Calling all Mechanical Engineers!

Mark · Aug 9, 2008

This exposes my ignorance, but always being willing and ready to learn, I have what may seem a simple question.

How does an inverted chicken waterer keep from overflowing? It seems to me that the water in the container, being much higher above the holes in the bottom, would form a head pressure and force the water out.....until it reached a level condition.

So, please explain to me, the physics involved. Thanks.

old · Aug 9, 2008

Sort of simple. Water in the out side comes up to a point it stops air from being able to go in. No air in no water out. Works sort of like you putting your finger over the end of a drinking straw and then pulling it out of the glass. The water stays in because no air can come in. And yes theres a more technical way to explain it but I'll not post it LOL
Hobby farm

Dan-IA · Aug 9, 2008

It does not overflow because of water cohesion and tension. The water is held inside the container because there is a limit to how much whatever air in the container can expand. The water, which has a finite and static volume, sticks together. The other part to consider is the force of the water in the trough that pushes back against the supply in the tank. Since water cannot be compressed and the hole in the waterer sits below the surface of the water, only a certain amount will be in the waterer and available for consumption.

By placing the waterer on a sufficiently uneven floor and pointing the hole to the high point, you can make it overflow. You can also cause overflow by poking a hole in the container, which allows air to leak in.

teddy52food · Aug 9, 2008

Actually, It is the air pressure holding it up.

Jerry/MT · Aug 9, 2008

Atmospheric pressure( 14.7 psia +/-) will hold up a column of water ~33ft+/- high. Just do a free body diagram of the forces on the water and you"ll be able to understand it.
The pressure on the bottom of the waterer is just the density (or specific weight) times the height; 62.4 lb/cu ft X the height of the container. That has to be greater equal atmospheric pressure to cause the water to flow out. So,

62.4 x H = (14.7 x 144)

H = 2116.8/62.4 = 33.9 ft.
So 14.7 psia will hold up a water column of 33.9 ft. anyhigher and the water runss out until the column is 33.9 ft again.

farmer101IL · Aug 9, 2008

(quoted from post at 10:49:15 08/09/08) Atmospheric pressure( 14.7 psia +/-) will hold up a column of water ~33ft+/- high. Just do a free body diagram of the forces on the water and you"ll be able to understand it.
The pressure on the bottom of the waterer is just the density (or specific weight) times the height; 62.4 lb/cu ft X the height of the container. That has to be greater equal atmospheric pressure to cause the water to flow out. So,

62.4 x H = (14.7 x 144)

H = 2116.8/62.4 = 33.9 ft.
So 14.7 psia will hold up a water column of 33.9 ft. anyhigher and the water runss out until the column is 33.9 ft again.

uh huh riiiiggghhhhhhtttttt gotcha , right up to free body

twopop · Aug 9, 2008

besides all the science here. it is that vacuum holds the water in. when the level of water on the outside goes down to let air in the rim fills up again until the vacuum level is reached

MarkB_MI · Aug 9, 2008

If you've ever seen a mercury barometer, the principle is exactly the same. The air pressue inside the container is essentially zero (absolute). the atmospheric air pressure is 14.7 psi absolute. So you have a pressure differential that is trying to push the water into the tank. When your chicken drinks out of the tank a little air slips into the tank, raising the air pressure in the tank; water runs out until the weight of the water once again equals the pressure of the air pushing it up into the tank.

Mark · Aug 9, 2008

Thank you, gentlemen. I do understand it much more clearly now. I take it as a constant displacement of air for water.....and therefore, an equilibrium of sorts is maintained. That may not be exact.....but I do have the gist of the matter, straight. Thanks!

wallacedw · Aug 9, 2008

HA!!!! You guys are ALL WRONG! It's the GREMLIN'S!!!! They did it.. yeah.. yeah.. THAT'S the ticket!!! lol

Sorry, I couldn't help it!

JerryMT · Aug 9, 2008

It's an engineering technique that looks at all the forces acting on an object. You then sum them up and what results is the simple equation in my response.

Anonymous-0 · Aug 9, 2008

au, enought that crap, i gots au tractor ta fix!when i get er done ill post a picture

buickanddeere · Aug 9, 2008

It"s air pressure, not surface tension.
The air inside the container can expand indefinately.

tedbo · Aug 9, 2008

Ouch! Y'all are makin' my head hurt! I think I popped a brain cell or two!
I'm not completely stupid,although some parts are missing!

I can sorta follow along and get the gist of it,just not the finer points.
I am glad we have some great people here that truly do know this stuff. it makes me really try to follow along and actually lkearn something.

Thank You!!!

Calling all Mechanical Engineers!

Mark

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old

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Dan-IA

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teddy52food

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Jerry/MT

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farmer101IL

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twopop

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MarkB_MI

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Mark

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wallacedw

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JerryMT

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Anonymous-0

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buickanddeere

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tedbo

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