Question

A rain drop of radius 0.4 mm has a terminal velocity in air 4 m/s. If the coefficient of viscosity of air is 1.8 x 10^-4 poise, the viscous drag on the rain drop will be ____________.

Options

• 0.014 dyne

• 0.02 dyne

• 0.034 dyne

• 0.054 dyne

Answer 1

A rain drop of radius 0.4 mm has a terminal velocity in air 4 m/s. If the coefficient of viscosity of air is 1.8 x 10^-4 poise, the viscous drag on the rain drop will be 0.054 dyne.

Explanation:

`"F" = 6pi  eta"rv"`

`= 6 xx 3.142 xx 1.8 xx 10^-4 xx 0.04 xx 400`

`= 0.054  "dyne"`