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Impossable with a pump to suck water from a lake

  1. May 22, 2009 #1
    Hiya
    my question is

    Why is it impossable with a pump to suck water from a lake if you place the pump 15 meters above the water


    I think it has somthing to do with gravity but if anyone could explain it in detail that would be great

    Thanks :)
     
  2. jcsd
  3. May 22, 2009 #2

    madmike159

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    Gold Member

    Re: Pumps

    Well yes the water is held down by gravity.
     
  4. May 22, 2009 #3
    Re: Pumps

    yes but i was thinking what stops me from making a pump so large the i can pump anyways
     
  5. May 22, 2009 #4
    Re: Pumps

    Pumps don't suck. They can only remove the air/water that is already in the line. Then the ambient air pressure pushes the water up. 14.7 psi = 33 feet of water= 10m of water.
     
  6. May 22, 2009 #5
    Re: Pumps

    Have you ever looked at a mercury barometer where the column of mercury is about 760 mm (millimeters) high, with vacuum above the column, and air pressure pushing from the bottom? There is no way that the suction (vacuum) can be made any better. Because the mercury density is 13.6 times higher than water, the absolute max column of water an ideal pump can suck is 760 mm x 13.6 = 10.34 meters (at sea level).
     
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