Lift: Bernoulli’s Principle


Find out how Bernoulli's principle helps explain lift.


Hi, my name is Jamila. I'm an Explainer at the National Air and Space Museum's "How Things Fly" gallery, and today I'm going to talk to you about lift.

I'm standing in front the Spirit of St. Louis airplane. It was flown in 1927 by Charles Lindbergh and it was the first successful solo flight over the Atlantic Ocean. Now, how was this plane able to generate lift? How was it able to stay in the air?

Now, I can explain that using this airfoil here. An airfoil is like a cutout or a cross section of a wing. So, if I were to take a wing and slice it into pieces, like a loaf of bread, this would be one slice of the wing.

Now, if we compare this airfoil to the Spirit of St. Louis we'll notice they have very similar shapes. They have curved tops and flat bottoms. An airplane's wing will be shaped this way because of something called Bernoulli's Principle.

Daniel Bernoulli was a Swiss mathematician who studied the movement of fluids, like air and water, and he realized that a faster moving fluid will have a lower pressure, while a slower moving fluid has a higher pressure.

Now, let's apply this to our airfoil, or to a wing, so that when the plane starts flying and air hits the wing you're going to get faster moving air on top, it's going to speed up, because of the curve. At the bottom, where it's flat, you're gonna have a slower moving air. It's not going to be as fast as the air on top. That slower air is high air pressure, and the faster air is low air pressure. That high air pressure pushes up on the airfoil, or up on the wing, and that's why something as heavy as an airplane can fly.

Don't believe me well I have experiment we all can try at home with a single sheet of paper. If I were to place this paper beneath my lips and blow, would it go up or would it go down? Let's see what happens.

We noticed that the paper goes up, and the reason why is because of Bernoulli's Principle. When I blew my fast air on top of the sheet of paper, it was a lower pressure than all the air in the room. Because the air in the room is slower than the air that I was blowing. So, that high air pressure works from beneath, and it pushes up on our sheet of paper. And the same thing is happening to an airplane's wing. And that's why something as heavy as an airplane, like the Spirit of St. Louis is able to generate lift.

Categories: Aerodynamics