We got an email from the people running SteelyKid’s summer camp asking for volunteers to speak at a career day sort of event early next week. I said “Sure, I can do that, and talk about the glamorous life of a physics professor and book author.” They said “Great, you’ll be talking to several groups, ranging from second-graders down to 3-4 year olds.”
That’s… not quite the audience I was expecting (the camp runs up through 5th grade or so). I don’t think they’re going to care all that much about physics research, so instead, I’ll probably say “My job is to teach people about science” and then show them some simple physics tricks that don’t need many props. I was thinking of showing how light and heavy objects fall at the same rate, maybe a center-of-mass trick (the “stand against a wall and try to pick an object off the floor” game), and possibly the elastic-collision trick where you drop a tennis ball on top of a basketball and it hits the ceiling. The theory being that simple demos involving things and/or people falling on the floor will wow them even if they don’t understand the science.
But this seems like a good topic for polling my wise and worldly readers. So, if you were going to talk to a bunch of little kids about physics, and wanted a single really simple demo (i.e., no fancy electronics, no liquid nitrogen or other expensive props) to show them, what would you do?