An aluminium wire (Y = 7.0 × 10¹⁰ Pa) and a rubber cord (Y = 4.0 × 10⁶ Pa) are each under a stress…

Step 1. Aluminium. $\dfrac{(2.0 \times 10^{6}\ \text{Pa})^2}{2 \times 7.0 \times 10^{10}\ \text{Pa}} = 28.6\ \text{J/m}^3$.

Step 2. Rubber. $\dfrac{(2.0 \times 10^{6}\ \text{Pa})^2}{2 \times 4.0 \times 10^{6}\ \text{Pa}} = 5.0 \times 10^{5}\ \text{J/m}^3$.

Step 3. Ratio. $\dfrac{5.0 \times 10^{5}\ \text{J/m}^3}{28.6\ \text{J/m}^3} = 1.75 \times 10^{4}$.