How to work out the mean shear stress I section beam

[cjdfromclm]

I have completed bending moment and shear force diagrams and have a question asking for the mean shear stress. I know this is worked out using the formula: tau = F/A.

I am unsure of what force to use is it the max shear force on my diagram? My other thought is that it could be an avergae of all the shear force acting along the beam??

Thanks in advance

Chris

 

[PhanthomJay]

I Believe they are looking for the average shear stress at the point of max shear . The shear stress is not uniform across the cross section. It's variation can be calculated , but for now, what is the average shear stress in the web at max shear?

 

[cjdfromclm]

Thanks ill go with that :-)