Practice question
Question
A copper wire of length 1.6m and cross-sectional area 1.8×10−6m2 is stretched by a force of 180N. 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 = 180×1.61.8×10−6×1.1×1011 = 2881.98×105≈1.45×10−3m = 1.45mm. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 1.45mm. This satisfies dimensional consistency and physical conditions given, so option A is scientifically correct.