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+--- Thread: Bernoulli’s Equation — Why Airplanes Fly (/showthread.php?tid=426)
Bernoulli’s Equation — Why Airplanes Fly - Leejohnston - 01-08-2026
## Bernoulli’s Equation — Why Airplanes Fly
### 1. The Equation
P + ½ρv² + ρgh = constant
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### 2. What Each Symbol Means
- P = pressure
- ρ = fluid density
- v = fluid speed
- g = gravitational acceleration
- h = height
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### 3. What the Equation Is Telling Us
In a flowing fluid:
- higher speed → lower pressure
- lower speed → higher pressure
Energy is shared between pressure, motion, and height.
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### 4. Where It Comes From (Intuition)
A fluid has a fixed amount of energy along a streamline.
If it speeds up, pressure must drop to compensate.
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### 5. Worked Example
If air speeds up over a wing:
- pressure above drops
- pressure below remains higher
This pressure difference produces **lift**.
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### 6. Real-World Applications
- Aircraft wings
- Carburetors
- Venturi meters
- Weather systems
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### 7. Common Misconceptions
- Wings only work because of Bernoulli → false
- Faster air means stronger force automatically → incomplete
- Lift requires curved wings → false
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### Try It Yourself
Why does blowing between two hanging sheets pull them together?