[Leejohnston]

## Potential Energy — Stored Power

### 1. The Equation

Gravitational potential energy:

PE = mgh

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### 2. What Each Symbol Means

- PE = potential energy (joules)
- m = mass (kg)
- g = gravitational acceleration (≈ 9.8 m/s² on Earth)
- h = height above a reference point (metres)

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### 3. What the Equation Is Telling Us

Potential energy is **energy stored because of position**.

The higher an object is lifted, the more energy it stores.

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### 4. Where It Comes From (Intuition)

Lifting an object requires work.

That work doesn’t disappear — it becomes stored energy, ready to be released if the object falls.

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### 5. Worked Example

If:
- m = 10 kg
- h = 5 m

PE = 10 × 9.8 × 5
= **490 joules**

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### 6. Real-World Applications

- Hydroelectric dams
- Roller coasters
- Lifting systems
- Falling objects

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### 7. Common Misconceptions

- Energy disappears when nothing moves → false
- Height is absolute → false (reference matters)
- Only heavy objects have potential energy → false

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### Try It Yourself

What happens to potential energy if:
- height doubles?
- mass halves?