Quote:
Originally Posted by ken0042
I guess my thinking is that if the plane needs to hit 100 knots to take off, and the treadmill is going at 100 knots, the plane will now require a ground speed of 200 knots to take off.
And looking at the plane in the picture, I'm not sure it is capable of reaching a speed of double its takeoff velocity; be it ground speed or air speed.
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Ground speed means nothing to an airplane, airplanes can fly with zero ground speed. The only thing that matters with respect to being able to fly is airspeed.
In a way you are right, if the plane needs 100 knots airspeed to take off, and the treadmill is going 100 knots, the plane WILL require a "treadmill speed" of 200 knots to take off, but it will still only need 100 knots of air speed.
And the amount of energy required to reach 100 knots won't change by much, it isn't going twice as fast relative to what matters; the surrounding air. It will take a little more energy to overcome the friction of the wheels spinning twice as fast though.