The next time you plan to make paper airplanes with the kids, throw in this little STEM exercise, first!
The idea is to hold a piece of paper (loosely from the top two corners) at about level with your chin, curling the paper slightly toward you at the top. Then blow down as hard as you can. Before we actually did the exercise, I challenged Travis to write down his hypothesis (fancy word!): Would his breath blow the paper down toward his chest, or up toward his nose?
His guess, surprising me because it is counter to logic, was… Up!
Well, it turns out he was right ,and the answer is thanks to some neat science. When the molecules above the paper move faster from your breath, the air pressure is becomes lower. That means the higher pressure air under the paper pushes it upward. So the paper billows up instead of down!
The same principal can be applied to the wing of an airplane, hence all this science before we got around to making our paper planes. Of course the next thing we did was to fold up lots of paper planes to soar all around the house!