Find the stored energy in a capacitor using force between the plates.

Explanation

To find the stored energy in a capacitor using the force between the plates, we can follow these steps:

### Step-by-Step Solution:

1. **Define the Capacitor Configuration**:
- Consider a parallel plate capacitor with plate area \( A \), plate separation \( d \), and charge \( q \) on the plates.

2. **Calculate Charge Density**:
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