Solve Prob. 11-56 using the principle of potential energy. Investigate the stability of the rod when it is in the equilibrium position.
Prob. 11-56
The uniform rod AB has a weight of 10 lb. If the spring DC is unstretched when θ =0° , determine the angle for equilibrium using the principle of virtual work. The spring always remains in the horizontal position due to the roller guide at D.