# This dam is like a water cannon. Let’s do some physics!

When people build Dams-huge walls blocking entire lakes and rivers-they must build an overflow channel called a spillway to alleviate flooding.

Spillways can be as simple as the path of water flowing over the top of the dam, or more complicated, like side channels. Sometimes, there is only a large hole at the bottom of the dam (the dry side) so that water can shoot out like a huge water cannon.This is how it works Fournier Hydropower Station in Brazil. There is one Nice video Shows the water flowing out-it looks like a river in the air because it basically Yes The river in the air.

But the really cool physical principle of this spillway is that the speed of the water coming out of the hole mainly depends on the depth of the water behind the dam. Once the water leaves the tube, it is essentially like a ball thrown at the same speed. Yes, you know what I am going to do: I will use the trajectory of the water leaving the spillway to estimate the depth of the water in the reservoir.

The relationship between water flow and depth actually has a name-called Torricelli’s LawImagine you have a bucket of water and you poke a hole on the side near the bottom. We can use physics to calculate the speed at which water flows out.

Let us first consider the change in the water level as the water is discharged in a short time interval. This is a chart:

Looking at the top of the bucket, the water level will drop—even if it’s just a little bit. It doesn’t matter how much the water level drops; what we are interested in is the quality of the water, which I will label as dMeterIn physics, we use “d” to mean different amounts of things, so this may be just a small amount of water.The drop in the top water level means that the water must go somewhereIn this case, it leaves through the hole. The quality of the water flowing out must also be dMeter. (You must keep track of all the water.)

Let us now consider this issue from an energy perspective. Water is a closed system, so the total energy must be constant. In this case, there are two energies to consider. First, there is gravitational potential energy (youG = Magnesium). This is the energy related to the height of the object above the surface of the earth, and it depends on the height, mass, and gravitational field (G = 9.8 N/kg). The second type of energy is kinetic energy (K = (1/2)mv2). This is an energy that depends on mass and speed (v) Object.