Physically Incorrect

Just to let you know I’ve added new sub-categories for the physics puzzles on this site - mechanics, electromagnetism, thermodynamics, music and audio and Fermi questions, to help you navigate and find puzzles that interest you. It seems that there’s an overwhelming majority of mechanics puzzles (I like ‘em) - I’ll definitely start filling up the other categories, now that I  see how unpopulated they seem!