A uniform steel wire 4 m long with a cross-sectional area of 3 × 10⁻⁶ m² is stretched by 1 mm. If Young’s modulus of steel is 2 × 10¹¹ N m⁻², how much energy is stored in the wire?
Correct answer B. 0.075 J
Explanation
The force is F = YAe/L = 2 × 10¹¹ × 3 × 10⁻⁶ × 10⁻³ / 4 = 150 N, so the energy stored is ½Fe = ½ × 150 × 10⁻³ = 0.075 J.
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