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A steel wire having a radius of 2.0 mm, carrying a load of 4 kg, is hanging from a ceiling. Given that g = 3.1 π m s⁻², what will be the tensile stress that would be developed in the wire ?

1. 5.2 × 10⁶ N m⁻²
2. 6.2 × 10⁶ N m⁻²
3. 4.8 × 10⁶ N m⁻²
4. 3.1 × 10⁶ N m⁻²

Correct answer: 3.1 × 10⁶ N m⁻²

Solution

F = mg = 4 * 3.1*pi N. Area = pi r^2 = pi*(2e-3)^2. Stress = F/A = (4*3.1*pi)/(pi*4e-6) = 3.1e6 N/m^2.

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