Practice question
Question
A steel wire of length 2.5m and cross-sectional area 3.5×10−6m2 is stretched by a force of 350N. If the elongation is 0.2mm, what is the Young's modulus of steel?
Explanation
Young's modulus: Y = FLAΔL. Substitute: ΔL = 0.2×10−3m. Y = 350×2.53.5×10−6×0.2×10−3 = 8757×10−10≈1.25×1012N/m2. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 1.25×1012N/m2. This satisfies dimensional consistency and physical conditions given, so option D is scientifically correct.