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Two identical wires A and B of the same material are loaded as shown. If the elongation of wire B is 1.5 mm, what is the elongation of wire A? (Neglect the masses of the wires.)

1. 0.5 mm
2. 1.0 mm
3. 1.5 mm
4. 3.0 mm

Correct answer: 1.0 mm

Solution

For identical wires, elongation is proportional to tension; the loading gives wire A a tension 2/3 that of B, so its elongation is (2/3)*1.5 = 1.0 mm.

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