Question

A metallic rod breaks when strain produced is 0.2%. The Young’s modulus of the material of the rod is 7×10⁹ N m⁻². What should be its area of cross-section to support a load of 10⁴ N?

• A. 7.1×10⁻⁸ m²
• B. 7.1×10⁻⁶ m²
• C. 7.1×10⁻⁴ m²
• D. 7.1×10⁻² m²

Hint:

Breaking condition occurs at maximum permissible strain.

Answer 1

The Correct Option is B

Step 1: Strain, ε = 0.2% = 2×10⁻³
Step 2: Stress, σ = Yε = 7×10⁹ × 2×10⁻³ = 1.4×10⁷
Step 3: Area, A = (F)/(σ) = (10⁴)/(1.4×10⁷) ≈ 7.1×10⁻⁶ m²