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A lift of mass 1000 kg hangs from a thick iron wire. If the maximum acceleration of the lift is 1.2 m/s² and the maximum allowable stress in the wire is 1.4 x 10⁸ N/m², what is the minimum diameter of the wire? (take g = 9.8 m/s²)

1. 10⁻² m
2. 10⁻⁴ m
3. 10⁻⁶ m
4. 0.5 x 10⁻² m

Correct answer: 10⁻² m

Solution

T = 1000(9.8 + 1.2) = 11000 N; the minimum area is T/stress, giving d about 1 x 10⁻² m.

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