A rain drop of radius 0.3 mm has a terminal velocity in `"air" = 1 "m/s"`. The viscosity of air is `8 xx 10^(–5)` poise. The viscous force on it is

Options

A. `45.2 xx 10 ^(-4)` dyne
B. `101. 73xx 10 ^(-5)1` dyne
C. `16.95 xx 10 ^(-4)` dyne
D. `16.96 xx 10 ^(-5)` dyne

Answer

A

Explanation

`F = 4 pi eta r v = 6 xx 3.14 xx (8 xx 10 ^(-5)) xx 0.03 xx 100= 4.52 xx 10 ^(-3) ` dyne