Answer:
Explanation:
First we should recall how Newton's laws relates shear stress to a fluid's velocity profile:

where tau is the shear stress, mu is viscosity, v is the fluid's velocity and y is the direction perpendicular to flow.
Now, in this case we have a parabolic velocity profile, and also we know that the fluid's velocity is zero at the boundary (no-slip condition) and that the vertex (maximum) is at  and the velocity at that point is
 and the velocity at that point is 
We can put that in mathematical terms as:

From the no-slip condition, we can deduce that  and so we are left with just two terms:
 and so we are left with just two terms:

We know that the vertex is at  and so we can rewrite the last equation as:
 and so we can rewrite the last equation as:

where k and h are constants to be determined. First we check that  :
 :

So we found that h was the maximum velocity for the fluid, now we have to determine k, for that we need to make use of the no-slip condition.

And thus we find that the final expression for the fluid's velocity is:

where v is in mm/s and y is in mm.
In SI units it would be:

To calculate the shear stress, we need to take the derivative of this expression and multiply by the fluid's viscosity:


for  we have:
 we have:

Which is our final result