I saw this video on YT shorts where the guy demonstrates how it is impossible to suck water beyond 34 feet from the level it is stored at.
[This is the YT short](https://youtube.com/shorts/rWij9gJWcTg?si=5nTRvPUVFUKSaJmH)
On Google it says that the atmospheric pressure equals the pressure exerted by water column.
I don’t understand how that matters! Because in the end the guy attached a vacuum pump to pull the water up.
Also, if the water boils then it should also make steam.
Does PV=nRT apply there? I know it’s not ideal gas but for all practical purposes we use this equation.
In: Physics
To understand that you first need to understand what “sucking” actually is.
It all comes down to pressure. Pressure is atoms and molecules pushing against something, so there can only be positive pressure. By having pressure from the atmosphere and less pressure somewhere else the atmosphere will push the matter towards that point. So if we reduce pressure we are sucking matter towards that point. So when one end of the straw has normal pressure and the other end has no/low pressure the water gets pushed up towards the no/low pressure by the atmosphere.
Now the maximum pressure differential we can achieve in a straw is atmosphere vs nothing, so 1atm or 1,013 hPa. That is enough energy to push up the water 34 feet. After that you only have vacuum above the water, but it can’t go higher because the water is too heavy for the atmosphere to push it higher up. We could go higher by applying more force on the source at the bottom.
Now why does the water boil? Because the boiling point of matter is determined by outside pressure. The less pressure the lower the boiling point becomes. With your mouth or a regular pump you can’t create an actual vacuum with no matter in it(nobody can, it’s just different degrees of how good of a it vacuum is), but with the pump the pressure gets low enough to put the boiling point of water below ambient temperature making it boil at the surface where it touches the vacuum.
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