Internal Loadings. Resultant Force and Moment. Coplanar Loadings. Stress. Stress Derivation. A very small finite force ?F is acting on an associated area ?A.Replace this force with its directional components, ?Fx, ?Fy, and ?Fz. Take the limit as ?A approaches zero of the quotient of the component forces and the areasThis quotient is called, stress. It represents the intensity of the force on a specified plane..