The graph between terminal velocity (along $y-$ axis) and square of radius (along $x-$ axis) of a spherical body of density $\rho$ allowed to fall through a fluid of density $\sigma$ is a

$A$ water drop of radius $1\,\mu m$ falls in a situation where the effect of buoyant force is negligible. The coefficient of viscosity of air is $1.8 \times 10^{-5}\,Nsm^{-2}$ and its density is negligible as compared to that of water $10^{3}\,kgm^{-3}$. The terminal velocity of the water drop is . . . . . . $\times 10^{-6}\,ms^{-1}$. (Take acceleration due to gravity $= 10\,ms^{-2}$)

Give the practical uses of viscosity.

$A$ small spherical solid ball is dropped in a viscous liquid. Its journey in the liquid is best described by which curve in the figure?

Two rain drops of same radius are falling through air each with a steady speed of $5 \,cm/s$. If the drops coalesce,the new steady velocity of the big drop will be

Which of the following graphs best represents the motion of a raindrop?