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Homework Help: Weight of a plane

  1. Nov 2, 2006 #1
    An airplane flies on a level path. There is a pressure difference of 525 Pa between the lower and upper surfaces of the wings. The area of each wing surface is about 128 m2. The air moves below the wings at a speed of 81.5 m/s. Estimate (a) the weight of the plane and (b) the air speed above the wings.

    Fup = PA

    F=525*128=67200 N
    67200 = m(9.81); m=6850.153kb

    It weighs 67200 newtons doesn't it?

    also, I am unsure how to begin part b - any ideas? Thanks
  2. jcsd
  3. Nov 2, 2006 #2
    for b u use bernoulli equation and throw the pressure to one side.u will notice that is P1 - P2 and thats ur 525 Pa
  4. Nov 5, 2006 #3
    hmm, to use bernoulli's equation I need:


    I don't have initial pressure, final pressure, the height, or any way to calculate V above the wings.... I guess I'm unsure how to solve with so many unknowns??
  5. Nov 5, 2006 #4
    any ideas? This one sure has me confused...
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