Question

A water tank has a hole 3.0 cm^2 in area located 2.0 m below the water
surface. How many kilograms of water emerge from the hole per second?

Answer 1

The mass of water that flows from a hole for time $\Delta t$

$$\Delta m=\rho Av\Delta t$$

Here

$$v=\sqrt{2gH}$$

Finally,

$$\frac{\Delta m}{\Delta t}=\rho A\sqrt{2gH}\\ =1000*3.0*10^{-4}*\sqrt{2*9.8*2.0}=1.88\:\rm kg/s$$