با استفاده از رابطه‌ی $F=\frac{\Delta P}{\Delta t}$ می‌توان نوشت: ${{F}_{1}}=F,{{F}_{2}}=2F\left\{ \begin{matrix} {{v}_{{}^\circ 1}}=0\Rightarrow {{P}_{{}^\circ 1}}=0  \\ {{P}_{1}}=P  \\ \end{matrix} \right.\Rightarrow \Delta {{P}_{1}}=P$ $\Delta P=F\Delta t\xrightarrow{\Delta {{t}_{1}}=\Delta {{t}_{2}}=t}\frac{\Delta {{P}_{2}}}{\Delta {{P}_{1}}}=\frac{{{F}_{2}}}{{{F}_{1}}}\Rightarrow \frac{\Delta {{P}_{2}}}{P}=\frac{2F}{F}\Rightarrow \Delta {{P}_{2}}=2P$ $\Delta {{P}_{2}}={{P}_{2}}-{{P}_{{}^\circ 2}}\Rightarrow 2P={{P}_{2}}-0\Rightarrow {{P}_{2}}=2P$