The maximum elongation of a steel wire of 1 m length if the elastic limit of steel and its Young's modulus, respectively, are 8×10^8 N m^-2 and 2×10^11 N m^-2, is :

1. 8 mm

2. 4 mm

3. 0.4 mm

4. 40 mm

Doubtly Asked 30 Oct 2026 NEET UG 2024 Practice test neet Save WhatsApp Report

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Answer: 2. 4 mm

Key idea: The largest stress the wire can bear without permanent change is the elastic limit. Use \(Y=\frac{\text{stress}}{\text{strain}}\).

Strain \(=\frac{8\times10^{8}}{2\times10^{11}}=4\times10^{-3}\).

Elongation \(=\text{strain}\times L=4\times10^{-3}\times1=4\times10^{-3}\) m \(=4\) mm.

Option 2.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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