The elongation of copper wire of cross-sectional area $3.5 \mathrm{~mm}^2$, in the figure shown, is

$$ \left(Y_{\text {Copper }}=10 \times 10^{10} \mathrm{Nm}^{-2} \text { and } g=10 \mathrm{~ms}^{-2}\right) $$

When the load applied to a wire is increased from 5 kg wt to 8 kg wt . The elongation of the wire increases from 1 mm to 1.8 mm . The work done during the elongation of the wire is (acceleration due to gravity $=10 \mathrm{~ms}^{-2}$ )