Answer is: 5

\(\frac{\mathrm{F}_{1}}{\mathrm{~A}_{1}}=\frac{\mathrm{F}_{2}}{\mathrm{~A}_{2}}, \frac{100}{6}=\frac{\mathrm{F}}{1500}, \mathrm{~F}=\frac{50}{3} \times 1500\)
\(\mathrm{F}=50 \times 500=25 \times 10^{3} \mathrm{~N}\)
\(\omega=\overrightarrow{\mathrm{F}} \cdot \overrightarrow{\mathrm{S}}=25 \times 10^{3} \times \frac{20}{100}\)
\(=5 \times 10^{3}=5 \mathrm{~kJ}\)