Torricelli’s law states that the velocity ($v$) of a fluid exiting an orifice is equal to the velocity that a body would attain if it were dropped from a height equal to the depth of the fluid ($h$) above the orifice, Torricelli’s law equates the kinetic energy of the fluid flowing out of the opening to  potential energy of the fluid due to its height above the opening. Mathematically, Torricelli’s law is expressed as,

Where:

• $v$ is the velocity of the fluid as it exits the orifice,
• $g$ is the acceleration due to gravity,
• $h$ is the height of the fluid above the orifice.