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If a longitudinal strain x is produced in a wire of Young's modulus Y, the elastic potential energy stored per unit volume of the wire is:

1. Y x²
2. 2 Y x²
3. (1/2) Y² x
4. (1/2) Y x²

Correct answer: (1/2) Y x²

Solution

Energy per unit volume = (1/2)(Y x)(x) = (1/2) Y x².

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