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⚛️ Physics  ·  Mechanical Properties of Solids  ·  NEET & JEE

A wire of length 2 m and cross-sectional area 1 mm² is stretched by 1 mm under a load of 100 N. What is its Youngs modulus?

Answer: 2 × 10¹¹ Pa.

  • A 1 × 10¹¹ Pa
  • B 2 × 10¹¹ Pa
  • C 5 × 10¹⁰ Pa
  • D 1 × 10¹⁰ Pa

Correct answer: B. 2 × 10¹¹ Pa

Explanation: Y = (F/A)/(ΔL/L) = (100/1×10⁻⁶)/(0.001/2) = (1×10⁸)/(5×10⁻⁴) = 2×10¹¹ Pa.

Stress-Strain Curve for a Ductile Metal WireStrainStresselastic limityield pointUTS (max stress)fractureSlope of the straight (elastic) portion = Young's modulus Y; the curve beyond elastic limit shows permanent (plastic) deformation

A typical stress-strain curve: the initial straight line (Hooke's Law region, slope = Young's modulus) ends at the elastic limit; beyond the yield point, deformation becomes permanent, peaking at the ultimate tensile strength before the wire finally fractures.

Concept context

Stress, strain, Hookes law, and the elastic moduli that describe how solids deform and recover under load.

Read the full Mechanical Properties of Solids notes →