Question
A closed water tank has a cross-sectional area $A$. It has a small hole at a depth of $h$ from the free surface of water. The radius of the hole is $r$, so that $r \ll \sqrt{\frac{A}{\pi}}$. If $P_0$ is the pressure inside the tank above the water level, and $P_{a}$ is the atmospheric pressure, the rate of flow of the water coming out of the hole is: