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  #21  
Old 03-04-2006, 08:21 PM
Paradoxic Paradoxic is offline
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Join Date: Mar 2006
Posts: 7
ground speed? DOH!

Quote:
Originally Posted by enipla
Letís say the airplane needs 100mph ground speed to take off...
This is what happens when you consider this as a thought experiment and not a physics equation. What if I've got a 100mph tail wind?

No airplane requires ground speed to take off. It requires airflow across it's wings of sufficient velocity to take off - or, to put it another way, it requires air speed, not ground speed.

The answer is not intuitive, and this fails as a thought problem unless you actually do the math.
  • Force generated by the engines directed in one direction.
  • Force generated by the treadmill in the opposite direction (how about a treadmill driven by the same engines as the plane uses?)
  • The forces meet and cancel out, at the wheel assembly (w/hot tires) and ground friction.