Quote:
Originally posted by Mobycat:
Quote:
Originally posted by MattyX:
[b]Sure, the boat doesn't need lift, but you said the propellor pushes it, and you're right. The plane doesn't need lift to move forward, just to fly. It can move forward, though, and increase its airspeed enough to attain lift, no matter what the conveyor does.

::edited for grammar::
Put that same boat in a river. Trying to go UPstream. If the stream is matching the speed of the propeller...no movement.[/b]
Ah, but that is an erroneous analogy. The overhead conveyor plays exactly the same role as the conveyor in the first problem. You said yourself earlier (essentially) that planes like to take off into the wind (with a headwind), so assuming that there would be, say, ten knots headwind or headwater. That value being constant, any equal and opposite force would keep a craft (air or water) stationary. That would mean ten knots of airspeed or waterspeed. once the power of the craft overcomes the headwind/water, the craft moves forward, regardless of what the conveyor might do.