Question

On applying a stress of 20 × 10⁸ (N/m²) the length of a perfect elastic wire is doubled. What will be its Young's modulus ? 

(A) 40 × 10⁸ (N / m²) 

(B) 20 × 10⁸ (N / m²) 

(C) 10 × 10⁸ (N / m²) 

(D) 5 × 10⁸ (N / m²)

Answer 1

Correct option: (B) 20 × 10⁸ (N / m²)

Explanation:

stress = 20 × 10⁸ (N / m²)

given : length is doubled

As strain = (Δℓ / ℓ) = {(2ℓ – L) / L} = 1

∴ Y = [(stress) / (strain)] = {(20 × 10⁸) / 1} = 20 × 10⁸ N/m²