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The elastic limit of brass is 379 MPa. What should be the minimum diameter of a brass rod if it is to support a 400 N load without exceeding its elastic limit?

1. 1.16 mm
2. 1.36 mm
3. 1.00 mm
4. 0.90 mm

Correct answer: 1.16 mm

Solution

Stress = F/(pi d^2/4) <= 379e6 Pa. d^2 >= 4*400/(pi*379e6) = 1.34e-6, so d >= 1.16e-3 m = 1.16 mm (minimum diameter).

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