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In a careful experiment, a wire is stretched by equal outward forces at its two ends and the resulting elongation is measured. If the applied force is then exactly doubled while the wire is still elastic but now operates beyond the proportional (linear) limit, the change in length of the wire:

1. will exactly double
2. will be slightly more than double
3. will be slightly less than double
4. will decrease by exactly a factor of two

Correct answer: will be slightly more than double

Solution

Past the proportional limit the curve bends toward the strain axis, so doubling the force gives somewhat more than double the elongation.

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