\(\gamma=7 / 5\)

\(T _{ i }= T =273+2 0 =293 K\)

\(V_{i}=V\)

\(V _{ f }= V / 10\)

Adiabatic \(TV ^{\gamma-1}=\) constant

\(T _{1} V _{1}^{\gamma-1}= T _{2} V _{2}^{\gamma-1}\)

\(T \cdot V ^{7 / 5-1}= T _{2}\left(\frac{ V }{10}\right)^{7 / 5-1}\)

\(\Rightarrow T _{2}= T .10^{2 / 5}\)

\(\Delta U =\frac{ nfR \left( T _{2}- T _{1}\right)}{2}=\frac{5 \times 5 \times \frac{25}{3} \times\left( T \cdot 10^{2 / 5}- T \right)}{2}\)

\(=\frac{25 \times 25 \times}{6} T \left(10^{2 / 5}-1\right)\)

\(=\frac{625 \times 293 \times\left(10^{2 / 5}-1\right)}{6}\)

\(=4.033 \times 10^{3} \approx 4 kJ\)