A copper rod of radius 0.02m and length 1.0m is subjected to a tensile force producing a stress of 2×107N/m2. What is th
Stress: Stress = FA. Area: A = πr2 = 3.14×(0.02)2 = 3.14×4×10−4 = 1.256×10−3m2. Force: F = Stress×A = 2×107×1.256×10−3 = 2.512×104N. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 2.512×104N. This satisfies dimensional consistency and physical conditions given, so option A is scientifically correct.
Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.