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Thread: Can this plane take off?

  1. #1
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    Default Can this plane take off?

    This has been all over the web, and has caused a lot of controversy.. and even a few lay offs..

    Here's the scenario...

    An airplane is on a conveyor. The conveyor is set to match the speed of the airplane in the backwards direction. However fast the plane moves, the conveyor moves just as fast.

    Can the plane take off?

    (yes, I know the answer to this, but a shocking amount of people do not)

  2. #2
    Cally
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    Default Re: Can this plane take off?

    I'd say no... because although the wheels are movement, it doesn't have enough momentum (force) to take off...
    But seeing as science is one of the subjects I hate most, I could be very wrong.

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    Default Re: Can this plane take off?

    I say no because the plane has to be moving to create the air pressure under the wings to cause lift. And lift is what makes the plane fly.
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    God/dess kitana's Avatar
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    Default Re: Can this plane take off?

    I say yes, but only if the plane would get up to top speed then slam on the breaks and be forced backwards then when it hopped off the treadmill, it went full speed forward.

    Either that or have it be a harrier, which can damn near take off like a hellicopter.

    Yeah I think really bizarrely sometimes, lol.
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    Featured Member MeganS's Avatar
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    Default Re: Can this plane take off?

    If the conveyor is working against the plane at the same speed, wouldn't everything be suspended right there? No liftoff/movement??
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    Default Re: Can this plane take off?

    No, the speed of the wheels (about the only thing moving in this example) is irrelevant, the air needs to move over the wings AND IN A FORWARD DIRECTION to fly

    the top curve of the wing (as opposed to the flater bottm) is designed to change air pressure above (lessen it) therefore creating lift. Unfortunately, wings don't work the same backwards.

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    Default Re: Can this plane take off?

    I'd say no because the plane would have no wind to give if lift under the wings. When you run on a treadmill do you feel wind hitting you like if you were really running in the park? I could be totally wrong though which would really suck because I used to fly and had to study a lot of stuff about wind and lift (not that I recall much of it).

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    Default Re: Can this plane take off?

    Well I keep thinking the wheels dont make the plane take off , the thrust of the jet engine does . I know it sounds like it would be on a kind of tredmil , there has got to be a trick , and I agree the plane needs speed then lift . I give up !

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    Default Re: Can this plane take off?

    yes absolutely the plane can take off ... although the wheel bearings will probably wind up being smoked by the extra RPM the conveyor creates.

    The key to this question is the fact that, unlike a car, there is no linkage between the speed of the wheels on a runway/conveyor and the speed of the wing through surrounding air. The propeller/jet is going to thrust the plane forward through the air, and when the 'airspeed' hits the minimum required to lift the plane, away it goes. The fact that the plane's wheels happen to be turning forward at 100mph, not moving at all, or turning backward at 100mph doesn't mean shit, since they are 'free wheeling' relative to the fuselage.

  10. #10
    AudreyLeigh
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    Default Re: Can this plane take off?

    I feel like the odd one out but...

    Even tho the conveyor belt is not letting the plane move forward the plane is still getting a lot of speed even tho technically its not moving... so...

    Plane gets enough speed for lift off just fine whether its moving forward or getting that speed from the same place...

    Yes - I think the plane can take off just fine from a conveyor belt.

    Edit: This is assuming the engines are on and everything... I dont see why the plane WOULDNT be able to lift... maybe Im wrong?

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    God/dess Deogol's Avatar
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    Default Re: Can this plane take off?

    Seems to me it would fly. It doesn't use the ground for anything but to rest upon (or hit.)

    It is similar to the question about how can a rocket fly in space when there is nothing to "push against." The fact is the force generated by the rocket pushes the rocket it's self.

    Interesting thought experiment.

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    Default Re: Can this plane take off?

    The plane won't be moving, if the plane don't move it can't fly. IF this conveyor belt theory worked we would not need runways.
    "The ultimate measure of a man is not where he stands in moments of comfort, but where he stands at times of challenge and controversy."

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    God/dess onlythebest's Avatar
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    Default Re: Can this plane take off?

    I say "no" because airplanes need wind energy (air drag) to help them take off.If there was an enormous fan in front of the plane,then it is still a big "maybe".
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    Default Re: Can this plane take off?

    Melonie is correct.

    Essentially the wheels and the conveyor belt have nothing to do with the propulsion of the airplane.

    Think of it like this, the airplane is on a runway covered in a layer of ice. The ice causes the wheels to spin or not move at all if the airplane is moving. An even better example would be is if the plane locked the wheels up and then fired up the engines, it would still move forward even though there is no friction between the wheels and the ground due to the ice.

    The conveyor belt situation is identical. As Melonie said, the propulsion is coming from external engines pushing against the air moving the plane forward. In a car, the engine turns the axis of the wheels and the friction of the wheels against the ground is what causes forward movement.

    Think of it step by step here. Imagine your car is on ice. You step on the accellerator and you go nowhere because the wheels are spinning. But now let's put a jet engine on your car. Your wheels can still be spinning but the car will no move forward. Jet engines do not push against the ground, they push against the air on the tail end of the engine to make it move forward. This is called "thrust". The wheels in this case have nothing to do with it and just like the ice, the conveyor belt serves the same (irrelevant) purpose.
    Last edited by DancerWealth; 12-08-2005 at 08:09 PM.

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    Default Re: Can this plane take off?

    Quote Originally Posted by DancerWealth
    Melonie is correct.

    Essentially the wheels and the conveyor belt have nothing to do with the propulsion of the airplane.

    Think of it like this, the airplane is on a runway covered in a layer of ice. The ice causes the wheels to spin or not move at all if the airplane is moving. An even better example would be is if the plane locked the wheels up and then fired up the engines, it would still move forward even though there is no friction between the wheels and the ground due to the ice.

    The conveyor belt situation is identical. As Melonie said, the propulsion is coming from external engines pushing against the air moving the plane forward. In a car, the engine turns the axis of the wheels and the friction of the wheels against the ground is what causes forward movement.

    Think of it step by step here. Imagine your car is on ice. You step on the accellerator and you go nowhere because the wheels are spinning. But now let's put a jet engine on your car. Your wheels can still be spinning but the car will no move forward. Jet engines do not push against the ground, they push against the air on the tail end of the engine to make it move forward. This is called "thrust". The wheels in this case have nothing to do with it and just like the ice, the conveyor belt serves the same (irrelevant) purpose.
    Excellent way to explain it and also the correct answer. The plane will indeed take off.

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    Default Re: Can this plane take off?

    What a way to make a person feel stupid,LOL!!!
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    Default Re: Can this plane take off?

    Quote Originally Posted by onlythebest
    What a way to make a person feel stupid,LOL!!!
    Na, don't feel dumb. The people here answered remarkably well, even those who were incorrect. On another board I visit, this question has had a combined 309 replies since the question was posed a few days ago. Even after the proper answer was given, the thread has kept going and as I read the newest replies on another browser window, people are still arguing lol.

  18. #18
    Cally
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    Default Re: Can this plane take off?

    Okay im not buying this answer. A plane needs momentum... in order for a plane to take off it needs airflow underneath the wings. Since the plane isn't moving through the air, its not going to take off.
    Really the plane is going to be just a treadmill... its not going anywhere.

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    Default Re: Can this plane take off?

    The plane will not take off. I've read the given explanation and I don't buy it.

  20. #20
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    Default Re: Can this plane take off?

    I know an airplane pilot.Me thinks of asking him what he thinks.
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    Default Re: Can this plane take off?

    Yes- the plane's still doing everything exactly as it would normally, it's just the ground underneath that's different- instead of it always being 'new' ground, it's the same stuff rotating.

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    Default Re: Can this plane take off?

    Quote Originally Posted by Cally
    Okay im not buying this answer. A plane needs momentum... in order for a plane to take off it needs airflow underneath the wings. Since the plane isn't moving through the air, its not going to take off.
    Really the plane is going to be just a treadmill... its not going anywhere.
    You're still thinking that the wheels and the conveyor belt have anything to do with the matter. They don't. Both are completely irrelevant. The thrust from the JET ENGINES is what is propelling the aircraft forward. Once the engines turn on, the plane gets forward momentum just as it normally would and the lift would then move the plane into the air just as it normally would.

    Again, you need to stop thinking that the wheels have anything to do with it. Imagine the brakes were on and the plane was on ice. it is the identical situation as the conveyor belt. Since there is no friction, the plane will move forward once the engines are on. The jet engines under the wings is what propels the plane forward not the wheels. As mentioned already, the wheel issue is 100% irrelevant.

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    Default Re: Can this plane take off?

    The plane's speed and velocity is measured by Air speed. The Car's drive engine depends on friction with the road, the plane's engine depends on forced air through the turbines. Once the plane overcomes the backwards velocity of the conveyor belt, the air-based engines will overcome the wheel force and boost the plane forward.

    Car engines create friction.

    Plane engines create airflow.

    Car engines are focused on the wheels.

    Plane engines are focused on the wings. <Not in all cases ok? Some in the front>

    The WHEELS have VERY little involved in the planes function beyond a contact point.
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  24. #24
    Cally
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    Default Re: Can this plane take off?

    LoL This drove my man nuts he just spent two hours looking and reading everything about it that he could find... in the end... yes it can take off. I never should have doubted Melonie! Ahaha...

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    Default Re: Can this plane take off?

    Quote Originally Posted by Mastridonicus
    Plane engines create airflow.
    I didn't realize that plane engines created airflow. It makes much more sense to me now.

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