با توجه به دادههای مسئله داریم:
$\begin{align}
& U=E-K\xrightarrow[K=\frac{1}{2}m{{v}^{2}}]{E={{K}_{\max }}} \\
& U=\frac{1}{2}mv_{m}^{2}-\frac{1}{2}m{{v}^{2}} \\
& \frac{U}{K}=\frac{\frac{1}{2}m(v_{m}^{2}-{{v}^{2}})}{\frac{1}{2}m{{v}^{2}}}\xrightarrow{\frac{U}{K}=\frac{7}{9}}\frac{7}{9}=\frac{v_{m}^{2}-{{v}^{2}}}{{{v}^{2}}} \\
& \frac{7}{9}={{(\frac{{{v}_{m}}}{v})}^{2}}-1\Rightarrow {{(\frac{{{v}_{m}}}{v})}^{2}}=\frac{16}{9}\Rightarrow \frac{{{v}_{m}}}{v}=\frac{4}{3}\Rightarrow \frac{v}{{{v}_{m}}}=\frac{3}{4} \\
\end{align}$