A brass rod has length 0.2m area of cross section 1.0cm² and Young's modulus 10¹¹Nm^–2. If it is compressed by 5kg. wt along its length then the change in its energy will be

l = 2 x 10^-1 mA = 1 x 10^-4 m²
y = 10¹¹ Nm^-2, F = 5 x 9.8N
$\mathrm{w}=\frac{1}{2}\frac{{\mathrm{F}}^2\mathrm{l}}{\mathrm{Ay}}=\frac{\mathrm{l}}{2} \mathrm{x} \frac{25 \mathrm{x} 9.8 \mathrm{x} 9.8 \mathrm{x} 2 \mathrm{x} {10}^{-1}}{1 \mathrm{x} {10}^{-4} \mathrm{x} {10}^{11}}$
w = 2.4 x 10^-5 J, As the work is done on the rod the energy of the rod increases.