Thinking in terms of the conservation of energy, it seems to make sense that if you took a relatively elastic rod with hooks on either end, so that it could be bent all the way around and made to hook to itself (and make a loop), that the energy required to bend it into a closed loop would be put into the rod. So essentially the work done in bending the rod into a loop would be found in the rod after the act of bending it into a loop (and hooking it to itself) was over? And that same energy would be released when the loop was unhooked and allowed to return to its natural straight length again? Does anyone know what formula one would use to determine the energy required to bend a rod of a given elasticity into a loop? Of course, keeping it as a loop of course is another question entirely that I'm not as concerned with. Thanks for any help or guidance.