The basic formula for velocity of water flowing out of the small hole in the wall or in the bottom of the container can be derived from Bernoulliu2019s equation and is called Torricelliu2019s law:[math]v=sqrt{2gh} tag*{}[/math]But to get actual velocity magnitude you must also include velocity loss coefficient u03c6:[math]v=varphi cdot sqrt{2gh} tag*{}[/math]