Crude oil, with specific gravity SG=0.85 and viscosityμ = 2.15×10−3 lbf sec/ft2, flows steadily down a surfaceinclined θ = 30 degrees below the horizontal in a film ofthickness h=0.125 in. The velocity profile is given by u =ρg/μ(hy − y2/2)sinθ
(Coordinate x is along the surface and y is normal to thesurface.) Plot the velocity profile. Determine the magnitude anddirection of the shear stress that acts on the surface.