Question

3. A rain drop of radius 0.3mm has terminal velocity in air = 1m/s. The viscosity of air is 18x 10-5 poise. The viscous force on it is: * O 101.73 x 10-4 dyne O 101.73x10-5 dyne O 16.95 x 10-4 dyne O 16.95 x 10-5 dyne​

Answer 1

Radius of drop r = 0.3 mm = 0.03 cm

Terminal velocity vc = 1 m/S = 100 cm/s

Viscosity of air η = 18 × 10^-3 poise

Viscous force F=6πηr vc

∴ F= 6π×18×10^−3×0.03×100

= 1.0178 dyne (ans.)