Problem $4$:

The long bolt passes through the $\backslash (30-\backslash$mathrm$\{$mm$\}\backslash )-$thick plate. If the force in the bolt shank is $8$ kN $,$ determine the average normal stress in the shank, the average shear stress along the cylindrical area of the plate defined by the section lines $\backslash ($ a$-$a $\backslash ),$ and the average shear stress in the bolt head along the cylindrical area defined by the section lines $\backslash (\backslash$mathrm$\{$b$\}-\backslash$mathrm$\{$b$\}\backslash )$