You have to hand it to Richard Feynman. He had a way of not only making difficult physics concepts understandable, he could also make everyday phenomena interesting by posing and then answering questions that do not even occur to most of us or, if they do, to which we are likely to give a facile or wrong answer.
Maggie Koerth-Baker brings to my attention a video in which Feynman explains how it is that trains stay on their tracks. It was new to me and quite fascinating. Although when I taught mechanics I had explained about the need for a differential on the wheel axes of cars to enable them to make turns, I had never wondered as to why train wheel axles did not have them.
Now I know.