[Leejohnston]

## 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?