Brain teaser
#81
Again, airflow through the engines is completely different from airflow over the wings. One generates thrust, the other lift. There can only be thrust on the treadmill. Lift requires speed relative to the ground.
I didn't go through ground school for nothing.
#93
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Air moving through the engine causes the engine to generate thrust, thus causing the engine to move forward relative to the surrounding atmosphere. Since the engine is rigidly coupled to the wing, then the wing will also move forward with respect to the aurrounding atmosphere.
Lift does not require speed relative to the ground, it requires speed relative to the air. This is why all critical velocities (Vr, Vs, Vfe-x, Vne, etc) are always given in KIAS (knots indicated airspeed).
A Cessna 172, if I remember correctly, will rotate at around 60 KIAS, and experiance best climb at about 80 KIAS. So let's say that N6066R is sitting on the ramp, tied down loosely. A hurrinane begins to blow, and the airplane is oriented such that it is facing into the wind. When the wind speed reaches 60 knots, the airplane will rotate. By the time the wind gets up to 80, the airplane will be completely off the ground, doing it's very best to climb against the ropes.
In essence, it will by flying with zero groundspeed.
Which is totally irrelevant to the question, since the hypothetical airplane will in fact have both airspeed and groundspeed. Its groundspeed relative to the treadmill will be twice its groundspeed relative to the real ground, but it'll still be moving.
Again, the important part of the original puzzle, and the one that everyone seems to be overlooking, is that the treadmill speed is servo-locked to the speed of the aircraft relative to the stationary external reference, NOT whatever speed is necessary to keep the aircraft stationary.
It just occured to me that all those folks who have been accused of post-whoring to get up to 10 and be graned PM abilities should be eating this thread alive.
#96
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The plane and carrier move together. There would be no difference in Vcarrier and Vaircraft. This is a different situation.
If you were to explore this arguement, you'd also have to look at the fact that the earth is moving.
If you were to explore this arguement, you'd also have to look at the fact that the earth is moving.
#98
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Consider what would happen if, with the engine off, we start the treadmill rolling backwards at 5MPH and fix it at that speed. Since the airplane is not generating any thrust, it will remain stationary with regard to the treadmill, and thus begin to move backwards at 5MPH relative to the fixed point of reference.
Your argument was otherwise convincing, but this is a contradiction.