A rain drop of radius 0.3mm has terminal velocity 1m/s in air. The viscosity of air is 18X10-5 poise, then viscous force is​

F = 1.0178 × 10^(-2) dyne

Explanation:

From stokes law, the viscous force also known as drag force on rain drop is given by the formula;

F = 6πηrv

Where;

η is viscosity

r is radius

v is velocity

We are given;

η = 18 × 10^(-5) poise

r = 0.3 mm = 0.03 cm

v = 1 m/s = 100 cm/s

Thus;

F = 6π × 18 × 10^(-5) × 0.03 × 100

F = 1.0178 × 10^(-2) dyne

when a device is used in a circuit in which the voltage is 81 v, the current flowing through the device is 3 a. what is the resistance of the device?

a. 27 ω

b. 40.5 a

c. 243 ω

d. 243 a

the correct answer is a. 27