Stress, Strain & Elasticity — A/L Physics

How do I practise Stress, Strain & Elasticity?

1 question with a worked solution

1. A steel wire of length 2.0 m and uniform cross-sectional area 1.0 × 10⁻⁶ m² is stretched within its elastic limit by a tensile force of 200 N. If the Young's modulus of steel is Y = 2.0 × 10¹¹ N m⁻², what is the extension (ΔL) produced in the wire?
   1. A) 2.0 mm (2.0 × 10⁻³ m)
   2. B) 0.5 mm (0.5 × 10⁻³ m)
   3. C) 4.0 mm (4.0 × 10⁻³ m)
   4. D) 1.0 mm (1.0 × 10⁻³ m)
   Check my answer

   Correct answer: A) 2.0 mm (2.0 × 10⁻³ m)

   From Hooke's Law and the definition of Young's Modulus: Y = (F / A) / (ΔL / L) = F L / (A ΔL). Rearranging for extension: ΔL = F L / (A Y) = (200 N × 2.0 m) / (1.0 × 10⁻⁶ m² × 2.0 × 10¹¹ N m⁻²) = 400 / (2.0 × 10⁵) = 2.0 × 10⁻³ m = 2.0 mm.

   Show worked solution

   Step 1: Formula: ΔL = F·L / (A·Y). Step 2: ΔL = (200 × 2.0) / (1.0 × 10⁻⁶ × 2.0 × 10¹¹) = 400 / (2.0 × 10⁵) = 2.0 × 10⁻³ m = 2.0 mm. Answer: 2.0 mm (2.0 × 10⁻³ m).
   Modelled on: the A/L Physics examination pattern

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Where does Stress, Strain & Elasticity fit in the syllabus?

Unit 10.1 · Year 2 · Term 3