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G Force question

  1. Oct 25, 2005 #1
    A friend of mine likes to e-mail me a question of the day. I need a little help on this one.

    When you close the canopy on your aircraft you notice there is a fly inside. You then takeoff and get up to altitude. The fly is flying inside the cockpit when you put 5 Gs on the aircraft - question - is the flying pulling 5 Gs too? And, if not, will the fly splatter against the windscreen as you pull 5 Gs?
    Last edited: Oct 25, 2005
  2. jcsd
  3. Oct 25, 2005 #2
    Im assuming you're asking pulling positive 'g's and not negative. In that case, the fly would smash into the floor of the aircraft, for the same reason that your rear end gets smashed into the seat when you pull the g's. Accleration forces in the positive range cause the aircraft to 'accelerate', thus the fly who is flying his own flight would meet the aircrafts floor.
  4. Oct 25, 2005 #3


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    Staff: Mentor

    To help clarify, let me provide another example: a helium balloon that is at equilibrium with the air in the cockpit (not rising to the top or falling to the bottom). Since it weighs exactly the same as the surrounding air, pulling g's would not affect it.

    But a fly weighs more than the surrounding air. It's flapping it's wings to create lift equivalent to it's weight. When the plane pulls 5 g's, the fly's weight goes up 5x and it falls to the floor unless it can beat it's wings faster.

    Welcome aboard, both of you.
  5. Oct 25, 2005 #4
    i dont understand, because you guys are saying the fly meets the ground when you are "pulling" 5gs i dont uderstand why the fly hits the ground would he be pushed to back if you were accelerating forward, or maybe you are not acceleration forward you are pulling up causing the increase in gs.

    i dont know.........
  6. Oct 25, 2005 #5
    When you "pull g" in an aircraft what you are doing is changing the straigh flight path into a curved flight path upwards. So when the aircraft is following that curve, Newton has ordered that things, not forced to do something else, to continue moving in a straigth line. So that straight line of the fly eventually meets the cockpit floor in its curved path upwards.
  7. Oct 25, 2005 #6
    Thanks to all for your help.
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