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Homework Help: How much force will be required to remove the lid?

  1. Nov 21, 2008 #1
    1. The problem statement, all variables and given/known data
    An airtight box has a removable (massless) lid of area 4·10-2 m2. A lid is placed on it while it is on top of a mountain (where Patm=0.81·105 Pa). It is then taken to sea level, where Patm = 1.013·105 Pa. How much force will be required to remove the lid?

    2. Relevant equations

    3. The attempt at a solution
    For the first part:
    F=PA=.04 x 81000=3240 N
    For the second part:
    F=PA= .04 x 101200=4052 N

    is there a change in pressure type of equation?
  2. jcsd
  3. Nov 21, 2008 #2


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    Science Advisor
    Homework Helper

    Re: Pressure?

    You are only interested in the change of pressure. - this gives you the pressure differnce between the inside and outside of the box and so the force to open it
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