Does Fluid medium travel from High P to low P? Or Low P to High P?

[ipodtouch]

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I assumed that Water in a pipe travels from Low Pressure to High Pressure.

But this problem in BR says exactly opposite.

"Water travels down a pipe because hydrostatic pressure is greater at the output end of the tube than the input end."

So.... water travels towards higher P?

 

[chiddler]

that can't be right

😕

 

[milski]

High to low. The low pressure at the open lower end of the pipe is the atmospheric pressure, where the fluid ultimately ends.

The quote does not make much sense but can be made correct if you remove "because" and replace it with a full stop.

 

[SaCkO]

Then why does water flow out of the faucet at the bottom of tank.. isnt the opening of faucet under the pressure of atomosphere. and since the tank is closed the pressure inside the tank is equal to gauge pressure which is lower than atmosphere..
can somebody please explain?

 

[chiddler]

Then why does water flow out of the faucet at the bottom of tank.. isnt the opening of faucet under the pressure of atomosphere. and since the tank is closed the pressure inside the tank is equal to gauge pressure which is lower than atmosphere..
can somebody please explain?

Gauge pressure is total pressure minus atmospheric.

Try to figure out the answer with this information.

 

[Dasypus]

SaCkO, if the tank is really tightly sealed, and no glug-glug of air back into the tank is permitted (which would mean that the pressure could not equalize), then I believe you're right that it would not flow.

The more usual situation is that the tank has a vent somewhere, so that air can flow in as water flows out. That makes it so that the pressure at the faucet, just inside the tank, is equal to atmospheric pressure plus gauge pressure, while the pressure at the faucet just outside the tank is only atmospheric pressure, thus driving the water out.

 

[chiddler]

SaCkO, if the tank is really tightly sealed, and no glug-glug of air back into the tank is permitted (which would mean that the pressure could not equalize), then I believe you're right that it would not flow.

The more usual situation is that the tank has a vent somewhere, so that air can flow in as water flows out. That makes it so that the pressure at the faucet, just inside the tank, is equal to atmospheric pressure plus gauge pressure, while the pressure at the faucet just outside the tank is only atmospheric pressure, thus driving the water out.

Fluid stops leaving the container only when pressures are equal. So it is completely possible for a container to have water deep enough to exceed atmospheric pressure even if it is completely sealed off from the atmosphere.

 

[ipodtouch]

The problem involved a Toilet. It was:

What is true of a functioning siphon during operation?
Answer:Water flows because hydrostatic pressure is greater at the output end of the tube than the input end.


The explanation was:

"A siphon works because the two ends of the siphon tube are at different heights, and thus different potential energies. In order to have water flow from the intake end to the output end, there must be a net pressure difference where the gauge pressure is greater at the output end. This occurs when the output end is at a lower height, thus it is at a point of greater hydrostatic pressure."

 

[SaCkO]

Fluid stops leaving the container only when pressures are equal. So it is completely possible for a container to have water deep enough to exceed atmospheric pressure even if it is completely sealed off from the atmosphere.

Thats doesn't work in regular water tanks, lets say the depth is 10 min then pressure due to water is : 10*1000*10= 1*10^5 pa
if this tank is sealed from top and water is filled to the top then even you open the faucet water should not go out because 1 atm = 101000 > 100000

 

[chiddler]

Thats doesn't work in regular water tanks, lets say the depth is 10 min then pressure due to water is : 10*1000*10= 1*10^5 pa
if this tank is sealed from top and water is filled to the top then even you open the faucet water should not go out because 1 atm = 101000 > 100000

that is 10 meters. now make it 20 meters.

101000 < 200000

it is completely possible for water to leave from an airtight canister if hydrostatic pressure is high enough.

 

[SaCkO]

that is 10 meters. now make it 20 meters.

101000 < 200000

it is completely possible for water to leave from an airtight canister if hydrostatic pressure is high enough.

I know but i was just giving an example where it doesnt
So from what i understood the water tanks are usually opened from the top so that atmospheric pressure can push the water down

 

[chiddler]

all i wrote was that it was possible =/

"So it is completely possible for a container to have water deep enough to exceed atmospheric pressure"

 

[Dasypus]

I know but i was just giving an example where it doesnt
So from what i understood the water tanks are usually opened from the top so that atmospheric pressure can push the water down

Also so the pressure from the water draining out doesn't crush the tower inward like a water bottle sucked on too hard.

 

[Morsetlis]

Change "because" to "causing".