$A$ ball rises to the surface at a constant velocity in a liquid whose density is $4$ times greater than that of the material of the ball. The ratio of the force of friction acting on the rising ball to its weight is

$A$ steel ball is dropped in a viscous liquid. The distance of the steel ball from the top of the liquid is shown in the graph below. The terminal velocity of the ball is closest to .......... $m/s$.

Two drops of equal radius are falling through air with a steady velocity of $5\,cm/s$. If the two drops coalesce,then its terminal velocity will be

$A$ small drop of water falls from rest through a large height $h$ in air; the final velocity is

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? (Neglect the buoyancy of the air)

When a body falls in air,the resistance of air depends to a great extent on the shape of the body. $3$ different shapes are given in the figure: $(1)$ Disc,$(2)$ Ball,and $(3)$ Cigar-shaped. Identify the combination of air resistances $(R_1, R_2, R_3)$ which truly represents the physical situation. (The cross-sectional areas are the same).