Practice question
Question
A steel wire and a copper wire have the same length and cross-sectional area. Both are stretched by the same force. If Young's modulus of steel is 2 × 1011 N/m2 and that of copper is 1.1 × 1011 N/m2, what is the ratio of elongation of the steel wire to the copper wire?
Explanation
Elongation: ΔL = (F L) / (A Y). Ratio: (ΔLsteel)/(ΔLcopper) = Ycopper / Ysteel = (1.1 × 1011) / (2 × 1011) = 11/20 = 0.55. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 0.55. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.