Are y'all really still talking about this? This is 2012, not 2002. . . . Plane gets its energy from the propeller. . . how you answer the question is just semantics garbage about how you interpret the question. . .
It's one thing to interpret the question, but it's quite another to answer the question as it was presented. That's where the monkey wrench is, stuck in a vacuum port. via rubber ducky
7 years and 108 pages. Gotta love it. Summary- the question as written leaves a door open for a lot of assumptions and interjections not stated in the original question. Look at it this way. If it were a car AND "The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation", Read very slowly the words again " MATCH THE SPEED OF THE WHEELS AT ANY GIVEN TIME". Would or could the car move forward if the speed of the wheels matched the speed of the conveyor belt at any given time?
Why not simplify - the conveyor is set up to compensate for forward thrust from engines as well as wheel rotation. Would it fly then?
Since the wheels have bearings the conveyor could NEVER compensate for the thrust. That's the point of our argument. GT
A car couldn't because propulsion comes from those same wheels. A plane can because wheels are independent of the propulsion. They just help with the friction, skids on a plane can still take off from pavement, just a bunch of friction. Wheels locked thus conveyor isn't moving can still skid forward and take off.
Simple question. The speed of the conveyor will match any forward propulsion the aircraft can generate, as long as the tires are in contact with the conveyers belt, thus the aircraft maintains its relative position and never gets any airflow over the wings which is required for lift. Now if the aircraft could go faster than the conveyer belts speed than the aircraft could " fly", but not in the parameters of this question.
The original post said "...match the speed of the wheels", not the speed of the airplane. So, when the plane is traveling 50MPH, the conveyor will travel at 50MPH in the opposite direction. But, the airplane doesn't know or care how fast the wheels are traveling. GT
In the words of the immortal Sheldon Cooper Bazinga! GTH "But, the airplane doesn't know or care how fast the wheels are traveling. " Again read very very very slowly the orignal statement- quoted below. "The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation". Yes, it is impossible but within the confines of the original statment with "The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation", would a car or airplane have the ability to produce any forward motion?
What the heck does a moving runway have to do with speed that is established by a screw in the air? GT
For those of you that think it will take off have a look at the cause of the "Munich Air Disaster" http://en.wikipedia.org/wiki/Munich_air_disaster The relevant part is the "Investigation" paragraph and in particular: Whilst trying to take off from a slippery runway is not quite the same as the imaginery travelator it does illustrate the wheels gripping the floor play a vital part in moving the aircrft forwards at enough of a rate to achieve take off speed.
When I looked at the question, I saw a manual gearbox in my mind. I thought about two gears the same size in contact with each other. Both gears, regardless which one is the driven gear, will both turn at the same rotational speed. So, if an airplanes wheels, sans the remainder of the airplane, was in constant contact with a conveyor belt and you applied motion to either the belt or the wheels, the relative position between the conveyor and the airplane would remain fixed and constant. As in a manual gearbox, if one gear was larger than the other, and power was applied to the smaller gear, the larger gear would get farther and farther away from the other,but the rate all depends on the ratio between the two gears. I hope this is easier to understand than my first answer. I welcome your critique, I am always trying to learn something new. Tony
The only information one can get out of this statement is that there is no slip between the wheels and the conveyor belt. Nothing else! Let's have a look at the following two cases: 1) Imagine a plane that is flying above a runway (=conveyor belt at standstill) at a constant speed. The plane touches down. What happens? At the very moment of contact there is slip (wheels smoke when planes touch down!), because of the wheels inertia, but the wheels speed up until they match the speed of the runway. No slip. No smoke anymore. Plane still moving. 2) Imagine a plane that is flying above the conveyor belt at a constant speed. Now you've got the conveyor belt running in the opposite direction at the same amount speed. The plane touches down. What happens? At the very moment of contact there is slip, because of the wheels inertia, but the wheels speed up until they match the speed of the conveyor belt. No slip. No smoke anymore. Plane still moving. What's the difference between those two cases? The speed of the wheels after touch down. If the amount of speed of the conveyor belt is the same as the speed of the plane in opposite direction, the wheels will spin at twice rpm compared to the runway case (=conveyor belt at standstill). The conveyor belt needn't run at the exact speed of the plane in opposite direction. It could run at any given speed! That's the point! It would only effect the wheels' rpm as they can spin freely. E.g. it could run at the same speed of the plane in the same direction. Result would be zero rpm at the wheels. Or it could run even faster than the speed of the plane. In this case the wheels would reverse their rotation. We can neglect the amount of kinetic energy that is transformed into heat at the moment of touch down. If we couldn't do that and the plane would come to a standstill at the moment of touchdown (= the case of the non moving plane on the conveyor belt you predicted!) all the kinetic energy of the plane would be transformed into heat at this very moment. Neither the passengers nor the plane itself would survive if this was the case. The deceleration of the plane would be infinite!
I heard wheels don't work great in slush or snow, bunch of friction there. How about skis? How fast do those skis rotate?
This thread really belongs in P&R. The lack of basic understanding displayed here by those that think the plane won't fly borders on a fanatical religion. The "question" is irrelevant. Nothing that happens at the (free-spinning) wheels will make the plane stand still.
I am not going to read 110 pages of explanation here, so I apologize if this is a repeat. Assuming the conveyor belt is free wheeling. A plane sits on the end of the runway, wheels not rotating and the belt is also not moving. Pilot applies the brakes to the wheels and hits full engine power. The tires remain still (as in not rotating), but the conveyor with the plane sitting in it moves forward at a rate associated with the power applied. So the plane is moving forward, the conveyor belt is moving forward at the same accellerating speed, yet the tires are not rotating relative the the belt it is sitting on. So even though the tires are not moving relative to the belt beneath it, the axle (thus the plane) and the conveyor belt continue to accelerate through the air until the lift occurs. The wheel rpm is still zero at takeoff, and the belt relative to that wheel is also zero. So the "speed" of the wheel rotation is zero yet the craft moves forward as the belt turns on it own axis. So it doesn't matter if the wheels speed is zero, 140mph in reverse of 1mil mph going forward (theoretically, of course), the plane will be forced forward when the engine power is applied. Is that clear as mud?
You keep talking about the pitot tube and I'm not sure how that applies. Are you just messing with people? Not being argumentative... I just can't tell. From memory you think that the plane won't move. You also mentioned before that it said "there is no wind" to which I responded but didn't get a response back. Just seeing what you are playing at man! GT
