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 ........... $m/s$.

$A$ small steel sphere of mass $m$ is falling vertically through a viscous liquid with a constant speed $v$. Which row in the table correctly describes the changes with time in the kinetic energy and gravitational potential energy of the sphere?

On which factors does terminal velocity depend? Explain.

$A$ large drop of oil (density $0.8 \, g/cm^3$ and viscosity $\eta_0$) floats up through a column of another liquid (density $1.2 \, g/cm^3$ and viscosity $\eta_L$). Assuming that the two liquids do not mix,the velocity with which the oil drop rises will depend on.

An air bubble of $1\, cm$ radius is rising at a steady rate of $2.00\, mm/sec$ through a liquid of density $1.5\, g/cm^3$. Neglect the density of air. If $g = 1000\, cm/sec^2$,then the coefficient of viscosity of the liquid is:

If the terminal speed of a sphere $A$ [density $\rho_A = 7.5 \ kg \ m^{-3}$] is $0.4 \ ms^{-1}$ in a viscous liquid [density $\rho_L = 1.5 \ kg \ m^{-3}$],the terminal speed of sphere $B$ [density $\rho_B = 3 \ kg \ m^{-3}$] of the same size in the same liquid is: (in $ms^{-1}$)