I did a Bernoulli demo.

Wearing a pilot suit; some kids interested, some bored.

Started by having them all get a #2 pencil and a sheet of paper. Showed them how to hold it, with the paper curled around the top-side of a horizontal pencil.

So I ask several kids at random: "What will happen if you blow on the top of the paper?"

Predictably, they all said "It will go down." There seemed to be a lot of implied "Duh!" cynicism in their response.

"Try it," I said.

They did, and the look of amazement on their faces when it went UP was priceless. The teacher, too.

I had their rapt attention for the next 45 minutes. Some of them kept blowing on that "wing" the entire time, trying to figure out why it was so.

That was a fun day.