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Question:

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?

1.16mm

1.00mm

0.90mm

1.36mm

Solution:

F/A = stress
400/(πd²/4) = 379 × 10⁶
d² = 1600/(π × 379 × 10⁶)
d² = 1.34 × 10⁻⁶
d = √(1.34 × 10⁻⁶) = 1.15 × 10⁻³ m = 1.15 mm