The following equation i came across when i was studying the minimum potential energy principle QUOTE: POTENTIAL ENERGY OF AN ELASTIC BODY(example spring)=STRAIN ENERGY-POTENTIAL ENERGY OF LOADING We all know that the strain energy of a spring is equal to 0.5*k*x*x were x is the displacement in the spring and k is the spring constant. This is called STRAIN ENERGY. What is the second term "POTENTIAL ENERGY OF LOADING" mean. Only mass and elastic bodies can store energy. Why LOADING has POTENTIAL ENERGY? Any examples/webs?