Correct option: (A) 15 × 10–4 m
Explanation:
W = weight of the cord = mg
as density = [{mass} / {volume}] i.e. d = m/v
∴ W = g ∙ d ∙ v
W = g ∙ d ∙ A ∙ L -------- volume = area × length
∴ W = 10 × 1500 × A × 10
W = 15A × 104 N
Stress = W/A
= {(15A × 104) / A}
Stress = 15 × 104 N/m2
As the weight of rubber acts at centre of gravity only upper half of length is stretched.
i.e. L' = (10 / 2) = 5 cm
∴ strain = (ℓ / L') = (ℓ/5) = [(stress) / Y]
∴ (ℓ/5) = [{15 × 104} / {5 × 108}] = 15 × 10–4 m