Consider a beam subjected to transverse loading.
The bending moment M(x) produced in the beam by the transverse loads creates normal stress σ that is distributed over the cross section.
The transverse loads also produce transverse shear force V(x) in the beam. The transverse shear force V(x) is the resultant of the shear stress τ that is distributed over the cross section.
We will derive an equation that relates the transverse shear force V to the shear stress τ that is produced in the beam.