Practice question
Question
A steel wire of length 2.6m and cross-sectional area 2×10−6m2 is stretched by a force of 400N. If the Young's modulus of steel is 2×1011N/m2, what is the elongation?
Explanation
Young's modulus: Y = FLAΔL. Rearrange: ΔL = FLAY. Substitute: ΔL = 400×2.62×10−6×2×1011 = 10404×105 = 2.6×10−3m = 2.6mm. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 2.6mm. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.