Hi. The Lagrange equations can be derived simply by using Newton's laws and defining potential, work and kinetic energy. So that's just a mathematical reformulation of known results. Is it the same with Hamilton's principle? Is the concept of "action" and it being stationary just another mathematical reformulation from Newton's laws, or is it something else? Because Hamilton's principle leads to the Langrange equations just the same as newton's laws. My professor did not discuss this. He simply presented Hamilton's principle as a postulate and left it at that. PS: What is up with this "generalized force" thing? I don't exactly understand what that is all about. Would appreciate it if somebody could explain briefly.