A copper wire of length 2.50 m and diameter 0.80 mm hangs from a clamp…

Step 1. The stress. $F = Mg$ $= 3.0\ \text{kg} \times 9.8\ \text{m/s}^2 = 29.4$ N. $A = \dfrac{\pi (0.80 \times 10^{-3}\ \text{m})^2}{4}$ $= 5.03 \times 10^{-7}\ \text{m}^2$. The stress is $\dfrac{F}{A} = \dfrac{29.4\ \text{N}}{5.03 \times 10^{-7}\ \text{m}^2}$ $= 58.5\ \text{MPa}$.

Step 2. The strain. $\dfrac{\Delta L}{L} = \dfrac{1.33 \times 10^{-3}\ \text{m}}{2.50\ \text{m}}$ $= 5.32 \times 10^{-4}$.

Step 3. The modulus. $Y = \dfrac{58.5 \times 10^6\ \text{N/m}^2}{5.32 \times 10^{-4}}$ $= 1.10 \times 10^{11}\ \text{N/m}^2$.