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  • Category: Miscellaneous

    10 meters is the maximum you can suck on Earth

    Earlier this week I asked a question. Here is it. Does vacuum suck water and denser liquids? . I knew the answer to that question. I wanted to clarify because my seniors in job were not agreeing with me.
    Vacuum occurs when you rapidly vacate a medium such as air from something. We all know that there is air enclosed in everything. A glass is only half filled and the other half is air. So the glass achieves vacuum when you vacate that air. But this vacuum, if high enough, can even cause water to boil under room temperature. I am working in a company that provides engineering solutions and vacuum is often our best solution. I long feared this vacuum. I hated it because I never understood it fully. But "there is something in nothing", makes me very curious. If you want to know more about vacuum read from that link.

    Now I saw an impressive video that proposed a "space straw". One side of a straw would be in space/under vaccuum and the other side dipped inside an ocean. A straw works like this- when you dip a small diameter tube such a straw into a liquid, the liquid due to its density will rise. It is called capillary action. But the liquid stops at a level on the straw. As the saying goes, it's only half full with other half occupied by air. You suck the air out and the liquid displaces in the place of air, following the path, falls in your mouth. What could suck air better than vaccum after all? And what has more vacuum than space after all? So all the air is displaced through such space straw into vacuum now and the liquid can now rise. But there is an issue. The water never rises above 10 meters. Here's why.
    Pressure difference=density*height*acceleration due to gravity
    Let's assume its a perfect vaccum, which space almost is, so 0 N/m2 is the pressure on one side and atmospheric pressure 101325 N/m2 on another. Ideally, all of the air is sucked out.
    0-101325= 1000*(-9.8) * height of liquid column sucked. Approximating the value of acceleration due to gravity as 10 m/s2, we obtain height of liquid as 10 meters. Even if you sucked all the air out of earth, you cannot suck a liquid that is more than 10 meters deep. I took so much pain to calculate and understand all this haha.
  • #682491
    Sorry. The suction lift limitation only happens in case of surface pumps and not applicable to jet and submersible pumps. Those pumps work under pressure higher than the atmospheric pressure, and as a consequence can provide more suction lift. But under atmospheric conditions it is impossible to attain more than 10 meters of suction lift for the above reason.
    The stronger a light shines the darker are the shadows around it.

  • #682512
    True. Your statement is correct when the pumps are working at atmospheric pressure. But if you increase or decrease the pressure the sucking capacity may increase or decrease. That is why we are able to get water from deep inside the earth by using jet or submersible pumps.
    always confident

  • #682522
    This is a good example of basic Physics of pressures across a liquid column and depending upon the atmospheric pressure the height of liquid column will be there. On a planet where the planet's atmospheric pressure is lower than the Earth, the height of column will be decreased accordingly. The fundamentals of physical processes are best understood with the application of basic principles of Physics. We have read them in our high school classes but they become clearer to us only when we try to understand them in their totality seeing some real life examples.
    Knowledge is power.

  • #682529
    The author made some good revelation on the subject of pressure and liquids and this content is very much suited to be a resource content so that many students would benefit.
    K Mohan @ Moga
    'Idhuvum Kadandhu Pogum "
    Even this challenging situation would ease

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