Practice question
Question
A steel wire of length 2.8m and cross-sectional area 4×10−6m2 is stretched by a force producing a strain of 1.5×10−4. If the Young's modulus of steel is 2×1011N/m2, what is the elongation?
Explanation
Strain: Strain = ΔLL. Rearrange: ΔL = Strain×L = 1.5×10−4×2.8 = 4.2×10−4m = 0.42mm. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 0.42mm. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.