In an experiment,a small steel ball falls through a liquid at a constant speed of $10\, cm/s$. If the steel ball is pulled upward with a force equal to twice its effective weight,how fast will it move upward? ......... $cm/s$

$A$ small metallic sphere of diameter $2 \ mm$ and density $10.5 \ g/cm^3$ is dropped in glycerine having viscosity $10 \ \text{Poise}$ and density $1.5 \ g/cm^3$. The terminal velocity attained by the sphere is . . . . . . $cm/s$. $(\pi = \frac{22}{7}$ and $g = 10 \ m/s^2)$

$n$ small drops of the same size fall through air with a constant terminal velocity of $5 \ cm/s$. If they coalesce to form a single big drop,what is the terminal velocity of the big drop?

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.

$A$ small rigid spherical ball of mass $M$ is dropped in a long vertical tube containing glycerine. The velocity of the ball becomes constant after some time. If the density of glycerine is half of the density of the ball,then the viscous force acting on the ball will be (consider $g$ as acceleration due to gravity).

Two spheres of the same material,but of radii $R$ and $3R$ are allowed to fall vertically downwards through a liquid of density $\rho$. The ratio of their terminal velocities is