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Homework Help: Problem using Gay-Lussac's law and forces

  1. Jan 2, 2010 #1
    1. The problem statement, all variables and given/known data
    A cubic box of volume 4.0 multiplied by 10-2 m3 is filled with air at atmospheric pressure at 20°C. The box is closed and heated to 160°C. What is the net force on each side of the box?

    2. Relevant equations

    3. The attempt at a solution
    So we can assume that volume is constant because the box is closed. P1=1 atm P2=unknown
    T1=20C T2=160C. Using the above equation I got: 1/20=P2/160--> 1/20*160=P2-->P2=8 atm
    Then to find the force I thought I should use F=PA. I converted 8 atm into N/m2 and got 810 600N/m2. For the area of one side of the box, I thought that one length of the cubic box was the cube root of 0.04 squared which I found to be 0.11696m2. So then, I put those numbers into the equation and got F=PA--> F=0.11696*810600--> F=94808.35N
    But this was wrong

    I have tried this problem many different times and keep getting it wrong. I was wondering if it matters the units you use for the first equation P/T=P/T. I thought as long as you kept them constant it didn't...but then when I tried it with different units eg. Kelvins instead of degrees Celsius I got a different answer.

    Could someone please help? I would really appreciate it!
    Thank you
  2. jcsd
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