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Homework Help: What stress needs to be exerted to turn a quart of water into a pint?

  1. Apr 14, 2012 #1
    1. The problem statement, all variables and given/known data
    Dr Stewart’s Aunt Sally was constantly reminding him that he couldn’t squeeze a
    quart (946 ml) into a pint pot (473 ml). Annoyed by this negative attitude, he set
    about proving old Sally wrong. He constructed a platform, resting on a steel piston
    radius 1 mm, length 10 m, bearing down on a chamber of equal radius, containing
    1 quart of water. He then placed a number of 1000 kg elephants, procured from the
    local zoo, on the platform.
    What stress needs to be exerted to turn a quart of water into a pint?

    2. Relevant equations
    stress = F/A

    3. The attempt at a solution


    Not really sure what to do from here...
  2. jcsd
  3. Apr 14, 2012 #2


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    Gold Member

    Hope that the zoo has a lot of elephants available. Water is very nearly incompressible. You are looking at a 50% reduction in volume which is going to require extreme pressure, very extreme pressure!
  4. Apr 14, 2012 #3

    D H

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    Staff Emeritus
    Science Advisor

    Do the math. Not even one elephant is needed. And these are small elephants.

    That's assuming this piston or cylinder could exist. Both would have to be made of unobtanium.
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