A rain drop of radius 0.3 mm falls through air with a terminal viscosity of `1 m s^(-1)`. The viscosity of air is `18 xx 10^(-5)` poise. The viscous force on the rain drop is

Explanation

Given, radius of drop =0.3 mm =0.03 cm
v=1m/s =100 cm/s
`eta=18 xx 10^(-5)"poise"`
Force of viscosity on the rain drop is
`F=6 pi eta rv`
`=6 xx 3.142 xx 18 xx 10^(-5) xx 0.03 xx 100" dyne"`
`=1.018 xx 10^(-2)"dyne"`