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Vacuum Physics?

  1. Jan 20, 2010 #1
    Vacuum Physics???

    I would like some clarity on a problem I think is attributed to a vacuum space. This is what happened...I have a small room that is 7' x 10', there are two metal doors directly across from each other on opposites sides of the room. It seems that when I want to close the door fast the air within keeps the door from closing but I can close it if I do it slowly. My problem is that my daughter slammed the door with significant force and it did close, however there are double pane windows in that room as well and one of the windows now has a crack in it (the inside side of the double pane glass---inside the room). Could the vacuum force when she slammed the door caused the glass to crack?
     
  2. jcsd
  3. Jan 20, 2010 #2

    stewartcs

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    Re: Vacuum Physics???

    A vacuum doesn't exert a force on anything.

    I presume the door opens outward? If so then it sounds more like air is being drawn/forced into the room by the closing door and thus creating an overpressure in the space.

    CS
     
  4. Jan 20, 2010 #3
    Re: Vacuum Physics???

    from my POV, that's quite a silly prediction, there's air in the room , the air pressure does not seem sufficient to break the panes though(the one who designed the room must know, decrease in the area of the pane and increase in the area of the room decreases the force on the pane), the force of the slammed door propogated through the walls
     
    Last edited: Jan 20, 2010
  5. Jan 20, 2010 #4

    stewartcs

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    Re: Vacuum Physics???

    The door slamming could certainly also cause the problem...but I imagine that the door would have to be slammed really hard to crack a pane of glass. I suppose it would help to know the composition of the room (e.g. walls, windows, doors).

    CS
     
  6. Jan 20, 2010 #5

    stewartcs

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    Re: Vacuum Physics???

    The air in the room is at atmospheric pressure, the air outside of the room is as well. If the pressure inside the room is increased enough, then the unbalanced air pressure on the inside could certainly crack the pane of glass. Hence, it's not that silly.

    CS
     
  7. Jan 20, 2010 #6
    Re: Vacuum Physics???

    My post was addressed to the OP. When I was doing it, there wasn't yours
     
  8. Jan 20, 2010 #7
    Re: Vacuum Physics???

    I doubt that the glass would crack, from the pressure. Glass is very stable and it is pretty much impossible to break it with an even force like a pressure wave of a few millibar. The force is very even. With double pane windows it is almost impossible since these already have lowered pressure in between the panes so they are build to withstand substantial pressure.

    When the glass breaks from the slamming of a door, it is most likely caused by vibrations, or fabrication defects. If the glass is mounted unevenly a pressure point might cause a crack, and once double paned glass windows get a crack they break over a large area, due to the pressure difference (I talk from experience). So yes slamming a door might break a window but not directly, only through shaking it somehow.
     
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