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Let a wire be suspended from the ceiling (rigid support) and stretched by a weight W attached at its free end. The longitudinal stress at any point of cross-sectional area A of the wire is

Asked in NEET 2023 · Stress and strain

Answer: (1) W/A

Step-by-step solution

Given: a wire hanging from a rigid support with a weight W at its lower end, cross-sectional area A.

Idea: take an imaginary horizontal cut anywhere in the wire and ask what force the material across that cut must carry.

Everything below the cut is in equilibrium under its weight W (the wire itself is taken as light) and the tension T from above.

T=W at every cut, so the tension is the same all along the wire.

Longitudinal stress is the normal force per unit area of that cut: σ=T/A.

σ=W/A

Why the other options are wrong

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