As an analogy, consider a traffic jam caused by road construction which takes two lanes down to one. Note: Perhaps counterintuitively, the pressure is greater in the wider section with the lower fluid velocity. Which pipe feels a greater pressure from the fluid? (Assume they are on level ground.)īy continuity, A 1 v 1 = A 2 v 2 A_1 v_1 = A_2 v_2 A 1 v 1 = A 2 v 2 . P A 1 2 ρ v A 2 ρ g h A = P B 1 2 ρ v B 2 ρ g h B P_A \frac12 \rho v_A^2 \rho gh_A = P_B \frac12 \rho v_B^2 \rho gh_B P A 2 1 ρ v A 2 ρ g h A = P B 2 1 ρ v B 2 ρ g h B įluid flows from one pipe into a second of smaller cross-sectional area. In both cases, the density of the fluid provides a "default" closeness of the particles in the fluid, so density is incorporated into the principle as well. The other is the idea that as the amount of fluid above decreases, the particles will be less compacted, thus exhibiting less apparent pressure. One is the idea that if a fluid moves faster, the individual particles will spread out more, decreasing the pressure on the surroundings. Louis is able to generate lift.Bernoulli's principle actually relates pressure to two separate phenomena. And that's why something as heavy as an airplane, like the Spirit of St. And the same thing is happening to an airplane's wing. So, that high air pressure works from beneath, and it pushes up on our sheet of paper. Because the air in the room is slower than the air that I was blowing. 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. We noticed that the paper goes up, and the reason why is because of Bernoulli's Principle. 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. 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.ĭon't believe me well I have experiment we all can try at home with a single sheet of paper. That slower air is high air pressure, and the faster air is low air pressure. It's not going to be as fast as the air on top. At the bottom, where it's flat, you're gonna have a slower moving air. 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. An airplane's wing will be shaped this way because of something called Bernoulli's Principle.ĭaniel 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. Louis we'll notice they have very similar shapes. Now, if we compare this airfoil to the Spirit of St. 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. An airfoil is like a cutout or a cross section of a wing. Now, I can explain that using this airfoil here. Now, how was this plane able to generate lift? How was it able to stay in the air? It was flown in 1927 by Charles Lindbergh and it was the first successful solo flight over the Atlantic Ocean. 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. Find out how Bernoulli's principle helps explain lift.
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