Let the expression for the strain energy U for a simply supported leaf spring with load P...

Let the expression for the strain energy U for a simply supported leaf spring with load P in the center be given by 1/2Py, where y is the deflection. Prove that stress , where c is the distance from the neutral axis to the edge of the cross section. Use this relationship to prove that for a rectangular cross section the energy absorbed for a constant stress σ is the same, regardless of whether the long or short dimension is vertical.