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Homework Help: Volume and Pressure Cylinders

  1. Feb 28, 2007 #1
    1. The problem statement, all variables and given/known data
    Problem comes straight from a 2001 AP Physics B test
    http://img151.imageshack.us/img151/6159/physicscylinderszq4.png [Broken]

    2. Relevant equations
    PV = nRT

    KE = 3/2KT

    deltaU = Q+W

    3. The attempt at a solution

    Okay, for the first two (a and b) I arrived at an answer of double the initial pressure of State 1 and half of the initial volume of State 1. This was because after I drew myself a little P vs. V graph, I knew the two States had to be on the same isotherm, so pressure had to increase in order for volume to decrease. Also, I just realized as I write this, if T is constant, in PV = nRT that means nRT is a constant and as P increases, V must decrease.
    I'm pretty sure that's right, if it's wrong, I would appreciate clarification.

    For c I got Isobaric, simply because isothermal and adiabatic do not work.

    For d I got Yes, 4 --> 1 is isobaric simply because I drew a P versus V graph and since it has to go back to the same isotherm State 2 was on, but volume had to decrease, it had to be isobaric.

    I do not understand e. I'm having a hardtime knowing what the weight does...do you have to use P = F/A?

    Thanks for any help at all on this, any corrections if im wrong and any elaboration on any topic is greatly appreciated.
    Last edited by a moderator: May 2, 2017
  2. jcsd
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