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+--- Thread: Buoyancy — Why Things Float Upward (/showthread.php?tid=422)
Buoyancy — Why Things Float Upward - Leejohnston - 01-08-2026
## Buoyancy — Why Things Float Upward
### 1. The Equation
Buoyant force:
F_b = ρ × g × V
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### 2. What Each Symbol Means
- F_b = buoyant force
- ρ = density of the fluid
- g = gravitational acceleration
- V = volume of fluid displaced
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### 3. What the Equation Is Telling Us
An object submerged in a fluid experiences an **upward force** equal to the weight of the fluid it displaces.
Floating is about **displacement**, not weight alone.
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### 4. Where It Comes From (Intuition)
Pressure increases with depth.
The bottom of an object experiences more pressure than the top, creating a net upward force.
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### 5. Worked Example
If an object displaces:
- 0.02 m³ of water
- water density ≈ 1000 kg/m³
F_b = 1000 × 9.8 × 0.02
= **196 newtons**
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### 6. Real-World Applications
- Ships and submarines
- Hot air balloons
- Hydrometers
- Human buoyancy in water
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### 7. Common Misconceptions
- Heavy objects always sink → false
- Shape alone determines floating → false
- Buoyancy only applies in water → false
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### Try It Yourself
Why does a massive steel ship float while a small steel ball sinks?