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+--- Thread: Density — Why Things Float or Sink (/showthread.php?tid=420)
Density — Why Things Float or Sink - Leejohnston - 01-08-2026
## Density — Why Things Float or Sink
### 1. The Equation
Density = Mass ÷ Volume
ρ = m ÷ V
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### 2. What Each Symbol Means
- ρ = density
- m = mass
- V = volume
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### 3. What the Equation Is Telling Us
Density describes **how tightly matter is packed**.
Objects float if their density is lower than the fluid they’re in.
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### 4. Where It Comes From (Intuition)
A heavy object can float if it spreads its mass over a large volume.
That’s why ships float but solid steel sinks.
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### 5. Worked Example
If:
- mass = 2 kg
- volume = 0.004 m³
Density = 2 ÷ 0.004
= **500 kg/m³**
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### 6. Real-World Applications
- Ships and submarines
- Hot air balloons
- Oil floating on water
- Planetary science
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### 7. Common Misconceptions
- Heavy things sink → false
- Floating depends on shape alone → false
- Density never changes → false
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### Try It Yourself
Why does ice float on water even though it’s solid?