What does Bernoulli's principle say?
The Bernoulli equation, P + ½ρv² + ρgh = constant, expresses conservation of energy in a flowing fluid. At the same height, if speed v goes up, pressure P must go down. Pinch a garden hose and the water speeds up; blow between two sheets of paper and they're pulled together rather than apart.
Do airplanes really fly because of Bernoulli?
Air does move faster over the top of a wing, lowering pressure there, and that difference contributes to lift. But the popular "equal transit time" story—that air on top must meet air below at the trailing edge—is wrong. A complete explanation also includes the wing deflecting air downward (Newton's third law). Similar effects show up in spray bottles, carburetors, and curving soccer balls (the Magnus effect).
FAQ
- When does Bernoulli's equation hold?
- Along a streamline in steady, incompressible flow with negligible viscosity.
- Is the clingy shower curtain the same effect?
- Partly—airflow and swirling from the spray lower the pressure inside the curtain.
Sources reviewed: 2026-10-25
References
- Bernoulli, D. (1738). Hydrodynamica.
- Anderson, J. D. (2016). Fundamentals of Aerodynamics (6th ed.). McGraw-Hill.
- Babinsky, H. (2003). How do wings work? Physics Education, 38(6), 497–503.