Answer:
Average shear stress;τ = 80 Pa
Explanation:
We are given;
Thickness;t = 5mm = 0.005 m
Velocity;u = 4 m/s
Specific Gravity;Sg = 0.8
Kinematic viscosity;ν = 1.25 × 10^(-4) m²/s
We are not given density of the oil, but given specific gravity of 0.8. we know that formula for specific gravity of an object = Density of object/Density of water
Density of water = 1000 kg/m³
Thus;
0.8 = density of oil/1000
Density of oil = 800 kg/m³
Now, let's calculate dynamic viscosity of the oil. It's given by the formula;
μ = ρν
Where;
μ is dynamic viscosity
ρ is density of oil
ν is kinematic viscosity
So,
μ = 800 × 1.25 × 10^(-4)
μ = 0.1 kg/m.s
Now, formula for the average shear stress is given as;
τ = μ × u/t
Plugging in the relevant values, we have;
τ = 0.1 × 4/0.005
τ = 80 Pa