Not quite any physics questions. Feynman imposed a rule that he would "not take any question the answer to which did not match the impedance of your knowledge.

Not quite any physics questions. Feynman imposed a rule that he would "not take any question the answer to which did not match the impedance of your knowledge." So a freshman asking "What is quantum chromodynamics?" was gently nudged into a simpler answer that they might learn something from.