The scary thing is when you think about the work (or, rather, the k-work, as Thomas Moore in his “Six Ideas” would call it, which I think is a good idea) done by static friction. At first blush, it seems obvious that static friction is doing negative k-work on the object… but that would then seem to make it have *less* energy at the bottom than it really does. The answer is what you had in twitter: static friction doesn’t do work because there’s no relative motion between the two surfaces for which there is static friction. It’s kind of annoying, as it breaks down a bit the model we use of “consider extended objects as particles”, and it makes things more subtle, but that is ultimately what’s going on. Kinetic friction would dissipate energy, but again to figure out the amount of k-work done, you’d have to use the dr or dr/dt of the surface that was moving relative to the other surface.

For every question there is an experiment