Practice question
Question
A copper wire of length 2.0m and cross-sectional area 2.5×10−6m2 is stretched by a force of 250N. If the Young's modulus of copper is 1.1×1011N/m2, what is the elongation?
Explanation
Young's modulus: Y = FLAΔL. Rearrange: ΔL = FLAY. Substitute: ΔL = 250×2.02.5×10−6×1.1×1011 = 5002.75×105≈1.82×10−3m = 1.82mm. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 1.82mm. This satisfies dimensional consistency and physical conditions given, so option D is scientifically correct.