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Conceptual problem regarding pressure and surface area

  1. Nov 16, 2014 #1
    Is the air pressure acting on the top of the head of a person standing in a room equal to the air pressure acting on a same area on the floor of the same room?

    Since F = pA , it seems as if the air pressure is independent of the height of the surface on which it is acting. But that doesn't seem to make sense because the force on the ground must be due to the weight of the air above the person's head plus the weight of air between the head and the ground?

  2. jcsd
  3. Nov 16, 2014 #2


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    Technically, you are correct, there is a pressure difference. However, that pressure difference is small in comparison to the total atmospheric pressure.

    It is this pressure differential that provides a buoyant force to, for example, helium balloons.
  4. Nov 16, 2014 #3

    Doc Al

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    That equation just defines pressure in terms of force and area. There's no implication that pressure is independent of height. (Height isn't even mentioned!)

    It's certainly true that pressure varies with height. That's what creates the buoyant force on an object (or person).
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