Re: Airplane on a treadmill
I think I got it now. Tell me if this isnt true using a boat and not a plane. Lets say a boat has to be going 20 mph to plane out. the boat is going up river into a rapids going 20 mph also. I say the boat would have to trottle up to 40 mph to pull up and plane out. right?
no because a boat planes out based upon it's water surface speed. So if the rapids are flowing at 20mph and the boat is headed upstream, it would plane out at 20mph relative to the water, which would be 0mph relative to the shoreline.
The same thing occurs with a plane and the air (not the ground). So how fast does any plane need to fly to stay airborne? It could be airborne at 0mph ground speed if the wind is strong enough (such as in a hurricane).
To transfer that to the treadmill, if the plane is powered off, and the treadmill starts moving, the plane will stay stationary relative to the ground. The only reason it would move backwards, would be due to friction in the wheel berrings (objects in motion/objects at rest, remember that stuff?), which for this excercise were said to have no friction. Now this whole thing is also assuming that there is no wind. Assuming all of that, when the plane's prop turns, it pulls the plane forward through the air, which also starts forward motion relative to the ground since the air and ground are both assumed to be stationary. So now you see how the whole thing works, once the plane gets up to take off speed, it takes off like normal.
Of course that could never happen in real life because there are annoying little things like friction, wind, etc that get in the way... although to be honest, most planes could easily overcome the friction caused by the treadmill running at 50-100mph. But this is a hypothetical question and situation, and should be treated as such.
