Practice question
Question
An aluminium wire of length 1.8m and cross-sectional area 2×10−6m2 is stretched by a force producing a strain of 2×10−4. If the Young's modulus of aluminium is 7×1010N/m2, what is the force applied?
Explanation
Young's modulus: Y = StressStrain. Stress: Stress = Y×Strain = 7×1010×2×10−4 = 1.4×107N/m2. Force: F = Stress×A = 1.4×107×2×10−6 = 28N. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 28N. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.