Physics | VITEEE 2019 | Discussion Page

A raindrop of radius 0.3 mm has a terminal velocity in air is 1 m/s. The viscosity of air is 8 x 10^-5 poise. The viscous force on it is

$45.2\times 10^{-4}$ dyne

$101.73\times 10^{-5}$ dyne

$16.95\times 10^{-4}$ dyne

$16.95\times 10^{-5}$ dyne

Option A

Radius of drop, r = 0.3 mm = 0.03 cm

Terminal velocity v = 1 m/s = 100 cm/sec

Viscosity of air, η = 8 x 10^-5 poise

Viscous force, f = 6 πηrv

F = 6 x 3.14 × (8 ×10^-5) x 0.03 x 100 = 4.52 x10^-3 dyne

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