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Homework Help: Pressure and Force

  1. Nov 21, 2008 #1
    1. The problem statement, all variables and given/known data

    "A lid is put on a box that is 10 cm long, 16 cm wide, and 8.0 cm tall and the box is then evacuated until its inner pressure is 7.2e4 Pa."

    How much force is required to lift the lid at sea level?

    2. Relevant equations

    I know that I have to use P=F/A
    I changed my centimeters to meters also, although I'm not sure you have to.

    3. The attempt at a solution

    I used F = PA
    F= (Atmospheric pressure - inner pressure)(lxw)
    F=(100000 - 72000)(.10x.16)
    F=448 N

    I tried this answer but got it wrong. Can someone please point me in the right direction? Thanks!
  2. jcsd
  3. Nov 21, 2008 #2
    I figured it out! I just used a more accurate number for my atmospheric pressure instead of simply 10000.
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