Things you always wanted to know the answer to [Vol. 3]
Discussion
talksthetorque said:
Air pressure reduces with altitude. Climbers needing oxygen, people getting sucked out of holes in planes etc etc.
So if air pressure was responsible for water pressure, building a big water tower would reduce the water pressure.
People don't get sucked out of holes in planes; they get pushed out by the rush of escaping higher pressure air from inside. So if air pressure was responsible for water pressure, building a big water tower would reduce the water pressure.
Ayahuasca said:
People don't get sucked out of holes in planes; they get pushed out by the rush of escaping higher pressure air from inside.
That's not strictly true. Even at parity between in hull pressure and ambient pressure, there is a suction effect from the speed of the airflow over the a/c.MartG said:
Your original post specified 'atmospheric pressure' as one option, not 'pumped or not' 
Gravity feed would work in a vacuum ( assuming the liquid didn't boil off )
No it wouldn't. Lets take the water tower as an example, if the top of it was sealed 100% airtight the water wouldn't flow out. Take a wet beer mat, place it over a full pint glass and turn it over, the liquid stays in. So why isn't it falling out due to gravity?Gravity feed would work in a vacuum ( assuming the liquid didn't boil off )
Ayahuasca said:
talksthetorque said:
Air pressure reduces with altitude. Climbers needing oxygen, people getting sucked out of holes in planes etc etc.
So if air pressure was responsible for water pressure, building a big water tower would reduce the water pressure.
People don't get sucked out of holes in planes; they get pushed out by the rush of escaping higher pressure air from inside. So if air pressure was responsible for water pressure, building a big water tower would reduce the water pressure.
What small sucking force there is, it's basically the same as buoyancy - differential pressure one side of a body to another producing a key force.
RATATTAK said:
glenrobbo said:
Cold said:
JagerT said:
grumbledoak said:
What would it take to stop PHers using 'Quote All'?
Not sure,what do other people think ?227bhp said:
MartG said:
Your original post specified 'atmospheric pressure' as one option, not 'pumped or not'
Gravity feed would work in a vacuum ( assuming the liquid didn't boil off )
No it wouldn't. Lets take the water tower as an example, if the top of it was sealed 100% airtight the water wouldn't flow out. Take a wet beer mat, place it over a full pint glass and turn it over, the liquid stays in. So why isn't it falling out due to gravity?Gravity feed would work in a vacuum ( assuming the liquid didn't boil off )
Halmyre said:
227bhp said:
MartG said:
Your original post specified 'atmospheric pressure' as one option, not 'pumped or not'
Gravity feed would work in a vacuum ( assuming the liquid didn't boil off )
No it wouldn't. Lets take the water tower as an example, if the top of it was sealed 100% airtight the water wouldn't flow out. Take a wet beer mat, place it over a full pint glass and turn it over, the liquid stays in. So why isn't it falling out due to gravity?Gravity feed would work in a vacuum ( assuming the liquid didn't boil off )
Edited by 227bhp on Saturday 25th November 23:48
227bhp said:
MartG said:
Your original post specified 'atmospheric pressure' as one option, not 'pumped or not'
Gravity feed would work in a vacuum ( assuming the liquid didn't boil off )
No it wouldn't. Lets take the water tower as an example, if the top of it was sealed 100% airtight the water wouldn't flow out. Gravity feed would work in a vacuum ( assuming the liquid didn't boil off )
Anyway, you are altering the conditions by specifying a sealed water tower - they aren't sealed. Air pressure acts on both the water in the water tower and on your tap - but the difference in air pressure is negligible compared to the pressure water is supplied at. Standards require a minimum supply pressure to domestic premises equivalent to 7m static head, or about 1.7 atmospheres.
Wiccan of Darkness said:
RATATTAK said:
glenrobbo said:
Cold said:
JagerT said:
grumbledoak said:
What would it take to stop PHers using 'Quote All'?
Not sure,what do other people think ?kowalski655 said:
Wiccan of Darkness said:
RATATTAK said:
glenrobbo said:
Cold said:
JagerT said:
grumbledoak said:
What would it take to stop PHers using 'Quote All'?
Not sure,what do other people think ?227bhp said:
No it wouldn't. Lets take the water tower as an example, if the top of it was sealed 100% airtight the water wouldn't flow out.
It would if the tower's more than 10.3 meters high. Below that atmospheric pressure at the other end will keep the water in, but that's against a vacuum. If the top is vented the atmospheric pressure difference will be less than you'd get by waving your hands over it. RizzoTheRat said:
It would if the tower's more than 10.3 meters high. Below that atmospheric pressure at the other end will keep the water in, but that's against a vacuum. If the top is vented the atmospheric pressure difference will be less than you'd get by waving your hands over it.
Exactly this. See "Torricelli vacuum" but with water instead of mercury mickk said:
kowalski655 said:
Wiccan of Darkness said:
RATATTAK said:
glenrobbo said:
Cold said:
JagerT said:
grumbledoak said:
What would it take to stop PHers using 'Quote All'?
Not sure,what do other people think ?Gassing Station | The Lounge | Top of Page | What's New | My Stuff