Question

A rain drop of radius 0.3mm falls through air with a terminal velocity of 1m/s . The viscosity of air is 18*10 find the viscous force on the rain drop?

Answer 1

Explanation:

Here, r=0.3mm=0.03cm,

v=1ms

−1

=100cms

−1

,

η=18×10

−5

poise.

According to stokes law, force of viscosity on rain drop is

F=6πηrv

=6×3.142×18×10

−5

×0.03×100 dyne

=1.018×10

−3

dyne.

Answer 2

Answer:

r = 0.3mm = 0.03cm

Vt = 1m/s = 100cm/s

n(eta) = 18x10^-5poise

By stokes law,

Fv = 6πnrVt

= 6×22/7×18×10^-5×0.03×100

= 2376/7×10^-5×3

= 7128/7×10^-5

= 1018.28×10^-5

= 1.01×10^-2 dyne