Consider two rigid bars of equal length, AB and BC, connected to each other and a spring of constant k connected to point B. What will be the magnitude of the critical load for this system if load F is applied vertically downwards at point A? The bar gets deflected by a small angle due to the applied load, resulting in elongation X in the spring. The free-body diagram for both bars is drawn, and the force equilibrium equation is applied for the horizontal direction. Considering the bar AB separately, the equilibrium equation for the moment of forces is applied at point B. Solving this equation gives the support reaction at point A. Similarly, applying the equilibrium of the moment of forces at point B again gives the support reaction at point C. Substituting the reaction supports at points A and B into the force equilibrium equation gives the total spring force balancing the two reaction supports. Here, the elongation of the spring cannot be zero, yielding the corresponding critical load value for the given system.