Why does the water boil if it sucked beyond 34 feet in height?

475 viewsOtherPhysics

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

7 Answers

Anonymous 0 Comments

When you suck on a straw, you lower the pressure above the liquid, and there’s atmospheric pressure on the other end. So if imagine that in your mouth there is vacuum, and atmospheric pressure at the bottom of the straw, there’s a 1 atm pressure difference pushing the water up. But the water is being pulled down by gravity. So the force on the water is 1atm minus the weight of the water. Once the weight of the water is equivalent to atmospheric pressure, which occurs when the water is 34 ft tall, there is no net force pushing the water up anymore.

It doesn’t actually have to deal with water boiling. Even if water didn’t boil under those conditions (0atm and room temperature) you still couldn’t pull water more than 34 feet up with vacuum.

A (non vacuum) pump applies a positive pressure on the source of the water, while a vacuum pump lowers the pressure at the destination. Vacuum pumps are inherently limited since pressure can never be lower than zero. Traditional pumps are not limited by atmospheric pressure, since they you can always keep raising pressure.

You are viewing 1 out of 7 answers, click here to view all answers.