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A wire hung vertically from its upper end is stretched by 1 mm when a 200 N weight is attached to its lower end. Find the elastic potential energy stored in the wire.

1. 0.2 J
2. 10 J
3. 20 J
4. 0.1 J

Correct answer: 0.1 J

Solution

The work stored equals half the product of the stretching force and the extension: U = 0.5 * 200 * 0.001 = 0.1 J.

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