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Elevator straw

  1. Sep 30, 2009 #1
    You have a glass of water on the first floor. You are on the second floor with a very long straw. You put the straw in the water. How can you drink the water or get it to the second floor? (Without using anything except what is stated in the problem) How do you continuously drink it?
     
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  3. Sep 30, 2009 #2

    berkeman

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    Well, other than sucking real hard, there is at least one other answer. Is this for homework or other schoolwork? What is the context of the question?
     
  4. Sep 30, 2009 #3
    my teacher asked me if there was a possible way but I can't think of it. It's just for fun.
     
  5. Sep 30, 2009 #4

    russ_watters

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    Humans are not capable of generating the required pressure for that with their mouths/lungs. Not sure what other methods there may be...
     
  6. Sep 30, 2009 #5
    That's gotta be one fine straw. Offer it to the first passing kid you see if he'll bring you the glass of water. Or you can always walk down stairs and get it yourself.
     
  7. Sep 30, 2009 #6
    I only found one online reference of dubious source that placed suction through a straw, using mouth and tough, rather than lungs (1 psi), at 4 psi. I think it's doable, or nearly so.
     
  8. Sep 30, 2009 #7

    berkeman

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    Well, let's not give it away to the OP, but think about how else you get soda from the glass into your mouth with a straw...

    jimlee -- any ideas?
     
  9. Oct 1, 2009 #8
    No such thing as suction really.............fluid is pushed up the straw by atmospheric pressure, you are simply creating a lower pressure area for the fluid to move to.

    You could devise an experiment. Use a vaccum pump on the end of the straw, this will ensure the "ideal" low pressure area. The straw will also work better at sea level,(or lower), because of greatest pressure differential.

    Sea level pressure is roughly 14.7psi, in an "ideal" situation, this is what you have to work with. Now the question becomes.....

    For a given diameter straw,(smaller diameter is better), how high will 14.7psi lift a water column?


    A similar, but perhaps inverse, example of this problem is,

    Could you sit on the bottom of a 12 foot deep swimming pool, and breathe through a 13 foot garden hose "snorkel"? The answer is no.
     
    Last edited: Oct 1, 2009
  10. Oct 1, 2009 #9
    I made the point above that oral suction is not the same as inhaling. It's not the inverse of this problem.
     
  11. Oct 1, 2009 #10

    russ_watters

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    Yeah, with those numbers it depends on the particulars of the problem. It is close.
     
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