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Air pressure

  1. Oct 28, 2011 #1
    1. The problem statement, all variables and given/known data
    A lid is put on a box that is 14 cm long, 12 cm wide, and 8.0 cm tall and the box is then evacuated until its inner pressure is 9.0 104 Pa.

    How much force is required to lift the lid in Denver on a day when the atmospheric pressure is 67.5 kPa (2/3 the value at sea level)?


    3. The attempt at a solution

    (67500-90000)*.o168
    =-378 N

    I Keep getting my answer wrong could someone help please
     
  2. jcsd
  3. Oct 28, 2011 #2

    gneill

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    Staff: Mentor

    Can you clarify that pressure value?
     
  4. Oct 28, 2011 #3
    the pressure value is 90000 pa
     
  5. Oct 28, 2011 #4

    gneill

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    Staff: Mentor

    9.0 104 Pa is 67500 pa ???

    Is it supposed to be 9.0x104 Pa ?
     
  6. Oct 28, 2011 #5
    Yeh I messed up my bad sorry
     
  7. Oct 28, 2011 #6

    gneill

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    Staff: Mentor

    Okay, then your working seems fine. What does it mean if the pressure outside is now less than what the pressure in the box is (or was!).
     
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