I find it very interesting trying to solve the 'classic' kind of physics problems. The ones that Euler, the Bernouillis and co. bandied about, I've come across: The shape of a hanging chain The shape of a hanging elastic string The brachistochrone (the shape of a wire such that a bead running along it gets from A to B in the shortest time possible in a gravitational potential) The elastica (shape of a toothpick being gently bent) Profile curve of a bubble film suspended between two identical rings Profile curve of a meniscus (water in a glass beaker sort of thing) The last one I created a thread on a while ago, and think I got to the bottom of it. Let me know if you get a solution. Wondered if anyone knew any other good ones. If not, have a crack at these, some of them are pretty tricky (and watch out - there's no general analytic solution to the elastica problem, so don't pull your hair out over it). Hope I've posted this in the right place. They're clearly not homework questions.