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Pressure on a submarine window homework

  1. Sep 17, 2009 #1
    1. The problem statement, all variables and given/known data

    A research submarine has a 40.0 -diameter window 8.30 thick. The manufacturer says the window can withstand forces up to 1.00×106 . What is the submarine's maximum safe depth?

    2. Relevant equations
    p=Po + pgh


    3. The attempt at a solution
    p = 1.01x 10^5 + ? X9.8 x 8.3

    i dont know how to find that p since we were not given mass
    please helppp i am so confused of what to do
     
  2. jcsd
  3. Sep 17, 2009 #2
    Hint: Pressure on the outside = Pressure on the inside, at max depth. Pressure on the outside depends on the density of the water, air pressure and depth. Pressure on the inside at max depth equals air pressure and strength of the window.

    Note that it was a long time since I did this so I'm a little unsure
     
  4. Sep 17, 2009 #3

    Doc Al

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    Staff: Mentor

    That equation is:
    Total Pressure = Atmospheric pressure + density*g*depth

    What's the density of water? (You don't need the mass of anything.)

    First figure out what pressure is needed to break the window. How does pressure relate to force?
     
  5. Sep 17, 2009 #4
    p= F/A
     
  6. Sep 17, 2009 #5
    The pressure inside the submarine is maintained at 1.0 atm
    do we ignore that fact
     
    Last edited: Sep 17, 2009
  7. Sep 17, 2009 #6
    The pressure on the inside of the window is air pressure + something else, the "something else" has to do with the window.
     
  8. Sep 17, 2009 #7

    Doc Al

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    Staff: Mentor

    So use the given information to figure out the pressure that would break the window.
    The question is ambiguous. "The manufacturer says the window can withstand forces up to 1.00×106 ." doesn't specify whether that is the net force or just the outside force.

    I would pressume they meant the net force. (So ignore atmospheric pressure since it's canceled by the inside pressure.)
     
  9. Sep 17, 2009 #8
    in other words we have to find the outer pressure or is that the atmostpheric pressure, so what happens afterwards, i am not sure is that the atmostpheric pressure?
     
  10. Sep 17, 2009 #9
    then it becomes
    Total pressure = 101.3+ (9.8 X d X 1000)

    =101.3 + 9800d

    and now my question is , how do i get my value for d?
     
    Last edited: Sep 17, 2009
  11. Sep 17, 2009 #10

    Doc Al

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    Staff: Mentor

    What's the 101.3?

    You'll solve for it. The pressure is not an unknown; you can figure it out from the information given about the window.
     
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