Question

.Calculate the viscous force acting on a rain drop of diameter 4mm,

Falling with a uniform velocity 2m/s through air. The coefficient of

Viscosity of air is 2.8 x 10-5 Ns/m2

S h r e e G a​

Answer 1

i have solved the question in the pic i attached below, hope it helps you!

Answer 2

Given : Rain drop of diameter 4mm,

             Falling with a uniform velocity 2m/s.

To Find : Viscous force acting on a rain drop.

Solution :

Diameter of Rain Drop = 4mm = 0.004 m

Radius of Rain drop = d/2 = 0.002 m.

Rain Drop falling with uniform velocity = 2m/s.

$\[Viscosity{\text{ }}of{\text{ }}air{\text{ }}is{\text{ }}2.8{\text{ }} \times {\text{ }}{10^{ - 5}}Ns/{m^2}\]$ is given.

By Stroke's Law, the viscous force on the raindrop is

$\[{F_{Viscous}} = 6\pi \eta r{v_0}\]$

Where,

$\[\eta \]$= Viscosity of air

$\[{v_0}\]$ = Rain Drop falling with uniform velocity

r = Radius of Rain drop

By Putting Value in Stroke's Law equation

$\[{F_{Viscous}} = 6 \times 3.14 \times (2.8 \times {10^{ - 5}} \times 0.002) \times 2\]$

$\[{F_{Viscous}} = 211.008 \times {10^{ - 8}}N\]$

Hence, Viscous force acting on rain drop is $\[211 \times {10^{ - 8}}N\]$.