How does Bernoulli's principle keep airplanes in the air?
Bernoulli's principle. Yes, it's hard to understand, but it really is responsible for keeping aeroplanes in the sky. Now, every time I have done something with Bernoulli's principle, or looked it up on the internet, or found it in a book, they always have a little picture of an aeroplane flying through the sky. It shows the aeroplane in a cross-section, and it shows the wings, and the wings are shaped so that the air goes across the top of the wing faster than the bottom. The air is moving across the top of the wing, and Bernoulli said where there's moving air there's low pressure, so we have low pressure on top of the wing. Air on the bottom of the wing is not moving as fast, and that's high pressure. So, that actually gives the plane lift and keeps it in the sky. Now, to go along with that, we have this little demonstration. It's simply a pen or a pencil, and you tape a piece of paper on it, just like a 2-inch strip, and this is supposed to represent the aeroplane wing. Now, my breath blowing across the top is going to represent the air blowing across the top of the wing. So, I hold this to my mouth, and it's going to be below my mouth. I'm going to blow across here. Right here we have moving air, and moving air is low pressure. On the bottom of this "wing" is going to be high pressure, and so this should come up in the air. So if I do this... [He blows twice and the paper flutters up] Now, did you see how that lifted it up? Now, I'd really like to do this and show more people, but then, I'd need a bigger piece of paper and more air. A bigger piece of paper and more air. I wonder... bigger piece of paper, more air. [Wavy dissolve. Professor Gizmo is standing outside.] Let's see. Bigger piece of paper, more air. Bigger piece of paper, more air. [Professor Gizmo picks up a mechanical blower with a roll of toilet paper mounted in front.] Bigger piece of paper, more air. Ho, ho, ho! Let's try this! [Professor Gizmo flips the on-switch. The toilet paper streams high into the air. Professor Gizmo gives gleeful laugh.] Hoo-hoooo! Ohhhh! Ohhhh! Ho, ho! It works! It works! Alright! Yahh! It works! Yay!!
