Can this airplane take off?

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gtrietsc said:
Just when you think people can't get any dumber....

A plane flies by air moving over its wings. You can have the wheels spinning as fast as you want on a treadmill, but no air is moving over the wings. Therefore it will never take off. The treadmill actually counters any air movement.

Think about it. If it would work, why havent we retrofitted all our aircraft carriers with this incredible idea?

I have seen tuna sandwiches smarter than some people in this, the worst of all internet debates of 2007.
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You just qualified. A jet engine is not bound to the wheels, they just stop it from dropping, all movement is carried out with AIR, not GROUND. Explain how a TREADMILL can counter AIR movement. (Treadmill, not windmill)
 
Someone please lock this thread quickly!
 
If you somehow made the treadmill keep the plane in the same place, it could still technically take off. You would just need a very fast head wind.:p
 
Meh, not bothering to read everything that was posted here, but feeling like I need to say something :)

Keep in mind that this is not a physical problem. If the airplane make ANY movement with wheels on the belt, speed of wheels and the tunway will instantly reach infinity, or the condition of runway matching the speed won't hold.

If you want to neglect that - sure, it'll fly...
 
This is crystal clear: It can take off! You don't even necessarily need wheels at all on a plane. Think about planes that start and land on water. Like other said: The propeller or turbine makes the plane go fast and reach takeoff speed, not the wheels...

It's pretty scary how fast people get offensive in this thread. Not good.
 
There is no need for this thread to exist as this was done to death a while ago.

/The plane will take off
//Plane wheels don't move the plane
///End.
 
The real question is: If a tree falls in a forest and nobody is there to hear it, does someone really need to ask a hypothetical but pointless question in this forum again in the hope that the entire universe will disappear up its own arse in a puff of logic?
 
mods, please lock this thread.
And remind the people who haven't taken high school physics that they still need to respect the rules of the forum.
 
watto said:
There is no need for this thread to exist as this was done to death a while ago.

/The plane will take off
//Plane wheels don't move the plane
///End.
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Oh not this thread again.

ralph02.gif
 
watto said:
/The plane will take off
//Plane wheels don't move the plane
///End.
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But, but... What will happen to the wheels? They stand on the treadmill, they have infinite grip, treadmill is preventing them from moving. Wheels are attached to the plane. If wheels don't move - plane doesn't move. Plane doesn't move - plane doesn't fly :p












/Once again, this is a thought experiment, and a paradoxical one on top of that. It was fun watching the debate for the first time, until you realize that solution will not be found. And then it happens again on the next forum :)
 
I would guess the plane can't take off. It doesn't matter what drives the wheel, as long as the wheel spins in one direction, it'll be countered by the treadmill, so even when the jet engine can make enough thrust to push the plane to 30mph, if the plane has not leave the ground, the treadmill will spin in the counter direction at 300mph, so no air will move under the wings, so there's no lift.
 
This is such an old Engineering question, its been in the nytimes, boing boing and etc.
And the problem with the question is how its asked, and described. First, for a plane to take off it must have air speed passing over and under the wings for lift to be created.
When we think of a treadmill, its the idea of moving your legs and staying in one place. Same would go if you put a car on a rolling road and etc. They just stay in one place.
So if the plane does not move, it will not take off. Thats it. Now the question is because the plane is powered by jet engines not by its wheel, then it will take off. Wrong. The wheel allow the aircraft to roll and apply opposite force to the ground. When you negate that force, the plane will just stay in place. The aircraft will not move, and no take off. But again it all depends on how the treadmill works, if it can sense the wheel movement and apply the same exact force in the opposite direction.
 
MXM said:
But, but... What will happen to the wheels? They stand on the treadmill, they have infinite grip, treadmill is preventing them from moving. Wheels are attached to the plane. If wheels don't move - plane doesn't move. Plane doesn't move - plane doesn't fly
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There always are some nice analogies in these discussions. so here's one for you.

You're riding a bike on a treadmill, which automatically matches your speed. So whatever you do, you will not move in respect to the floor surrounding the treadmill, right?

Okay, now you take your feet off the pedals and put on a rocket backpack, which means you are pretty much the same as a plane (wheels for rolling, rocket thingy for propulsion). When you fire up the rocket backpack, it'll push your forward, right? But the treadmill will start going backwards, cause it tries to match your speed. But you're not pedalling anymore, so you won't care about what the bike beneath your does. And for that very reason, you will move forwards, such as a plane would on a conveyor belt.

Zuhaib said:
When we think of a treadmill, its the idea of moving your legs and staying in one place. Same would go if you put a car on a rolling road and etc. They just stay in one place. So if the plane does not move, it will not take off. Thats it. Now the question is because the plane is powered by jet engines not by its wheel, then it will take off. Wrong. The wheel allow the aircraft to roll and apply opposite force to the ground. When you negate that force, the plane will just stay in place. The aircraft will not move, and no take off. But again it all depends on how the treadmill works, if it can sense the wheel movement and apply the same exact force in the opposite direction.
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Not quite. What you're suggesting is that the treadmill is able to transfer a counter force onto the plane and prevent it from moving. But the treadmill can only apply a counter force on the wheels of the plane. You're right in saying that the wheels are connected to the plane. What you left out of the equation is that the wheels can move freely and independently forwards and backwards, so by spinning the wheels, the treadmill will not apply any force on the fuselage.
 
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I've just figured why the plane wouldnt be pushed back by the conveyor belt. Provided there is zero friction between the bearings, the reverse rotating conveyor belt cannot exert force on anything except the wheels, while it is rotating backwards. This means, the only thing it can do is spin the wheels.
 
the Interceptor said:
Okay, now you take your feet off the pedals and put on a rocket backpack, which means you are pretty much the same as a plane (wheels for rolling, rocket thingy for propulsion). When you fire up the rocket backpack, it'll push your forward, right? But the treadmill will start going backwards, cause it tries to match your speed. But you're not pedalling anymore, so you won't care about what the bike beneath your does. And for that very reason, you will move forwards, such as a plane would on a conveyor belt.
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I fully understand what are you trying to say, but you can't just say "you don't care" if you're doing a physical analysis. And that is the whole point of this problem, it gives you different answers depending on what direction you look at it from. I'll chew it out while I'm in the mood :)

Continuing with your analogy - what will be the speed of the pedalbike wheels relative to the ground? It should be equal to your speed relative to the ground, since you're still sitting on the bike, and for the sake of accurate analogy, you can't leave the bike.

Wheel that is moving forward on the treamill MUST have higher speed than the treadmill itself if it has grip.
Treadmill matches this higher speed of the wheel.
But you have external force moving the wheel, making it even more faster than the treadmill.
But treadmill must follow the speed of the wheel by definition, so speed increases once again.
This continues to the infinity.

See the conflict? To move even a millimeter, speed of the wheel must be higher than speed of the treadmill, but speed of the treadmill must be equal to the speed of the wheel. You can't move because moving would... make you stationary.

You can even go as far as simplifying this problem to: can you move an object with wheels AT ALL if it sits on the treadmill bla bla bla... using ANY external force.

Physically this is impossible, because reaction can't possible happen at the precisely the same time as action, and of course you can't make wheels spin at infinite speed.

But as a thought experiment I'll stay at the "not flying" camp. Engine blasting off can move the air or the whole damn universe, but this treadmill is not going anywhere relatively to the plane bacause that's the condition of the problem.
 
Oh what the hell, let's go on.

When the run way senses the wheels moving, the run way will move match the speed of the airplane's wheels but in the opposite direction
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Ok, if it senses something, it means that something has already happened! If nothing happened, there can't be any detection of it. So - delay exist, even if differentially small.

If delay exists, wheels can move forward for this differentially small period of time before treadmill catches on.

-> Wheels CAN MOVE!

It'll fly! Hooray!
 
MXM said:
Continuing with your analogy - what will be the speed of the pedalbike wheels relative to the ground? It should be equal to your speed relative to the ground, since you're still sitting on the bike, and for the sake of accurate analogy, you can't leave the bike.

Wheel that is moving forward on the treamill MUST have higher speed than the treadmill itself if it has grip.
Treadmill matches this higher speed of the wheel.
But you have external force moving the wheel, making it even more faster than the treadmill.
But treadmill must follow the speed of the wheel by definition, so speed increases once again.
This continues to the infinity.
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This is true, and for that very reason, I'd have asked the question a tad differently, but much easier in the end result.

Anyway, what would happen in real life is that the moment you start the experiment and move a tad, the wheels and the treadmill would accelerate up to a point where some mechanical component fails, and you'd end up with a saddle up your bottom. :lol:

MXM said:
See the conflict? To move even a millimeter, speed of the wheel must be higher than speed of the treadmill, but speed of the treadmill must be equal to the speed of the wheel. You can't move because moving would... make you stationary.
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Okay, for the sake of this thought experiment, let's say we're working with "optimised physics" and indestructible components here. Now, I get what you're saying in terms of the speeds we must consider here, but I think you're mixing some speeds that shouldn't be mixed.
What you say is that you actually can not move in regards to the surrounding floor (which, as we all agree, is neccessary for a plane to take off), because it would be contradictory to the stats of the experiment. But actually, I don't see a problem here. Let's think of this from another point of view.

We have an external source of force here, the rocket backpack. It pushes me forwards. The treadmill however tries to hold me back by spinning backwards. It doesn't match my speed however, rather than the speed of the wheels of my bike I am simply sitting on. Now, as I move forward, the treadmill will increase counter-acceleration to try to hold me up. Nonetheless, the only effect is that the treadmill will accelerate harder. Given that the components will not fail, I will still move forwards. Understanding that the wheels below me do not apply any force on my movement on the bike, the amount of counter speed and counter acceleration of the treadmill will have no effect on me.
 
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