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Physics behind flow of water from a bottle

  1. May 28, 2014 #1
    Hello Guys;

    If u turn a water bottle(full of water) upside down and bring it down towards water present in a bigger vessel than the bottle's mouth. Then water from the bottle will stop flowing at the moment the bottle's opening (mouth) gets immersed in the water present in the vessel why ?
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  3. May 28, 2014 #2
    this would happen at the moment the vacuum created in the wake of the water flow becomes strong enough to support the weight of the water in the bottle. it won't necessarily be at the moment the mouth of the bottle touches the larger fluid surface in the bigger vessel.
  4. May 28, 2014 #3
    Good answer, but...

    To be physically correct, if we take the surface of the larger body of water as a datum level, it would be the atmospheric pressure on the surface of the larger body of water supporting the pressure from the height of water in the bottle above the surface of the water.

    It acts the same way as a barometer.

    With lower atmospheric pressure, more of the water would flow out of the bottle.
    In fact, if the atmospheric pressure could be zero ( a vacuum ), all the water would flow out of the bottle.
  5. May 29, 2014 #4


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    What replaces the water in the bottle, when the water does flow? Is this still possible when the mouth is submerged?
  6. May 29, 2014 #5


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    Couldn't it still "fill up" with vaccum? I would still consider that to be water flow.
  7. May 29, 2014 #6


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    Right, but leads to the pressure imbalance mentioned by others already. I was pointing out what is different between the two cases.
  8. May 29, 2014 #7
    how exactly is the vaccum created inside the bottle isn't it like the air flows inside the bottle at the same time the water flows out of it , this can be seen in water dispensers when u open the tap , water bubbles raise inside the water can?
  9. May 29, 2014 #8
    I think air is the thing that replaces water , but i'am not sure how this will work in vaccum ? If air is the thing that is replacing , then water will not stop to flow at the moment the mouth gets submerged in case of vaccum.
  10. May 29, 2014 #9
    So u are saying that it does not depend on the criteria of submergence???
  11. May 29, 2014 #10
    Under normal situations, in order to empty a bottle of water, you have to fill it with air. If you turn a bottle upside down, water leaks out the opening, and air leaks in. But if you put the top of the bottle underwater, you can't get air to leak in anymore, so the bottle can't empty.

    (but if your bottle is over about 10m tall, you might see the water at the top of the inverted bottle start to boil and a layer of water vapor form at the top)
  12. May 29, 2014 #11

    What in case of vaccum that is the main concept i dont understand?
  13. May 30, 2014 #12
    You need to be more clear.
  14. May 31, 2014 #13
    I need to understand how the water flow will be in case of vaccum , will it terminate at the moment the bottles opening is submerged in the bigger water surface(this is the case where air is present) or not ?
  15. May 31, 2014 #14
    Where is this vacuum present? If it's present throughout your system, then the water flow won't terminate until all the water from the bottle has flown into the bigger container (Because there's no air pressure to counter the weight of the water in the bottle ) If you're talking about vacuum present above the column of water in the bottle, then it would terminate as soon as the weight of the column of water is exactly balanced by the atmospheric pressure on the rest of the water surface (the water in the larger container I mean ). It doesn't depend on when the bottle opening comes in contact with the larger surface (if it doesn't come in contact at all, then all your water would flow out of course )
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