($P_0$ = atmospheric pressure)
$\mathrm{P}_{0}+\rho \mathrm{gh}_{3}=\mathrm{P}_{0}+1 / 2 \rho \mathrm{v}^{2}$
$1 / 2 \rho v^{2}=\rho g h_{3}$
$\mathrm{P}_{0}=\mathrm{P}_{2}+1 / 2 \rho \mathrm{v}^{2}$
$\mathrm{P}_{2}=\mathrm{P}_{0}-\rho \mathrm{gh}_{3}$


($P_0$ = atmospheric pressure)
