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+--- Thread: Momentum — Why Crashes Are Dangerous (/showthread.php?tid=416)
Momentum — Why Crashes Are Dangerous - Leejohnston - 01-08-2026
## Momentum — Why Crashes Are Dangerous
### 1. The Equation
Momentum = mass × velocity
p = mv
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### 2. What Each Symbol Means
- p = momentum
- m = mass
- v = velocity
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### 3. What the Equation Is Telling Us
Momentum measures **how hard something is to stop**.
More mass or more speed means more momentum.
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### 4. Where It Comes From (Intuition)
Stopping momentum requires force over time.
That’s why airbags and crumple zones save lives.
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### 5. Worked Example
If:
- mass = 1,000 kg
- speed = 20 m/s
p = 1,000 × 20
= **20,000 kg·m/s**
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### 6. Real-World Applications
- Vehicle safety
- Sports collisions
- Space docking
- Ballistics
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### 7. Common Misconceptions
- Momentum and force are the same → false
- Heavier objects always cause more damage → false
- Speed matters more than mass → incomplete
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### Try It Yourself
What happens to momentum if speed doubles?