copper ball of radius $r$ travels with a uniform speed $v$ in a viscous fluid. If the ball is changed with another ball of radius $2r$,then the new uniform speed will be

$1$ poiseuille $=$ .......... poise