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Masses of 1 kg and 2 kg hang from the two ends of a metal wire passing over a frictionless pulley. The breaking stress of the metal is (40/(3*pi)) * 10⁶ N/m². Taking g = 10 m/s², what is the minimum radius of the wire so that it does not break?

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

Correct answer: 0.5 mm

Solution

The Atwood tension is 40/3 N; setting T/(pi r²) = breaking stress gives r = 0.5 mm.

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