c
$\mathrm{P}_{1}+\frac{1}{2} \rho \mathrm{v}_{1}^{2}=\mathrm{P}_{2}+\frac{1}{2} \rho \mathrm{v}_{2}^{2}$
$\Delta \mathrm{P}=\frac{1}{2} \rho\left(\mathrm{v}_{2}^{2}-\mathrm{v}_{1}^{2}\right)$
$\Delta \mathrm{P}=\frac{1}{2} \rho\left[(2 \mathrm{v})^{2}-\mathrm{v}^{2}\right]$
$\Delta \mathrm{P}=\frac{3}{2} \rho \mathrm{v}^{2}$