Question

The velocity distribution for flow over a plate is given by $u=0.5y-y^2$ where 'u' is the velocity in m/s at a distance 'y' meter above the plate. If the dynamic viscosity of the fluid $0.9N-s/m^2$, then what is the shear stress at 0.20 m from the boundary ?

• A. 0.9 N/$m^2$
• B. 1.9 N/$m^2$
• C. 2.25 N/$m^2$
• D. 0.09 N/$m^2$

Answer 1

The correct option is D 0.09 N/$m^2$

$\text{Shear stress,}\tau =\mu \frac{du}{dy}=\mu (0.5-2y)$
at y = 0.2 m
$\tau =0.9\times (0.5-2\times 0.2)=0.09N/m^2$