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Homework Help: Pressure temp volume

  1. May 11, 2012 #1
    1. The problem statement, all variables and given/known data

    i am just reviewing for a test and doing some practice questions. i disagreed with one of the answers and now i am uncertain about the relationships between pressure volume and temp. i thought the relationships were:

    as pressure increases, temp increases, volume decreases (any combo of these three)
    as pressure decreases, temp decreases, volume increases (any combo of these three)

    and just incase these are correct and maybe im interpreting the question wrong, the questions is basically given a picture of piping varying in size, at which point in the pipe is the water under the least pressure.

    i thought i would be at the point of largest volume, but the answer according to my teacher is a point with the least volume.
  2. jcsd
  3. May 11, 2012 #2


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    Staff: Mentor

    Is the water stationary or moving? Water is essentially incompressible so it doesn't behave like a gas with regards to pressure and volume, and volume versus temperature change is pretty small as long as it remains liquid. For moving gases or fluids the pressure is related to the velocity; you need to be concerned with Bernoulli's equation.
  4. May 12, 2012 #3
    according to the solutions sheet, the pressure is at its lowest at the thinnest part of the pipe, i thought it would be at the widest part of the pipe (greater diameter).

    and yes the water is moving
    Last edited: May 12, 2012
  5. May 12, 2012 #4


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    Staff: Mentor

    Search google images for venturi meter
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