Question

Calculate the viscous force on a ball of radius 1mm moving through a liquid of viscosity 0.2 Nsm^-2 at a speed of 0.07 ms^-1

Answer 1

Radius of the ball (a) = 1mm = 1 × 10^-3 m 

Co-effecient of viscosity of liquid (η) = 0.2 Nsm^-2 

Speed of the ball (v) = 0.07 ms^-1 

According to Stoke’s law 

Viscous force F = 6 π η av 

= 6 × 3.14 × 1 × 10^-3 × 0.2 × 0.07

= 0.26376 × 10^-3 = 2.64 × 10^-4 N