Spring is here, sa-pring is here
Life is skittles and life is beer
I think the loveliest time of the year
Is the spring, I do, don’t you? ‘course you do
Where Does The Spring Potential Energy Come From?
I dare you to find a physics textbook that doesn’t talk about springs. They are everywhere.
Spring potential energy is deformation of EM fields in the atomic structure of the spring. Dissolve an elastically stretched or compressed spring in a calorimeter and get different enthalpies of solution vs. the relaxed spring. Elastically stress a glassy plastic spring then heat it compressed in a calorimeter, looking at the integral under Tg for instance, the enthalpy of transition. Anharmonic terms amplify at larger deformations, eventually leading to permanent distortion. Shape-memory alloys (Nitinol) demostrate the utility of knowledge and cleverness. I-beams are generally good enough.
The important question is how simple a model can be and still give quality predictions. It doesn’t have go be ab initio correct for field work, it just has to work. A first term organic student using MO theory will be a corpse by a large margin. His neighbor using execrable LCAO theory will get a fat four-point (at least until the Woodward-Hoffmann rules).
Crude maps are still pretty good. Crude GPS does not exist – as the EU and Russia discovered.