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Fluid in hypodermic needle

  1. Nov 18, 2007 #1
    What force on the plunger would be needed to push fluid into a vein where the gauge pressure is 18 mm Hg? Answer for the instant just before the fluid starts to move.

    I know i need the density of mercury (in Meters) and that equals = 13.534e-3 / 100 which is

    1.3534e-4 for the density

    Next i did the conversion of the atm pressure of mercury and got 133 n / m2. (i think thats correct)

    ok so i know i need to use pascals and i developed my equations i was given and ended with

    F1 = P1/ A1

    Which is

    Density mercury * atm pressure mercury * 9.8 / pie * D^2

    I think that is the correct equation and when i use it i get the wrong answer.

    What im really stuck with is what i use as the diameter.

    Any help would be great if i messed up any conversions and what not. TY
  2. jcsd
  3. Nov 18, 2007 #2
  4. Nov 18, 2007 #3
  5. Nov 18, 2007 #4
  6. Nov 18, 2007 #5
  7. Nov 18, 2007 #6
    last attempt..
  8. Nov 18, 2007 #7
    sad panda
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