$p_{1}+\frac{1}{2} \rho v_{1}^{2}=p_{2}+\frac{1}{2} \rho v_{2}^{2}$

Here, $\quad p_{1}=p_{ atm }+\frac{F}{A}$

and $\quad p_{2}=p_{\text {atm }}$ (as area is too small)

$\therefore \quad p_{ atm }+\frac{F}{A}=p_{ atm }+\frac{1}{2} \rho v_{2}^{2} \quad\left(\because v_{1}=0\right)$

$\Rightarrow \quad v_{2}^{2}=\frac{2 F}{\rho A}$ ...........$(i)$

Range of efflux, $R=v \sqrt{\frac{2 h}{g}}$

$\Rightarrow \quad v^{2}=\frac{R^{2} g}{2 h}$ ...........$(ii)$

From Eqs. $(i)$ and $(ii)$, we get

$\frac{2 F}{\rho A}=\frac{R^{2} g}{2 h}$

$\therefore \quad F =\frac{R^{2} g \times \rho A}{4 h}$

$=\frac{(2)^{2} \times 10 \times 1000 \times 10 \times 10^{4}}{4 \times 1} =10 \,N$