A material has Poisson ratio 0.5. If a rod of material has a longitudinal strain 2 × 10-3, the percentage change in volume is :

Here Poisson's ratio = ∆rr∆llIn this case ∆ll = 2×10-3 and σ = 0.5    ∆rr = σ∆ll           = 2×10-3×5.0 = 10-3Let V be the initial volume and (V + ∆V) be the final volume, then          V = πr2l          V + ∆V = π(r-∆r)2(l+∆l)          ∆V = πr2∆l-2πr l ∆r(Subtracting and simplifying)∆VV = ∆ll-2∆rr         = 2 ×10-3-2×10-3 = 0Correct choice is (4).