Loss in \(K \cdot E=\frac{1}{2} \frac{M_{1} M_{2}}{M_{1}+M_{2}} V^{2}\left(1-e^{2}\right)\)

\(=\frac{1}{2} \times \frac{5 \times 10^{3} \times 15 \times 10^{3}}{20 \times 10^{3}} \times(2)^{2} \times\left(1-0^{2}\right)\)

\(=\frac{1}{2} \times \frac{75 \times 10^{3}}{20} \times 4\)

\(=7.5 kJ\)