1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Find work done on an isobaric system

  1. Feb 28, 2014 #1
    1. The problem statement, all variables and given/known data
    A 1kg box of Aluminum initially at 22C is warmed at P=1atm so that its T increases to 40C. Find
    a) The work done on the system


    2. Relevant equations

    W= -∫PdV

    3. The attempt at a solution

    The pressure is constant at 101,300Pa

    D=m/V

    So V=m/D

    D of Al at room temp = 2700kg/m^3

    Therefore

    [itex]W= -101,300Pa \frac{1kg}{2700kg/m^{3}}(1+24x10^{-6}(18))^{3}[/itex]

    Where ΔT=18 and 24x10^-6 is the linear coefficient of expansion of Aluminum.

    = -37.6J

    Not the right answer, it should be around 48mJ. I can't see what I'm doing wrong here.
     
  2. jcsd
  3. Feb 28, 2014 #2

    ehild

    User Avatar
    Homework Helper
    Gold Member

    Work is PΔV. What is the change of volume?

    ehild
     
  4. Feb 28, 2014 #3
    It should be

    [itex]W= -101,300Pa \frac{1kg}{2700kg/m^{3}}((1+24\times 10^{-6}(18))^{3}-1)[/itex]

    because you forgot to subtract the initial volume. Essentially the same result, which retains only the linear term, is:

    [itex]W= -101,300Pa \frac{1kg}{2700kg/m^{3}}(3)(24\times 10^{-6}(18))[/itex]

    Chet
     
  5. Mar 1, 2014 #4
    Oh yeah I totally missed that. Thanks.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Find work done on an isobaric system
Loading...