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A wire is fixed at one end and stretches by length ℓ by applying a force F. The work done in stretching is

1. 2Fℓ
2. Fℓ
3. F/2
4. Fℓ/2

Correct answer: Fℓ/2

Solution

The work done in stretching the wire is calculated as the average force applied over the distance stretched. Since the force increases linearly from 0 to F as the wire stretches by length ℓ, the average force is F/2, resulting in the work done being Fℓ/2.

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