Question

Two horizontal plates placed 250mm have an oil of viscosity 20 poises. Calculate the shear stress in oil if upper plate is moved with velocity of 1250mm/s.

(a) 20 N/m^2

(b) 2 N/m^2

(c) 10 N/m^2

(d) None of the mentioned

This question was addressed to me in an online quiz.

I'm obligated to ask this question of Viscosity in section Properties of Fluids of Fluid Mechanics

Answer 1

Correct answer is (c) 10 N/m^2

Explanation: Shear Stress = Viscosity * Velocity Gradient

                                           = 20/10* 1.25/0.25

                                           = 10 N/m^2.