JEE Main 2025 Physics question
A steel wire of length 2 m and Young's modulus 2.0 × 10¹¹ Nm⁻² is stretched by a force. If Poisson ratio and transverse strain for the wire are 0.2 and 10⁻³ respectively, then the elastic potential energy density of the wire is × 10⁵ (in SI units).
Answer: 25
Solution
Longitudinal strain = 10⁻³/0.2 = 5×10⁻³. U = (1/2)×Y×(strain)² = (1/2)×2×10¹¹×25×10⁻⁶ = 25×10⁵ J/m³.