NationStates Jolt Archive

yeah, that emote seems appropriate. What you don't get is that the treadmill does NOT act "equal and opposite" to the plane's velocity (although as an aside, since velocity is a vector, it can not be both simultaniously equal and opposite, since velocity is direction dependant, something opposite will not be equal, though it can have an equal value).

The wheels on a plane are not connected to a drive shaft like they are on a car. If you take a plane, with the engine OFF, and drop it on a treadmill, it won't go anywhere. The treadmill will move under the wheels, and the wheels will just...spin. The wheels aren't connected to any drive shaft, them spinning won't move the plane. The treadmill will just cause the wheels of the plane to spin, but the plane, with it's engine off, won't move.

When the plane turns its engine on and begins moving forward, again, the treadmill will do nothing. A plane is not driven by its wheels, it is driven by its turbine. The wheels merely serve to reduce friction with the ground.
Why won't the plane, with no other force acting upon it, simply move with the treadmill? Why would the wheels begin spinning at all?

Helping thoughtstep:
Can a hovercraft take off from a moving runway ?no, because hovercrafts hover, they don't fly. of course the moving runway will not affect it. ;)

sorry, I mean, if the turbine engine on the plane was not active IE no force propelling it forward. Theoretically (IE without friction) a stationary plane without its turbines active will sit there, as the wheels spin. I don't think so. if the plane is idle, engine not running, no thrust whatsoever, I think it will move with the treadmill. once the engine is on and thrust is provided, then the treadmill won't affect it.

because weight will still be on the wheels and that would help provide the friction to keep the plane on the treadmill.

EDIT: correction, it will move with the treadmill untill the movement causes enough air to move over the wings to provide the lift. then it will bounce. up as the plane gets lifted, then down when the air stops moving then up... but still backwards as there would be no force to counter the friction of the runway.

Why won't the plane, with no other force acting upon it, simply move with the treadmill? Why would the wheels begin spinning at all?

the wheels on the plane are sitting on the treadmill. as the treadmill moves under it, it would cause the wheels to spin. The wheels aren't really attached to the plane drive shaft (IE there isn't one) so as the treadmill moves under the plane, the wheels spin, but the plane doesn't go anywhere.

Why won't the plane, with no other force acting upon it, simply move with the treadmill? Why would the wheels begin spinning at all?

Because this a free body model, so we're ignoring the affects of friction. In order for the treadmill to apply force to the plane, there has to be some friction in the wheel assembly. If there is no friction, the wheels will spin freely, transferring none of the energy of the moving treadmill to the plane.

because weight will still be on the wheels and that would help provide the friction to keep the plane on the treadmill.

Well yes, but we're ignoring friction this example.



try this. take a toy car with a piece of string attached (your plane) and put it on one end of a treadmill at any gym. Give it a gentle but steady pull (your pulling is the props of the plane pulling the car forward) and pull the car to the other end of the treadmill. When your car reaches the halfway point of the treadmill, have someone turn it on. Will your car become stationary or continue to move forward? would you need to pull harder or not?

That won't work. Turning the treadmill on will cause the treadmill to accelerate rapidly to its speed, this will cause an initial "pushback" on the car. You have to drop the car on an already moving treadmill.

I'm still not sure what Wilgrove was taught, or what he thinks the left/right/both part of the checklist is testing.

I cannot even form a response. How freely the key moves??? Maybe he's one of the pilots that thinks checklists are optional?

Reminds me of a pilot who crashed a 182 because he didn't put carb heat on for landing. A checklist item!!!!!! And it was a conscious choice on his part. He stated there were "two schools of thought" on the matter. No there's not!

Edit: Then again, it would have only been a dead stick landing if the idiot could set up a proper approach.


I certainly hope he never has his alternator belt break on him in flight.:P

the wheels on the plane are sitting on the treadmill. as the treadmill moves under it, it would cause the wheels to spin. The wheels aren't really attached to the plane drive shaft (IE there isn't one) so as the treadmill moves under the plane, the wheels spin, but the plane doesn't go anywhere.
I'm sorry, but that seems wrong to my fairly-well-developed intuition of physics. There is no force to keep the plane from moving backwards with the treadmill. The wheels will not start to spin. No point arguing it, tho, if you cannot be convinced of this.

Because this a free body model, so we're ignoring the affects of friction. In order for the treadmill to apply force to the plane, there has to be some friction in the wheel assembly. If there is no friction, the wheels will spin freely, transferring none of the energy of the moving treadmill to the plane.
Err. "free body model"? The OP isn't talking about the real world? If we can selectively ignore inconvenient real world forces, then I say no motion at all is possible, per Zeno's Paradox, so the plane still can't take off. So there!

Well yes, but we're ignoring friction this example. well, technically, if you ignore friction then a car won't move since a car relies on friction between the wheel and the ground. :p

That won't work. Turning the treadmill on will cause the treadmill to accelerate rapidly to its speed, this will cause an initial "pushback" on the car. You have to drop the car on an already moving treadmill. yes it will. because as the treadmill accelerates, the wheels would spin relative to the treadmill. like a plane recieving it's thrust from the props/turbine/jet, the string is providing the thrust and the wheels are free spining.

now holding onto the car and pushing it might provide the small pushback, but that would be because you're putting your weight/pressure down onto the treadmill. same if you 'drop' the car onto a moving treadmill. the initial contact and brief application of weight will provide more of a pushback than accerating the treadmill.

I'm sorry, but that seems wrong to my fairly-well-developed intuition of physics. There is no force to keep the plane from moving backwards with the treadmill. The wheels will not start to spin. No point arguing it, tho, if you cannot be convinced of this.
You're right. The plane is not going to stand still without a force preventing it from not moving backward. To assert otherwise is ridiculous. In a frictionless environment that might be true, but even then it still sounds slightly dubious because wouldn't some friction be needed to spin the wheels? The friction provided by the treadmill on the wheels would have to be some notable amount greater than the friction between the wheel and its attachment to the plane which doesn't strike me as very likely..

Wouldn't the wind have to be constantly accelerating to match the engine's thrust?

First, I should express it correctly as an opposing vector. The answer is, not in my example. I was assuming steady state conditions. I abandoned the treadmill as was trying to get back to normal flight mechanics.

Err. "free body model"? The OP isn't talking about the real world? If we can selectively ignore inconvenient real world forces, then I say no motion at all is possible, per Zeno's Paradox, so the plane still can't take off. So there!

If one adds friction, the plane still takes off.
Let us rewrite the problem a bit.

- Say that a plane is able to take off when it has achieved a forward speed v.
- This plane is placed on a long conveyor belt that is moving in the opposite direction of the planes nose at a speed of 2v (or -2v if you prefer).
- Result: the plane will start to move backward with the conveyor belt at a speed 2v, due to friction, the plane being heavy and so on.
- The plane now starts its engines. A forward force is applied. Pretty soon it is powerful enough to defeat the initial friction.
- Under the force of the engines, the plane starts to move forward. The conveyor belt no longer effects its motion - it just makes the wheels spin.
- The plane accelerates and takes off normally.

Voila.

Err. "free body model"? The OP isn't talking about the real world? If we can selectively ignore inconvenient real world forces, then I say no motion at all is possible, per Zeno's Paradox, so the plane still can't take off. So there!

In any case, all the plane has to do is be able to compensate for the increaesed friction of the wheels spinning twice as fast (which will be fairly small). In a real world case, the treadmill would be a hindrance, but not a barrier.

If one adds friction, the plane still takes off.
Let us rewrite the problem a bit.

- Say that a plane is able to take off when it has achieved a forward speed v.
- This plane is placed on a long conveyor belt that is moving in the opposite direction of the planes nose at a speed of 2v (or -2v if you prefer).
- Result: the plane will start to move backward with the conveyor belt at a speed 2v, due to friction, the plane being heavy and so on.
- The plane now starts its engines. A forward force is applied. Pretty soon it is powerful enough to defeat the initial friction.
- Under the force of the engines, the plane starts to move forward. The conveyor belt no longer effects its motion - it just makes the wheels spin.
- The plane accelerates and takes off normally.

Voila.
In any case, all the plane has to do is be able to compensate for the increaesed friction of the wheels spinning twice as fast (which will be fairly small). In a real world case, the treadmill would be a hindrance, but not a barrier.
Okay! I now perceive my confusion. I took the OP to imply that the airplane was merely overoming the action of the treadmill, and therefore remaining stationary with respect to the rest of Earth. Given a long enough treadmill, I suppose you could then proceed down it like a runway and take off, but it would be a tremendous waste. My assumption was that implicit to the OP was an idea to create a VTOL capacity for non-VTOL craft, which would save quite a bit of real estate, except it won't work.

No, it would just move over the threadmill as if the threadmill was standing still.

Or lift straight up if it is a harrier ;)

at what point would it start moving forward? would it go from an actual land speed of zero to ....well whatever takeoff speed is...in an instant?


of course the real answer is that the airplane fairies dont like treadmills and would have nothing to do with any airplane travelling on one so they would never grab it and take it off into the air.

Hmmm... when it's night in the US the No option is gaining, and when it's day in the US the Yes option is gaining. Stereotypes at work, huh?

I finally understand now. After it kept popping into my head the last couple of days and I'd think about it. No matter how fast the treadmill goes .. if the plane is thrusting forward it will go forward. Basically the treadmill doesn't even matter. It would move forward on the treadmill as it would on the ground. The thrust is what matters .. not what the wheels or those water landing things are touching .. treadmill .. water rushing in opposite direction etc .. because it puts no additional opposing force onto the plane.

I'm probably not describing it right .. but I understand why it can now, and why the ground moving in the opposite direction doesn't matter.. and .. well that's all that matters.

Now I'm wondering about something else. Is there anything different going on with the wheels during all of this. I mean would the wheels cover more feet or spin faster when the plane thrusts forward? I'm thinking no. But not sure.

Hmmm... when it's night in the US the No option is gaining, and when it's day in the US the Yes option is gaining. Stereotypes at work, huh?

That Americans understand physics better than the rest of the world?

That Americans understand physics better than the rest of the world?Exactly the opposite.

Exactly the opposite.

So Yanks getting the answer right during their day means they don't get physics?

Exactly the opposite.

Considering the plane actually *can* take off... I fear not.

*makes his little remote controlled airplane lift of from the conveyor belt a few more times - just because he can*

That Americans understand physics better than the rest of the world?
nah, UB thinks that people only post during the night.

Now I'm wondering about something else. Is there anything different going on with the wheels during all of this. I mean would the wheels cover more feet or spin faster when the plane thrusts forward? I'm thinking no. But not sure.

They would spin faster (or burn up). Everything else in your post is quite right :)

You're right. The plane is not going to stand still without a force preventing it from not moving backward. To assert otherwise is ridiculous.What the fuck? Quadruple negative! x_x

I think I can cut it down to -
The plane is going to stand still with a force moving it backward.

Asserting otherwise perhaps isn't so ridiculous. If this isn't what you meant then try using more positive phrasing.

Not on that which was not a mat did not the cat not sit. Understand what I'm attempting to say?

In a frictionless environment that might be true, but even then it still sounds slightly dubious because wouldn't some friction be needed to spin the wheels? The friction provided by the treadmill on the wheels would have to be some notable amount greater than the friction between the wheel and its attachment to the plane which doesn't strike me as very likely..Huh? I'm pretty sure this is the case. That there is plenty of friction between the wheel and the ground, but not between the wheel and the plane. Otherwise the wheel wouldn't work.

I think I can cut it down to -
The plane is going to stand still with a force moving it backward.
No, the plane isn't going to stand still with a treadmill moving backwards unless there is a force acting on it to stop it.

Huh? I'm pretty sure this is the case. That there is plenty of friction between the wheel and the ground, but not between the wheel and the plane. Otherwise the wheel wouldn't work.
What I mean is why would there be friction between the ground and the wheel surface but not the wheel and the plane? Of course there is going to be less between the wheel and the plane, but enough that the plane stays at a stand still when a treadmill starts?

No, the plane isn't going to stand still with a treadmill moving backwards unless there is a force acting on it to stop it.


What I mean is why would there be friction between the ground and the wheel surface but not the wheel and the plane? Of course there is going to be less between the wheel and the plane, but enough that the plane stays at a stand still when a treadmill starts?The way I see it there are three scenarios.

a) the sudden force when the treadmill starts is greater than the friction between both the ground and the wheel, and between the plane and the wheel. In this case the plane does not initially move, but begins to move once the only remaining force is friction.
b) the sudden force is not greater than the friction between the ground and the wheel, or between the plane and the wheel. In this case the plane will move.
c) the sudden force is only greater than the friction between the wheel and the plane. This will cause the plane to tip forwards and begin to move backwards.

Reminds me of a pilot who crashed a 182 because he didn't put carb heat on for landing. A checklist item!!!!!! And it was a conscious choice on his part. He stated there were "two schools of thought" on the matter. No there's not!

Obviously, fuel-injected aircraft don't have carburetors. They don't need carb heat, either. Maybe he was confused? But when in doubt, read the checklist. That's why they have it placarded on the instrument panel.

No, the plane isn't going to stand still with a treadmill moving backwards unless there is a force acting on it to stop it.

Why the hell would it move backwards? What force is working on the plane to move it backwards?

Force on the tires certainly, but that force is put into the tires and causing them to spin. There's nothing stopping the tires from spinning, so the force exerted on the tires will simply cause them to spin around, that force won't be applied to the plane

Why the hell would it move backwards? What force is working on the plane to move it backwards?

Force on the tires certainly, but that force is put into the tires and causing them to spin. There's nothing stopping the tires from spinning, so the force exerted on the tires will simply cause them to spin around, that force won't be applied to the plane
err... but with no counterforce (like thrust from the engines) the force on the tires will still move the whole plane backwards.

Obviously, fuel-injected aircraft don't have carburetors. They don't need carb heat, either. Maybe he was confused? But when in doubt, read the checklist. That's why they have it placarded on the instrument panel.
He knew full well it was a checklist item, he just disagreed in the logic behind it.

err... but with no counterforce (like thrust from the engines) the force on the tires will still move the whole plane backwards.

No, it would not. Why would it? The The tires are not locked in place, they turn freely The force on the tires will cause the tires to turn, nothing more. The treadmill applies force to the tires. The force on the tires, which are free to turn, and not locked in place, will cause the tires to spin around as the force is applied ot it by the treadmill. Force on the tires is not transfered to the rest of the plane. Why would it? The tires can turn freely.

No, it would not. Why would it? The The tires are not locked in place, they turn freely The force on the tires will cause the tires to turn, nothing more. The treadmill applies force to the tires. The force on the tires, which are free to turn, and not locked in place, will cause the tires to spin around as the force is applied ot it by the treadmill. Force on the tires is not transfered to the rest of the plane. Why would it? The tires can turn freely.

In an ideal situation with 0 friction yes... you would have no energy transfered to the plane in which to overcome its momentum

In the real world it would move some

No, it would not. Why would it? The The tires are not locked in place, they turn freely The force on the tires will cause the tires to turn, nothing more. The treadmill applies force to the tires. The force on the tires, which are free to turn, and not locked in place, will cause the tires to spin around as the force is applied ot it by the treadmill. Force on the tires is not transfered to the rest of the plane. Why would it? The tires can turn freely.Consider a plane at rest on the Earth, and the Earth as one giant treadmill. Why are its wheels not turning freely when the Earth is spinning below it.

Snip

Huh? I'm pretty sure this is the case. That there is plenty of friction between the wheel and the ground, but not between the wheel and the plane. Otherwise the wheel wouldn't work.

Yes it would even ball bearings/sleeve bearings have SOME friction ... but again even less then the tire against the ground

In the end there always is SOME friction ... it is just a low amount

Consider a plane at rest on the Earth, and the Earth as one giant treadmill. Why are its wheels not turning freely when the Earth is spinning below it.

Because there is no horizontal force acting on it as it is traveling the same speed as the earth. Now if the earth were to accelerate or change velocity they might spin same if the speed is at rest relative to the treadmill rather then the earth.

No, it would not. Why would it? The The tires are not locked in place, they turn freely The force on the tires will cause the tires to turn, nothing more. The treadmill applies force to the tires. The force on the tires, which are free to turn, and not locked in place, will cause the tires to spin around as the force is applied ot it by the treadmill. Force on the tires is not transfered to the rest of the plane. Why would it? The tires can turn freely.
the weight of the plane (remember, engine is off) will push down on the tires since the plane won't have lift (dropping the plane onto the treadmill) adding pressure that, without any counterforce, will have the plane moving with the treadmill.

Think of an aircraft carrier. they have planes with their engine's off on deck and you don't see them remaining motionless while the ship moves out from under them. :p

Remember, we are talking plane with engine off being dropped onto a treadmill (even if it was gently lowered, the moment the weight is taken up totally by the landing gears, it will move in the direction of the treadmill.)

the quote that started it.
The wheels on a plane are not connected to a drive shaft like they are on a car. If you take a plane, with the engine OFF, and drop it on a treadmill, it won't go anywhere. The treadmill will move under the wheels, and the wheels will just...spin. The wheels aren't connected to any drive shaft, them spinning won't move the plane. The treadmill will just cause the wheels of the plane to spin, but the plane, with it's engine off, won't move.

When the plane turns its engine on and begins moving forward, again, the treadmill will do nothing. A plane is not driven by its wheels, it is driven by its turbine. The wheels merely serve to reduce friction with the ground.

by your same assertion, a ball (a wheel that is NOT attached to anything, much less the landing gear of a plane) dropped (or placed) on a treadmill should also remain motionless, but it won't. heck, try it with skates, or a skateboard. the same thing will happen.

In fact there's a fairly easy test. Get a piece of paper, a pencil and a flat surface. Drag the paper across the surface, at a stead pace. As it is moving, drop the pen on it. Does the pen move with the paper, or stay in place and just spin as the paper moves under it?tried this. no matter what surface I used, the pen moved with the paper. the only difference was when I did it on an incline, then the pen rolled down the incline dispite the direcion of the paper.

You can't start with the pen on the paper then suddenly move it, as that is a matter of acceleration not speed, and we're just talking about basically dropping a plane on a moving treadmill. and if you try this with a gradual moving of the paper? Lo the pen moves with the paper! so it's NOT about acceleration, but the degree of the transfer of energy.

EDIT: actually, the pen does move with the paper, even while it's spinning.

Without equivalent forward momentum (i.e., the engine delivering as much net thrust as, or greater than, the treadmill) the aircraft would go backwards. Besides, you would need an awful large treadmill requiring a hell of a lot more energy than any aircraft would require to take off (energy required to move the treadmill + energy to move aircraft mass = waste of energy).

EDIT: I was wrong -- Damn you, NS General!

imagine a normal treadmil with its side arias for safetythen put a skatebord(represents plane)on the rolling part stand on it as it rolls then push forwod with your feet (represents thrust)on the non moving side what happens?...
the bourd moves forward at a slightly slower speed than normaly
but not to slow if youi go back to the plane the ratios are just about the same so the crew may have to turn the engine up abit to counter allthe resistance

Yes it would even ball bearings/sleeve bearings have SOME friction ... but again even less then the tire against the ground

In the end there always is SOME friction ... it is just a low amountI didn't mean to imply there was no friction. I must have phrased that badly.

Because there is no horizontal force acting on it as it is traveling the same speed as the earth.A poor example perhaps then. I was trying to show that the plane would move if Force<=Friction (ground/wheel).

If Force>Friction then the wheels will turn, but the plane will begin to move once Force<=Friction (the treadmill will not go on accelerating forever, and at some point Force will equal 0 and Friction will stop the wheels spinning and start the plane moving).

Now if the earth were to accelerate or change velocity they might spin same if the speed is at rest relative to the treadmill rather then the earth.I don't understand this sentence. The phrasing is odd...

actualy the bearings in the wheels may give out due to the exdra stress of moving twice as fast or the tires might overheat and explode theres so many different things to go rong with the landing gear

No.

You need air to go over the wings of a plane to take off. If a plane is on a treadmill, then it will move because the prop or jet will create thrust. But the plane cannot take off unless air flows over the wings. If you pointed a giant high speed fan at the airplane, then it could take off. But you have to remember that the airplane is not moving forward relative to the earth or atmosphere, so as soon as the plane leaves the treadmill and the wind of the fan, it will drop like a stone.

This is the correct answer.

I didn't mean to imply there was no friction. I must have phrased that badly.

A poor example perhaps then. I was trying to show that the plane would move if Force<=Friction (ground/wheel).

If Force>Friction then the wheels will turn, but the plane will begin to move once Force<=Friction (the treadmill will not go on accelerating forever, and at some point Force will equal 0 and Friction will stop the wheels spinning and start the plane moving).

I don't understand this sentence. The phrasing is odd...

Sorry meant might spin SOME not same lol and yeah you are right

This is the correct answer.

Nope

No Child Left Behind at work.

Nope

Those poll results are scary.

This is the correct answer.


That's the whole thing .. and what I didn't understand at first ..

The plane, no matter it being on a treadmill, WILL move forward 'relative to the earth' or whatever the same as it would on the ground. It would not just be spinning its wheels and not moving forward. It took me a bit to understand it too.

And Wilgrove (I think it was him -- if not sorry) had a good idea.. We should write in to Mythbusters .. they could sure do it...and I'd like to see it.

I just created a login name at Discovery .. and will search to see if anyone has posted this yet. If not I will create a thread for it in the

Show Ideas: From Here to There...Transport Myths
Gas mileage, car capers, air plane myths - anything that has to do with transportation, post here.

section.

http://community.discovery.com/eve/forums/a/cfrm/f/2991937776

edit.. there's a few (http://community.discovery.com/eve/forums?use_forum_scope=on&a=search&reqWords=treadmill&s=6941912904&forum_scope=9551919888) of them already there..

Those poll results are scary.

I agree ... they are every time

That's the whole thing .. and what I didn't understand at first ..

The plane, no matter it being on a treadmill, WILL move forward 'relative to the earth' or whatever the same as it would on the ground. It would not just be spinning its wheels and not moving forward. It took me a bit to understand it too.

And Wilgrove (I think it was him -- if not sorry) had a good idea.. We should write in to Mythbusters .. they could sure do it...and I'd like to see it.

I just created a login name at Discovery .. and will search to see if anyone has posted this yet. If not I will create a thread for it in the

Show Ideas: From Here to There...Transport Myths
Gas mileage, car capers, air plane myths - anything that has to do with transportation, post here.

section.

http://community.discovery.com/eve/forums/a/cfrm/f/2991937776

edit.. there's a few (http://community.discovery.com/eve/forums?use_forum_scope=on&a=search&reqWords=treadmill&s=6941912904&forum_scope=9551919888) of them already there..

It appears they are scheduled to show it 2/12/2007.

And Wilgrove (I think it was him -- if not sorry) had a good idea.. We should write in to Mythbusters .. they could sure do it...and I'd like to see it.

I just created a login name at Discovery .. and will search to see if anyone has posted this yet. If not I will create a thread for it in the

Show Ideas: From Here to There...Transport Myths
Gas mileage, car capers, air plane myths - anything that has to do with transportation, post here.

section.

http://community.discovery.com/eve/forums/a/cfrm/f/2991937776

edit.. there's a few (http://community.discovery.com/eve/forums?use_forum_scope=on&a=search&reqWords=treadmill&s=6941912904&forum_scope=9551919888) of them already there..

Watch for yourself. The Mythbusters are scheduled to bust this myth on 12/12/2007.

So... I need to ask someone to tape this...

It appears they are scheduled to show it 2/12/2007.

Sweet! Let's all watch it .. together. :p

12/12/07

Yea but what if it's a prop aircraft, wouldn't the wind from the prop give some winds for lift?

The props would not give anything like sufficient airflow for lift. The plane is going nowhere, we all know that a plane's wings are its means of flight, in particular the negative pressure created when air flows over its wings. If there is not sufficient airflow, the plane will not take off. As simple as that.

Sweet! Let's all watch it .. together. :p

12/12/07

Yeah missed the 1 in the copy and paste lol

The props would not give anything like sufficient airflow for lift. The plane is going nowhere, we all know that a plane's wings are its means of flight, in particular the negative pressure created when air flows over its wings. If there is not sufficient airflow, the plane will not take off. As simple as that.

From that anyways ... but as it accelerates and gains sufficient lift it will fly.

the plane can take off. just cuz the treadmill is going at the planes takeoff velocity doesn't mean that the plane can't take off. the wheels aren't attatched to the mill, so the plane can generate a force enough to take off without problems. enough said. next topic.

the plane can take off. just cuz the treadmill is going at the planes takeoff velocity doesn't mean that the plane can't take off. the wheels aren't attatched to the wheels, so the plane can generate a force enough to take off without problems. enough said. next topic. :confused:

(as for the other parts, not everyone get's it yet... :p )

This poll depresses the hell out of me. Airplanes are not cars damn it! It doesn't matter if the treadmill under it is moving at the speed of light in a practical model, the plane will still take off. The wheels will roll, but the plane won't move backwards because of Newton's laws of motion!Fixed.

I like to think that it's the Kutta condition at the sharp trailing edge that really makes lift possible... But Bernoulli is an okay introduction.I like to think that the Flying Spagetti Monster hires a bunch of invisible gnomes to lift the plane off the ground. They stand one on top of each other until they reach the desired height, then the bottom one runs really fast, for if the planes wheels are not touching the ground how does it propel itself forward.

So yes, the plane will take off, but it won't go anywhere as the gnome won't be able to get off the treadmill.

I say no. Why? Because I am a pessimist today. :)

I like to think that the Flying Spagetti Monster hires a bunch of invisible gnomes to lift the plane off the ground. They stand one on top of each other until they reach the desired height, then the bottom one runs really fast, for if the planes wheels are not touching the ground how does it propel itself forward.

So yes, the plane will take off, but it won't go anywhere as the gnome won't be able to get off the treadmill.

nu uh

its the plane fairies.

but geez how about everyone tries the simple thought experiment of "should the plane get lift, where would it go?"

wouldnt it have to go straight up in the air? and since is has NO forward momentum relative to the earth except in the wheels that are no longer connected to the ground. wont it then just crash downwards?

if it could get lift, which it obviously cant.

I'm going to go with an obvious answer here. My answer has nothing to do with physics because the friction caused by the movement of the wheels is not sufficient to provide thrust and/or lift so the idea fails on that level. My economic theory is that there's no way in hell it could work or the airline industry would have used the concept and saved time, space, and millions of dollars on creating terminals, runways, etc. Further, if this concept were to be taken to it's logical conclusion this would mean planes could land on a treadmill traveling in reverse without having to use any more space then the airplane itself would take up. Either way the idea is nonsense. Any flyboys here want to explain minimum speed requirements for take offs and landing from both land based and carrier based systems? Our boys like to come in by sea mostly.

The plane could take of because if you gained enough speed the plane would taxi off the treadmill and given enough room would eventually take off as planes are designed to do, or it could crash when it reaches the end of the runway due to the sudden shock of speed when the wheels leave the treadmill. Planes will always find a way! LOL

What the fuck? Quadruple negative! x_x

I think I can cut it down to -
The plane is going to stand still with a force moving it backward.

Asserting otherwise perhaps isn't so ridiculous. If this isn't what you meant then try using more positive phrasing.

Not on that which was not a mat did not the cat not sit. Understand what I'm attempting to say?

Huh? I'm pretty sure this is the case. That there is plenty of friction between the wheel and the ground, but not between the wheel and the plane. Otherwise the wheel wouldn't work.The treadmill is going to apply a force on the wheel (for the sake of creativity I shall call it F). This force acts on the wheel at its bottom. The wheel's center of mass is not at its bottom, but near the center, which is a distance d from the bottom of the wheel. So there is a torque, T, of magnitude Fd. T causes the wheel to increase in angular momentum or spin if you will. However, this does not make the F go away. It is still acting on the wheel, and it will accelerate the wheel backwards at a rate equal to F/m, where m is the wheel's mass. So the wheel is accelerating backwards, and it collides with the axle poking through it which is rigidly attached to the plane. Conservation of momentum comes into effect and the plane gets receives an impulse from the wheel which increases the planes momentum, backwards. The wheel bumps the axle several times until the two eventually stick together, and are accelerated backwards \ by the force F.

nu uh

its the plane fairies.

but geez how about everyone tries the simple thought experiment of "should the plane get lift, where would it go?"

wouldnt it have to go straight up in the air? and since is has NO forward momentum relative to the earth except in the wheels that are no longer connected to the ground. wont it then just crash downwards?

if it could get lift, which it obviously cant.The last 300 posts (the last 100 post have been some irrelevant side discussion that everyone thinks is relevant, but w/e) the people saying it will take off have been trying to show that the plane will be moving relative to the Earth. The general argument from that side is that rolling friction is independent of the speed the wheel rotates. Compared to a normal takeoff, the only difference will be the speed at which the wheels on the plane rotate. If the plane is traveling at 50m/s (with respect to the Earth), it will still be moving at 50m/s relative to the Earth on the treadmill. It may be moving at 100m/s relative to the treadmill, but that makes no difference in the friction. The plane will take off in its normal curvy motion once it leaves the ground.

I'm going to go with an obvious answer here. My answer has nothing to do with physics because the friction caused by the movement of the wheels is not sufficient to provide thrust and/or lift so the idea fails on that level. My economic theory is that there's no way in hell it could work or the airline industry would have used the concept and saved time, space, and millions of dollars on creating terminals, runways, etc. Further, if this concept were to be taken to it's logical conclusion this would mean planes could land on a treadmill traveling in reverse without having to use any more space then the airplane itself would take up. Either way the idea is nonsense. Any flyboys here want to explain minimum speed requirements for take offs and landing from both land based and carrier based systems? Our boys like to come in by sea mostly.

Wait what? how would this SAVE space? The plane would take roughly the same amount of distance relative to the earth as if there was no treadmill

Your economic theory would be sound if the idea actually saved money or space but it does not it just adds needless and irrelevant complexity to a simple idea.

Umm... while I'm used to working in situations that ignore silly things like friction and air resistance, I'm pretty sure that planes fly because the air on top of the wings is moving at a higher speed and thus at a lower pressure than the air underneath. Now, if the treadmill is going at the same speed backwards as the plane is moving forwards, the plane's velocity and the treadmill's velocity will cancel and the plane won't go anywhere, thus, the plane won't get any lift, thus will remain on the ground.

Umm... while I'm used to working in situations that ignore silly things like friction and air resistance, I'm pretty sure that planes fly because the air on top of the wings is moving at a higher speed and thus at a lower pressure than the air underneath. Now, if the treadmill is going at the same speed backwards as the plane is moving forwards, the plane's velocity and the treadmill's velocity will cancel and the plane won't go anywhere, thus, the plane won't get any lift, thus will remain on the ground.

Why? the plane is thrusting against the air not the treadmill and the wheels are free spinning

Simple test for yourself think of what would happen take a toy car or airplane ... think of you holding it in place with your finger as the treadmill spins ... do you think you can press the car forward reguardless of the speed of the treadmill?

If the answer is yes then you know why the plane can take off as it WILL gain forward speed

In the end the treadmill has NOTHING to do with the problem in an ideal situation as the thrust is produced by pushing against the air not the treadmill (just like your finger in the example)

Why? the plane is thrusting against the air not the treadmill and the wheels are free spinning
The wheels experience friction with the ground, they're not freely spinning.

Simple test for yourself think of what would happen take a toy car or airplane ... think of you holding it in place with your finger as the treadmill spins ... do you think you can press the car forward reguardless of the speed of the treadmill?
These are poor models, the frictional force is proportional to the normal force which is equal and opposite to the force of gravity acting on an object. This means that the wheels of a heavy jumbo jet will experience much more friction than the wheels of a toy plane.

However, if we're talking about making the airplane go much faster than it normally would on the ground to takeoff and the conveyor belt does not match this speed in the reverse direction, then it would be possible. However, it's definitely not possible at normal takeoff velocity.

These poll results are making me sad. :(


All this talk of rolling friction and angular momentum is pretty irrelevant since even if they are calculated in the most generous manner possible, they are insignificant compared to the thrusting power of the airplane.

All this talk of rolling friction and angular momentum is pretty irrelevant since even if they are calculated in the most generous manner possible, they are insignificant compared to the thrusting power of the airplane.
Oh take off, would you? Not everyone considers the plane going much faster than its normal takeoff velocity as part of the question. You don't need to be a jerk about it.

The wheels experience friction with the ground, they're not freely spinning.


These are poor models, the frictional force is proportional to the normal force which is equal and opposite to the force of gravity acting on an object. This means that the wheels of a heavy jumbo jet will experience much more friction than the wheels of a toy plane.

However, if we're talking about making the airplane go much faster than it normally would on the ground to takeoff and the conveyor belt does not match this speed in the reverse direction, then it would be possible. However, it's definitely not possible at normal takeoff velocity.

The wheels on the airplane will spin at twice the ordinary take-off rate, but the plane will move forward relative to a fixed point on the ground and the air at ordinary takeoff velocity.

The turning of the wheels on a plane doesn't cause it to move faster or slower, because it is not propelled by its wheels.

The fundamental first-principle function of the wheels on a plane is opposite from those on a car. On a car, the wheels function to maximize friction between the car and the ground, on a plane they function to minimize it.

There are more detailed explanations back in the thread. Recant before you dig a deeper hole!

Oh take off, would you? Not everyone considers the plane going much faster than its normal takeoff velocity as part of the question. You don't need to be a jerk about it.


The plane doesn't need to go faster than its normal takeoff velocity. That's the whole point. The treadmill does almost nothing to slow down the plane because the plane's wheel are free rolling. It may as well be on iceskates and the treadmill be made of ice.

I wasn't being a jerk. No need to be a bitch about it.

The wheels experience friction with the ground, they're not freely spinning.

True but would that friction be enough to impede takeoff?

Add to that, the fact that in most cases with a physics theoretical like this we deal in an idolized world with lack of friction

But in the end I guess the question is do certain planes have enough thrust to overcome this friction.


These are poor models, the frictional force is proportional to the normal force which is equal and opposite to the force of gravity acting on an object. This means that the wheels of a heavy jumbo jet will experience much more friction than the wheels of a toy plane.


True ... Though the plane I suppose will have more thrust as well

However, if we're talking about making the airplane go much faster than it normally would on the ground to takeoff and the conveyor belt does not match this speed in the reverse direction, then it would be possible. However, it's definitely not possible at normal takeoff velocity.

Why would the velocity of takeoff be changed?

I can see the thrust being required to accelerate the plane to takeoff speed being different but the velocity relative to the earth/air should be the same

And what does the conveyor belt have anything to do with anything other then friction? if so why would it matter if the speed is matched?

The wheels on the airplane will spin at twice the ordinary take-off rate, but the plane will move forward relative to a fixed point on the ground and the air at ordinary takeoff velocity.
No it won't. There is a force of friction between the wheels on the airplane and the ground. If there wasn't, then a toddler could push the plane down the runway. Hell, if there wasn't any friction between the wheels of the plane and the ground then the plane would never go anywhere to begin with.

The turning of the wheels on a plane doesn't cause it to move faster or slower, because it is not propelled by its wheels.
No shit it's not propelled by its wheels, its wheels don't have little engines. That doesn't mean that the wheels aren't attached to the plane and touching the ground. It also doesn't mean that the wheels do not experience a frictional force with respect to the ground.

The fundamental first-principle function of the wheels on a plane is opposite from those on a car. On a car, the wheels function to maximize friction between the car and the ground, on a plane they function to minimize it.
I don't think they wheels on a plane are functioning to minimize friction with respect to the ground. You want friction with the ground when the plane is trying to take off, this allows it to accelerate.

There are more detailed explanations back in the thread. Recant before you dig a deeper hole!
Umm... no.

The wheels experience friction with the ground, they're not freely spinning.


These are poor models, the frictional force is proportional to the normal force which is equal and opposite to the force of gravity acting on an object. This means that the wheels of a heavy jumbo jet will experience much more friction than the wheels of a toy plane.

However, if we're talking about making the airplane go much faster than it normally would on the ground to takeoff and the conveyor belt does not match this speed in the reverse direction, then it would be possible. However, it's definitely not possible at normal takeoff velocity.So, the effect a force has is inversely proportional to the objects mass, which is proportional to its normal force under normal circumstances. So while the jet may experience a force of friction 1000 times larger than the toy, it will also be 1000 times more resistant to the force.

The plane doesn't need to go faster than its normal takeoff velocity. That's the whole point. The treadmill does almost nothing to slow down the plane because the plane's wheel are free rolling. It may as well be on iceskates and the treadmill be made of ice.
The wheels aren't free rolling, they experience friction. A large amount of friction if you're talking about a large aircraft. And the plane doesn't need to go faster relative to a fixed object on the ground, but its thrusters need to work harder to get it to the correct velocity because it needs to accelerate longer to get to the correct velocity relative to the backwards moving ground.

I wasn't being a jerk. No need to be a bitch about it.
Yes, you were being a jerk.

Snip


I don't think they wheels on a plane are functioning to minimize friction with respect to the ground. You want friction with the ground when the plane is trying to take off, this allows it to accelerate.


Umm... no.

Wait? Then how does a plane accelerate in the air if the friction with the ground is what allows it to accelerate?

No it won't. There is a force of friction between the wheels on the airplane and the ground. If there wasn't, then a toddler could push the plane down the runway. Hell, if there wasn't any friction between the wheels of the plane and the ground then the plane would never go anywhere to begin with.


No shit it's not propelled by its wheels, its wheels don't have little engines. That doesn't mean that the wheels aren't attached to the plane and touching the ground. It also doesn't mean that the wheels do not experience a frictional force with respect to the ground.


I don't think they wheels on a plane are functioning to minimize friction with respect to the ground. You want friction with the ground when the plane is trying to take off, this allows it to accelerate.


Umm... no.

The toddler can't push the plane because of inertia, not friction.

You say that "You want friction with the ground when the plane is trying to take off, this allows it to accelerate. "

This would be true only if the plane were propelled by its wheels - which you agree is not the case.


I say this as non-jerkily as possible.

The wheels aren't free rolling, they experience friction. A large amount of friction if you're talking about a large aircraft. And the plane doesn't need to go faster relative to a fixed object on the ground, but its thrusters need to work harder to get it to the correct velocity because it needs to accelerate longer to get to the correct velocity relative to the backwards moving ground.


Yes, you were being a jerk.

True providing the same forward force ... an increased backwards force (due to friction) the acceleration period will be longer in time but not necessarily in velocity which was the original statement both me and him argued

Its fine! just trying to get things cleared up

True but would that friction be enough to impede takeoff?
At normal thruster speed, yes.

Add to that, the fact that in most cases with a physics theoretical like this we deal in an idolized world with lack of friction
We're not talking about a theoretical model though, we're asking if a real life air plane will take off.

But in the end I guess the question is do certain planes have enough thrust to overcome this friction.
They probably do, but they would need more thrust than in a normal situation where the ground is not moving.

Why would the velocity of takeoff be changed?
The takeoff velocity relative to the backwards moving ground would be doubled. Relative to the plane (and the rest of the world) it wouldn't, but the thrusters would need to work harder. I might have phrased that poorly.

At first I didn't consider the system where the plane is going faster than its normal takeoff speed.

The toddler can't push the plane because of inertia, not friction.

You say that "You want friction with the ground when the plane is trying to take off, this allows it to accelerate. "

This would be true only if the plane were propelled by its wheels - which you agree is not the case.


I say this as non-jerkily as possible.

Well to be fair the ball bearing and material friction is probably enough to overcome the effects of a toddler ... the wheel is not COMPLEATLY free spinning though that is what it is working towards.

because it needs to accelerate longer to get to the correct velocity relative to the backwards moving ground.




It's velocity relative the ground is meaningless. Only it's velocity to the air around the plane is meaningful. The treadmill does virtually nothing to slow the plane in relation to the air or a fixed point on the ground.

At normal thruster speed, yes.


but at a percent or two higher it would be able to?

Then yeah maybe but I don't know of a plane that runs so close to the max that it would not be able to adjust that much

And military jets have multiplies of the power that are needed for takeoff on a reasonable length runway.

We're not talking about a theoretical model though, we're asking if a real life air plane will take off.


They probably do, but they would need more thrust than in a normal situation where the ground is not moving.

I agree with you here no problem it probably would need to overcome some more friction so it COULD take off, at least any airplane I know of.

The takeoff velocity relative to the backwards moving ground would be doubled. Relative to the plane (and the rest of the world) it wouldn't, but the thrusters would need to work harder. I might have phrased that poorly.

At first I didn't consider the system where the plane is going faster than its normal takeoff speed.

Then absolutely with the clear up I agree!

The toddler can't push the plane because of inertia, not friction.
Uh.... seriously?
What level of physics have you attained?

Ok, so you have a force of static friction which is described by F_f=u_s*F_N (pretend the u is a mu, I can't do greek letters here). F_N is exactly equal and opposite to F_g, the force of gravity on the airplane (which can be approximated to be described as F_g=mg, where m is the mass of the airplane and g is ~ -9.8m/s^2). Now let's say that the airplane's mass is on the order of 10,000 kg and u_s is on the order of 1, the child would need to generate 10,000N of force to move the airplane, which a child with a mass on the order of ~10kg would not be able to do.

If you want, we can do a simpler system which removes your intertia argument altogether. Let's say we have a plane in motion (very slow motion) and we turn off its thrusters or remove the taxi or whatever and place a toddler with a rope tied to the end of the plane's nose in front of the plane. The toddler will not be able to pull the plane and keep it moving, instead, the rolling friction between the wheels of the plane and the ground will slow the plane to a stop in very short order.

You say that "You want friction with the ground when the plane is trying to take off, this allows it to accelerate. "

This would be true only if the plane were propelled by its wheels - which you agree is not the case.
No, it's because the wheels push backwards against the ground in order to move the object they are attached to (the plane) forwards. It's the same principle as with a car.

No it won't. There is a force of friction between the wheels on the airplane and the ground. If there wasn't, then a toddler could push the plane down the runway. Hell, if there wasn't any friction between the wheels of the plane and the ground then the plane would never go anywhere to begin with.


No shit it's not propelled by its wheels, its wheels don't have little engines. That doesn't mean that the wheels aren't attached to the plane and touching the ground. It also doesn't mean that the wheels do not experience a frictional force with respect to the ground.


I don't think they wheels on a plane are functioning to minimize friction with respect to the ground. You want friction with the ground when the plane is trying to take off, this allows it to accelerate.


Umm... no.

Oh boy we've got a live one! Little Miss Dakini will have a red face tonight :)


1) A car is propelled by friction between its wheels and the ground, the wheels 'pull' the car along by 'gripping' the surface - this is the source of a car's forward motion, do you understand and agree or not?

2) A plane is propelled forward by its engines acting on the air, it is pushed along by thrust coming out of the back of the jet engines, or else pulled along by the propellers moving through the air and creating 'lift' on the horizontal - do you understand and agree or not?

3) A plane's wheels do not deliver the force of its engine to the ground in the same way that a car's wheels do. Do you understand and agree or not?

4) You say that if there were no friction between the plane and the ground that a toddler could push it. Then you say that it couldn't go anywhere. Those two statements are diametrically opposed. Which is it?

5) How can a plane take off from water without wheels? How can a plane take off from ice without wheels?

6) You don't think that the wheels on a plane function to minimize friction with the ground - you're incorrect, so think again - this question is not a matter of opinion.

No it won't. There is a force of friction between the wheels on the airplane and the ground. If there wasn't, then a toddler could push the plane down the runway. Hell, if there wasn't any friction between the wheels of the plane and the ground then the plane would never go anywhere to begin with.


No shit it's not propelled by its wheels, its wheels don't have little engines. That doesn't mean that the wheels aren't attached to the plane and touching the ground. It also doesn't mean that the wheels do not experience a frictional force with respect to the ground.


I don't think they wheels on a plane are functioning to minimize friction with respect to the ground. You want friction with the ground when the plane is trying to take off, this allows it to accelerate.


Umm... no.

Oh boy we've got a live one! Little Miss Dakini will have a red face tonight :)


1) A car is propelled by friction between its wheels and the ground, the wheels 'pull' the car along by 'gripping' the surface - this is the source of a car's forward motion, do you understand and agree or not?

2) A plane is propelled forward by its engines acting on the air, it is pushed along by thrust coming out of the back of the jet engines, or else pulled along by the propellers moving through the air and creating 'lift' on the horizontal - do you understand and agree or not?

3) A plane's wheels do not deliver the force of its engine to the ground in the same way that a car's wheels do. Do you understand and agree or not?

4) You say that if there were no friction between the plane and the ground that a toddler could push it. Then you say that it couldn't go anywhere. Those two statements are diametrically opposed. Which is it?

5) How can a plane take off from water without wheels? How can a plane take off from ice without wheels?

6) You don't think that the wheels on a plane function to minimize friction with the ground - you're incorrect, so think again - this question is not a matter of opinion.

The toddler can't push the plane because of inertia, not friction.
Uh.... seriously?
What level of physics have you attained? Inertia states that an object in motion will stay in motion or an object at rest will stay at rest unless acted upon by an outside force. A toddler pulling an airplane would be an outside force.

Ok, so you have a force of static friction which is described by F_f=u_s*F_N (pretend the u is a mu, I can't do greek letters here). F_N is exactly equal and opposite to F_g, the force of gravity on the airplane (which can be approximated to be described as F_g=mg, where m is the mass of the airplane and g is ~ -9.8m/s^2). Now let's say that the airplane's mass is on the order of 10,000 kg and u_s is on the order of 1, the child would need to generate 10,000N of force to move the airplane, which a child with a mass on the order of ~10kg would not be able to do.

If you want, we can do a simpler system which removes your intertia argument altogether. Let's say we have a plane in motion (very slow motion) and we turn off its thrusters or remove the taxi or whatever and place a toddler with a rope tied to the end of the plane's nose in front of the plane. The toddler will not be able to pull the plane and keep it moving, instead, the rolling friction between the wheels of the plane and the ground will slow the plane to a stop in very short order.

You say that "You want friction with the ground when the plane is trying to take off, this allows it to accelerate. "

This would be true only if the plane were propelled by its wheels - which you agree is not the case.
No, it's because the wheels push backwards against the ground in order to move the object they are attached to (the plane) forwards. It's the same principle as with a car.

USnip
No, it's because the wheels push backwards against the ground in order to move the object they are attached to (the plane) forwards. It's the same principle as with a car.

Except a cars engine pushes the wheels <----- which makes the ground push ----> which then moves the car

An airplane does not have an engine to push <----- on the ground any more then a soapbox car does

It uses Its jet engines to act using the air to create forward thrust

No, it's because the wheels push backwards against the ground in order to move the object they are attached to (the plane) forwards. It's the same principle as with a car.

Oh my god.

Uh.... seriously?
What level of physics have you attained? Inertia states that an object in motion will stay in motion or an object at rest will stay at rest unless acted upon by an outside force. A toddler pulling an airplane would be an outside force.


No, it's because the wheels push backwards against the ground in order to move the object they are attached to (the plane) forwards. It's the same principle as with a car.

What level of physics have you attained? Another play-acting physicist getting uppity and arrogant...

The wheels do not push backward against the ground in order to move an airplane, it is a different principle from a car. Notice how you don't see many cars flying around? Why is that I wonder :rolleyes: ?

If a plane were propelled by its wheels pushing against the ground, it would not be able to move forward in the air. You're completely wrong.

What level of physics have you attained? :rolleyes: :D :D :) :D :D

What level of physics have you attained? Another play-acting physicist getting uppity and arrogant...

The wheels do not push backward against the ground in order to move an airplane, it is a different principle from a car. Notice how you don't see many cars flying around? Why is that I wonder :rolleyes: ?

If a plane were propelled by its wheels pushing against the ground, it would not be able to move forward in the air. You're completely wrong.

What level of physics have you attained? :rolleyes: :D :D :) :D :D

Ok lets settle down I agree with you on the topic but this is not going to help lets just chill ok?

Dakini as well? ok

Oh boy we've got a live one! Little Miss Dakini will have a red face tonight :)
Unlikely, seeing as I discussed this with a colleague who is also a graduate student in physics and I'm heading to bed as soon as I'm done this post.

1) A car is propelled by friction between its wheels and the ground, the wheels 'pull' the car along by 'gripping' the surface - this is the source of a car's forward motion, do you understand and agree or not?

2) A plane is propelled forward by its engines acting on the air, it is pushed along by thrust coming out of the back of the jet engines, or else pulled along by the propellers moving through the air and creating 'lift' on the horizontal - do you understand and agree or not?

3) A plane's wheels do not deliver the force of its engine to the ground in the same way that a car's wheels do. Do you understand and agree or not?
I agree, but none of this is relevant, the force of friction still acts between the wheels of the plane and the ground.

4) You say that if there were no friction between the plane and the ground that a toddler could push it. Then you say that it couldn't go anywhere. Those two statements are diametrically opposed. Which is it?
I said that it wouldn't go anywhere because there is friction between the ground and the airplane. Another poster was suggesting that friction was irrelevant. Please keep track of what I say before you put words in my mouth that make me sound like a moron.

5) How can a plane take off from water without wheels? How can a plane take off from ice without wheels?
You know that friction exists on both water and ice, correct?

6) You don't think that the wheels on a plane function to minimize friction with the ground - you're incorrect, so think again - this question is not a matter of opinion.
That doesn't mean that friction still doesn't exist and isn't large.

Also, I don't see what anything you said has to do with anything.

Ok, so here's the set up.
You have a plane facing the positive x direction, let's call this "left". You have a runway moving in the negative x direction, let's call this "right" with a velocity -v which is equivalent to the required takeoff wind velocity of the aircraft.
Now, the plane is starting from rest, which means that for much of the time it spends accelerating, it is still going in the negative x direction until its velocity reaches the normal takeoff velocity, at which point its velocity relative to the ground and the air will be 0. From here on out, the thrusters will be applying additional force in order to accelerate the aircraft further. It won't be twice the required force for a normal takeoff, but it will still be greater and in the end, the aircraft will have accelerated to a higher velocity relative to its moving runway than it will have moved relative to a stationary one.

What level of physics have you attained? Another play-acting physicist getting uppity and arrogant...
No, a real physicist who doesn't pay attention to airplanes.

The poster poorly defined inertia, what reaction do you expect?

The wheels do not push backward against the ground in order to move an airplane, it is a different principle from a car. Notice how you don't see many cars flying around? Why is that I wonder :rolleyes: ?
You do know why they put spoilers on racecars, right?

Also, when the plane is on the ground, the wheels do so push backwards against the ground. This might not be what accelerates the plane, but it still happens, I'm pretty sure this is what happens for wheels, but I'm too tired to work out all possible wheel systems right now and really don't care that much about an internet debate to do so.

What level of physics have you attained?
Hons. BSc. with a specialization in Astrophysics.

It's velocity relative the ground is meaningless. Only it's velocity to the air around the plane is meaningful. The treadmill does virtually nothing to slow the plane in relation to the air or a fixed point on the ground.
The treadmill moves the plane backwards until the plane matches the speed of the treadmill.
I would call this significant.

Except a cars engine pushes the wheels <----- which makes the ground push ----> which then moves the car

An airplane does not have an engine to push <----- on the ground any more then a soapbox car does

It uses Its jet engines to act using the air to create forward thrust
Yeah, poor phrasing. Sorry. I was woken up by construction at 5 am (they apparently wanted to reopen an intersection before rush hour) and it's now midnight.

Also, thank you for not being a total jerk like the other posters who pointed this out.

No, a real physicist who doesn't pay attention to airplanes.

The poster poorly defined inertia, what reaction do you expect?


You do know why they put spoilers on racecars, right?


Hons. BSc. with a specialization in Astrophysics.


Oh Jesus Christ this is just too rich! Do they put spoilers on race cars so that they don't fly away to Spain? hahaha

Run, don't walk, to the physics department of your university and exclaim "Racecars can fly because their wheels provide thrust in the air! using magic!" Video tape it and post the looks on their faces.

In astrophysics school do they forget to mention how a plane is propelled? You know, by a jet. Not by wheels...

Yeah, poor phrasing. Sorry. I was woken up by construction at 5 am (they apparently wanted to reopen an intersection before rush hour) and it's now midnight.

Also, thank you for not being a total jerk like the other posters who pointed this out.

I want to debate over it :) Not get angry over it ... Its a long night for me too and I dont need my temper going up

people are making this way too complicated as it needs to be. too complicated = too many questions = makes 55% of poeple on the poll wrong. the treadmill could be going 1000 x the takeoff velocity of the plane and it can still take off. the foreward thrust of the engines isn't bases upon the speed of the treadmill. it's independant!!! if the treadmill was going in the same direction at 10000 times the takeoff velocity it wouldn't propel the plane forward.. why? wheels and thrust independant of the treadmill......

Oh Jesus Christ this is just too rich! Do they put spoilers on race cars so that they don't fly away to Spain? hahaha
No, they put spoilers on racecars to keep them on the ground. They're much more aerodynamic than regular cars.
pwnage (http://www.fi.edu/wright/again/wings.avkids.com/wings.avkids.com/Book/Sports/advanced/racecar-01.html)
They won't fly to Spain, but they will leave the ground if they hit a certain velocity without a spoiler. They'll probably flip over and crash shortly after leaving the ground, but that's not related to their wheels being propelled by their engines, that's probably related to poor balance and such, I also haven't studied the aerodynamics of racecars.

In astrophysics school do they forget to mention how a plane is propelled? You know, by a jet. Not by wheels...
Contrary to popular belief, astrophysicists look at interesting problems, not how planes fly. I don't care about the intricate details of how the plane flies so long as it gets me to my telescope in Hawaii.

Unlikely, seeing as I discussed this with a colleague who is also a graduate student in physics and I'm heading to bed as soon as I'm done this post.


I agree, but none of this is relevant, the force of friction still acts between the wheels of the plane and the ground.


I said that it wouldn't go anywhere because there is friction between the ground and the airplane. Another poster was suggesting that friction was irrelevant. Please keep track of what I say before you put words in my mouth that make me sound like a moron.


You know that friction exists on both water and ice, correct?


That doesn't mean that friction still doesn't exist and isn't large.

Also, I don't see what anything you said has to do with anything.

Ok, so here's the set up.
You have a plane facing the positive x direction, let's call this "left". You have a runway moving in the negative x direction, let's call this "right" with a velocity -v which is equivalent to the required takeoff wind velocity of the aircraft.
Now, the plane is starting from rest, which means that for much of the time it spends accelerating, it is still going in the negative x direction until its velocity reaches the normal takeoff velocity, at which point its velocity relative to the ground and the air will be 0. From here on out, the thrusters will be applying additional force in order to accelerate the aircraft further. It won't be twice the required force for a normal takeoff, but it will still be greater and in the end, the aircraft will have accelerated to a higher velocity relative to its moving runway than it will have moved relative to a stationary one.

You said that a plane operates on the same principle as a car, that its wheels use friction to propel it forward. This is wrong.

The engines on a plane are what provide forward thrust to it, not the rotation of the wheels. The wheels are incidental, they are only there to minimize friction between the plane and the ground. On ice, stationary skis or skids can replace the wheels, because the wheels play no role in propelling the plane, and the skis sufficiently minimize the friction between the plane and the ice.

What is more, as Myrmidosia, a real-life professional, has already explained further back in the thread that the plane's ability to overcome the rolling friction necessary to make it move forward in normal circumstances is proof that it can take off from a treadmill.

When I told you to read back in the thread and recant, it wasn't because I disagreed with your opinion, it was because you are factually in error. So go do it. Maybe you'll attain a higher level of physics. :rolleyes:

No, a real physicist who doesn't pay attention to airplanes.

The poster poorly defined inertia, what reaction do you expect?


You do know why they put spoilers on racecars, right?

Also, when the plane is on the ground, the wheels do so push backwards against the ground. This might not be what accelerates the plane, but it still happens, I'm pretty sure this is what happens for wheels, but I'm too tired to work out all possible wheel systems right now and really don't care that much about an internet debate to do so.


Hons. BSc. with a specialization in Astrophysics.

Actually with plane wheels it is the opposite of car wheels as far as direction of force applied

The plane goes forward which makes the wheels (with inertial laws intact and the wheels resisting initial rotation and acceleration) push ---> on the ground and the ground push<----- back making them spin

Where as a car pushes on its wheels <----- which makes the ground push ---->

But yeah they push against the ground to resist the change but not in the same way and not providing the motive force in this case

why? wheels and thrust independant of the treadmill......
No they're not! Just because something isn't attached to something else doesn't make it independent! There is still a frictional force and if you add this to the fact that putting an object on a non-accelerating treadmill (i.e. one that is moving at a constant velocity) will cause it to move in the direction of the treadmill motion, regardless of whether or not it has wheels.

No, they put spoilers on racecars to keep them on the ground. They're much more aerodynamic than regular cars.
pwnage (http://www.fi.edu/wright/again/wings.avkids.com/wings.avkids.com/Book/Sports/advanced/racecar-01.html)
They won't fly to Spain, but they will leave the ground if they hit a certain velocity without a spoiler. They'll probably flip over and crash shortly after leaving the ground, but that's not related to their wheels being propelled by their engines, that's probably related to poor balance and such, I also haven't studied the aerodynamics of racecars.


Contrary to popular belief, astrophysicists look at interesting problems, not how planes fly. I don't care about the intricate details of how the plane flies so long as it gets me to my telescope in Hawaii.



A car can leave the ground momentarily, lose control and crash (hence the spoiler, if I understand the airplane on the treadmill I obviously understand spoilers :) ) but it cannot fly like an airplane because it does not have a mechanism to provide forward motion in the air, because it operates on a different principle than an airplane, because an airplane is not propelled forward by its wheels, and as a result can take off from a treadmill.

Recant and attain the next level of physics!

No they're not! Just because something isn't attached to something else doesn't make it independent! There is still a frictional force and if you add this to the fact that putting an object on a non-accelerating treadmill (i.e. one that is moving at a constant velocity) will cause it to move in the direction of the treadmill motion, regardless of whether or not it has wheels.

ok maybe not totally independant, but i'm trying to simplify this. the longer this goes, the more people are writing books in this post. the bottom line is that the plane will take off, and the wheels aren't supplying the velocity for takeoff. the engine is... so plane goes bye..bye

You said that a plane operates on the same principle as a car, that its wheels use friction to propel it forward. This is wrong.
I admitted this. I also admitted that it's been a long day to the one poster who hasn't been a total douche.

The engines on a plane are what provide forward thrust to it, not the rotation of the wheels. The wheels are incidental, they are only there to minimize friction between the plane and the ground.
That doesn't mean that they eliminate friction.

What is more, as Myrmidosia, a real-life professional, has already explained further back in the thread that the plane's ability to overcome the rolling friction necessary to make it move forward in normal circumstances is proof that it can take off from a treadmill.
Ok? I already said that it could make it off a treadmill. It would just require more force from the thrusters because it would need to be accelerated more to overcome the fact that it would start off with a negative velocity. Look at my second post in this thread. Thanks.

When I told you to read back in the thread and recant, it wasn't because I disagreed with your opinion, it was because you are factually in error. So go do it. Maybe you'll attain a higher level of physics. :rolleyes:
Yeah, that's why I'm in grad school. Except that again, I'll be studying something that is actually interesting, not how planes fly.

ok maybe not totally independant, but i'm trying to simplify this. the longer this goes, the more people are writing books in this post. the bottom line is that the plane will take off, and the wheels aren't supplying the velocity for takeoff. the engine is... so plane goes bye..bye
Yeah. That doesn't mean that the lack of a stationary runway is irrelevant and if the plane were to only accelerate normally it wouldn't takeoff.

A car can leave the ground momentarily, lose control and crash (hence the spoiler, if I understand the airplane on the treadmill I obviously understand spoilers :) ) but it cannot fly like an airplane because it does not have a mechanism to provide forward motion in the air, because it operates on a different principle than an airplane, because an airplane is not propelled forward by its wheels, and as a result can take off from a treadmill.
Note my earlier statement that wheels on a plane do preform a different function than wheels on a car. Thanks.

Recant and attain the next level of physics!
This is an aside that has nothing to do with the initial question. And stop being rude.

I'm going to bed. I don't need to deal with this shit.

Yeah. That doesn't mean that the lack of a stationary runway is irrelevant and if the plane were to only accelerate normally it wouldn't takeoff.

ok two people agreed.... it must be true then... the plane will take off... can't we all just get along???

No they're not! Just because something isn't attached to something else doesn't make it independent! There is still a frictional force and if you add this to the fact that putting an object on a non-accelerating treadmill (i.e. one that is moving at a constant velocity) will cause it to move in the direction of the treadmill motion, regardless of whether or not it has wheels.

The force exerted on the plane by the wheel axles and bearings is orders of magnitude smaller than the force exerted by the jet engines.

Even if the runway is moving, the extra force applied is inconsequential compared to the grossly unbalanced force that the jets provide, which pushes the plane forward. A plane with its engines turned off would be stationary on the treadmill and move backwards along with it, but once the engines turned on the plane would begin to roll forward as a hugely unbalanced force was applied.

The force exerted on the plane by the wheel axles and bearings is orders of magnitude smaller than the force exerted by the jet engines.

Even if the runway is moving, the extra force applied is inconsequential compared to the grossly unbalanced force that the jets provide, which pushes the plane forward. A plane with its engines turned off would be stationary on the treadmill and move backwards along with it, but once the engines turned on the plane would begin to roll forward as a hugely unbalanced force was applied.
Clearly you didn't pay attention to what I said. If you take a plane. Just a plane. One that does not have its thrusters turned on. You place this plane on a runway that is moving backwards. The plane will move backwards with the runway.

Now I'm going to bed.

No they're not! Just because something isn't attached to something else doesn't make it independent! There is still a frictional force and if you add this to the fact that putting an object on a non-accelerating treadmill (i.e. one that is moving at a constant velocity) will cause it to move in the direction of the treadmill motion, regardless of whether or not it has wheels.
True the question is will that friction will be enough to over come the thrust

We agree that in an ideal situation (no friction) there would be NO change from normal (with respect to the earth) in takeoff right?

Now it is only the force imparted (using friction) on the plane ... with most planes having extra capacity (in any comercial situation there should be no need to redline it for takeoff) and with the length of the runway not limited (so if it had to take longer to accelerate to speed it could) the planes for the MOST part should be alright with taking off even if their flight profile is not exactly norm


But in the end if we were going to be that pedantic about increased rolling friction we may also look into the fact that the belt may be causing the air to move WITH the belt therefore giving the plane increased headwind (which in turn may be enough to negate the increased friction)

(Just another factor)

It's a simple answer. Without any air flow under the wings, it cannot be lifted. Airplanes don't drive, the wheels have no effect on takeoff, besides transporting the plane on the ground until it does takeoff.

Will a guy walking the wrong direction on an escalator go anywhere?

Will a guy walking the wrong direction on an escalator go anywhere?

He would if he had a jet engine strapped to his back.

How in-the-living-fuck did this thread garner 25 pages? :confused:

All the jet engines do on a treadmill is like a guy running on one, keeps it in place

When a jets engines start, the plane SLOWLY starts to creep forward before it starts gaining speed, and the amount of length that it goes increases the airflow under the wings, that creates lift, and the plane starts to get enough airflow and speed that it can lift off the ground and fly

Also, to those of you that think the plane will travel down the treadmill and takeoff just like a normal runway, if the wheels are moving the exact opposite speed, the plane will not move, so you are assuming that the plane simply floats off the treadmill.

Let's view it from the dunces perspective now.
Lets say even though the treadmill is going the same speed in the opposite direction, lets assume that the jets makes the plane take off without moving any length. What will keep it from falling out of the sky the moment it gets off the ground due to lack of airspeed?

Don't try to tell me that jets will make it out speed the treadmill, a plane weighs a lot and there is too much friction for the wheels to simply slide down the treadmill. RC Planes are not valid proof because the fact that the propulsion to weight ratio is extremely different than a real plane. An RC plane with an engine that is the same size as the rest of the plane (which is probably made out of foam), will take off much much faster than a real plane. Notice how these planes take off, and tell me if they look like they have enough speed to simply shoot off a treadmill without the wheels friction slowing them down.

http://youtube.com/watch?v=Z5XXTkQX-W0 (Plane Takeoff)

Now had it been on a giant treadmill, it would never have gone forward, therefore it would never gain the speed that creates the air flow under the wing, which is why it took off.

How in-the-living-fuck did this thread garner 25 pages? :confused:


This is a highly-charged emotional issue.

How in-the-living-fuck did this thread garner 25 pages? :confused:

Many people form strong opinions about problems that they are either too confused, ignorant, or unintelligent to understand sufficiently.

The plane on a treadmill is an excellent experiment to demonstrate this- look at the arrogant certainty which some people in this thread have put on when promoting their false beliefs. Frequently we have seen education touted as a credential, the classic fallacy of appealing to authority.

The people who held the wrong idea and then recanted and understood the truth stand to gain more from this thread than anyone else, since they can look back and see how sure the were, in spite of being completely in error. Let's hope they, and the rest of the people on NSG, take some time to think to themselves: "Maybe I'm wrong about other things, too, and don't even know it." Many of us are, and about much more important topics than airplanes.

Bear in mind, the majority of people who voted here are wrong (a fact which is not open to debate) - even though the correct answer was presented in the very first reply.

The only problem with this thread, and one I apologized for already and will do again, is that I foolishly neglected to tick the 'make results public' box when putting up the poll. That list would be telling.

Many people form strong opinions about problems that they are either too confused, ignorant, or unintelligent to understand sufficiently.

The plane on a treadmill is an excellent experiment to demonstrate this- look at the arrogant certainty which some people in this thread have put on when promoting their false beliefs. Frequently we have seen education touted as a credential, the classic fallacy of appealing to authority.

The people who held the wrong idea and then recanted and understood the truth stand to gain more from this thread than anyone else, since they can look back and see how sure the were, in spite of being completely in error. Let's hope they, and the rest of the people on NSG, take some time to think to themselves: "Maybe I'm wrong about other things, too, and don't even know it." Many of us are, and about much more important topics than airplanes.

Bear in mind, the majority of people who voted here are wrong (a fact which is not open to debate) - even though the correct answer was presented in the very first reply.
For a short time the Yes option was in the lead but the somehow it dropped again. I would have expected that in the end the Yes option would win by a wide margin (when all the folks would have finally understood the matter). The poll result as it is now is pretty disappointing (80 yes, 95 no).

The only problem with this thread, and one I apologized for already and will do again, is that I foolishly neglected to tick the 'make results public' box when putting up the poll. That list would be telling.Indeed.

The people who held the wrong idea and then recanted and understood the truth stand to gain more from this thread than anyone else, since they can look back and see how sure the were, in spite of being completely in error.

That happened to me on the last one of these things. I got it eventually. Of course, in that thread we didn't have youtube videos that clearly show a plane moving against a treadmill, so how people can continue to think it wouldn't happen is beyond me.

The only problem with this thread, and one I apologized for already and will do again, is that I foolishly neglected to tick the 'make results public' box when putting up the poll. That list would be telling.

It's been an interesting thread from the perspective of people who simply will not take the 2 seconds it would take to look up the answer, especially when getting into rebuttals. Why wouldn't you look for evidence to back your beliefs, at which point anyone would see they were wrong?

So I don't think it would indicate much to have made the poll public because I for one would have thought no, but on the first few rebuttals, thankfully before I put in a reply, I googled the answer and saw I was wrong in my assumption.

I do think those who knew the answers were purposely vague in some of their replies but really, it shouldn't have lasted beyond 3 pages.

The issue is not whether people would be right or wrong, but whether they bother to actually check what they're saying, or at least look for evidence, rather than argue on and on from gut feeling.

the plane will takeoff. end of discusion........ why? because physics will allow it. why? arrg... take a physics class.

http://www.straightdope.com/columns/060203.html

What gets a plane moving are its propellers or jet turbines, which shove the air backward and thereby impel the plane forward. What the wheels, conveyor belt, etc, are up to is largely irrelevant. Let me repeat: Once the pilot fires up the engines, the plane moves forward at pretty much the usual speed relative to the ground--and more importantly the air--regardless of how fast the conveyor belt is moving backward. This generates lift on the wings, and the plane takes off. All the conveyor belt does is, as you correctly conclude, make the plane's wheels spin madly.

http://www.straightdope.com/columns/060303.html

But what if the treadmill continues to accelerate? Different story. In principle it's possible to accelerate the treadmill at a rate that will exactly counteract any forward force you care to apply. (This is a departure from the original question, which said the conveyor belt compensated for the plane's speed,, not its force.) The only mathematics needed to demonstrate this is the well-known physics axiom F = ma--that is, force equals mass times acceleration. Given that the conveyor exerts some backward force F on the plane, we simply crank up the acceleration as much as necessary to equal any forward force F generated by its engines. Result: The plane stands still and doesn't take off.

http://www.straightdope.com/columns/060203.html



http://www.straightdope.com/columns/060303.html

And that's totally irrelevant. Airplanes can't fly.

There are TWO debates running concurrently on this thread.

1) Will a plane, actively trying to take off from a treadmill moving in the opposite direction, take off.

and

2) Will a Plane sitting on a treadmill with it's engines off move with the treadmill.

before posters get into the area of flaming (I hope I'm not too late...) perhaps people need to reiterate which one they are arguing.

and if you want to know what started the second argument...
The wheels on a plane are not connected to a drive shaft like they are on a car. If you take a plane, with the engine OFF, and drop it on a treadmill, it won't go anywhere. The treadmill will move under the wheels, and the wheels will just...spin. The wheels aren't connected to any drive shaft, them spinning won't move the plane. The treadmill will just cause the wheels of the plane to spin, but the plane, with it's engine off, won't move.

When the plane turns its engine on and begins moving forward, again, the treadmill will do nothing. A plane is not driven by its wheels, it is driven by its turbine. The wheels merely serve to reduce friction with the ground.

I believe Dakini is focusing on the second argument, and so was Neo Art and I. however I think some people mistakenly view us discussing the first argument.


ok two people agreed.... it must be true then... the plane will take off... can't we all just get along??? sit back and relax KuQee... enjoy the ride and remember to mind the no smoking and fasten seat belts signs. the flight attendants will be serving drinks in a moment...

Contrary to popular belief, astrophysicists look at interesting problems, not how planes fly. I don't care about the intricate details of how the plane flies so long as it gets me to my telescope in Hawaii.we would prefer the plane takes you to the Airport in Hawaii... the landing at the telescope is a bit... short, abrupt, and for some reasons, irritates the Nenes. :p

Those two questions are intrinsically related. IF the plane remains stationary on the moving treadmill, with its engines off, then it will be able to take off without any problem, with the engines on.

Overarching the entire discussion is one fundamental question, will the plane, without any thrust from its engines, move backwards on the treadmill?

The answer, for the most part, is no, it will not. This is, of course, in a hypothetical assuming no friction. If we go back to the "real world", then the answer is yes, but not very much.

Once we include friction into it, the plane will move backwards with the treadmill...slightly. Nowhere near the full speed of the treadmill however.

The hypothethical said the treadmill moving at the same speed as the plane's takeoff speed. THe presumption by some is that they will effectively cancel out, and the plane, with thrust, will remain stationary. This is patently untrue. Friction on the wheel from the treadmill will cause a bit of drag back, because friction between the wheel and the axil means it can't turn 100% freely, but it's only a slight amount, and certainly enough for any airplane to overcome.

Those two questions are intrinsically related. IF the plane remains stationary on the moving treadmill, with its engines off, then it will be able to take off without any problem, with the engines on.

Overarching the entire discussion is one fundamental question, will the plane, without any thrust from its engines, move backwards on the treadmill?

The answer, for the most part, is no, it will not. This is, of course, in a hypothetical assuming no friction. If we go back to the "real world", then the answer is yes, but not very much.

Once we include friction into it, the plane will move backwards with the treadmill...slightly. Nowhere near the full speed of the treadmill however.

The hypothethical said the treadmill moving at the same speed as the plane's takeoff speed. THe presumption by some is that they will effectively cancel out, and the plane, with thrust, will remain stationary. This is patently untrue. Friction on the wheel from the treadmill will cause a bit of drag back, because friction between the wheel and the axil means it can't turn 100% freely, but it's only a slight amount, and certainly enough for any airplane to overcome.Nicely put, I would add in the example of those performers who can remove a tablecloth without significantly disturbing the crockery, cutlery and glassware.

Those two questions are intrinsically related. IF the plane remains stationary on the moving treadmill, with its engines off, then it will be able to take off without any problem, with the engines on. related yes, but still different because the fact of the status of the engine is very important.

Overarching the entire discussion is one fundamental question, will the plane, without any thrust from its engines, move backwards on the treadmill?actually, the second discussion is without thrust from the engine.

The answer, for the most part, is no, it will not. This is, of course, in a hypothetical assuming no friction. If we go back to the "real world", then the answer is yes, but not very much.

Once we include friction into it, the plane will move backwards with the treadmill...slightly. Nowhere near the full speed of the treadmill however. yep. once friction is applied. but without friction, nothing would move as the treadmill will slide below the object. be it a car, or a boat, or even a person. without friction, even the plane's wheels won't turn. ;)

The hypothethical said the treadmill moving at the same speed as the plane's takeoff speed. THe presumption by some is that they will effectively cancel out, and the plane, with thrust, will remain stationary. This is patently untrue. Friction on the wheel from the treadmill will cause a bit of drag back, because friction between the wheel and the axil means it can't turn 100% freely, but it's only a slight amount, and certainly enough for any airplane to overcome. and that is the first argument. but I just wanted to show people that there were TWO arguments that were similar yet different to avoid misunderstandings and hard feelings. ;)

Once we include friction into it, the plane will move backwards with the treadmill...slightly. Nowhere near the full speed of the treadmill however.

That would depend on the acceleration rather than speed of the treadmill.

Also the pressure in the tires is not "hard" but relatively soft causing sizeable amount of friction necessary during landing phase.

In case of a plane on a treadmill and slowly accelerating belt the speed of the plane would be at first be equal to the speed of the treadmill because the air resistance would be less than the maximum force conveyed by the non-rotating tire - After a certain limit the plane's backward acceleration would slow down, perhaps turning negative, as the wheels begin to spin until reaching absolute equilibrium between air resistance and the force conveyed through the tires.

I'd say that due to the aerodynamic shape of the plane the maximum speed of a freestanding plane on a treadmill could be in range of hundreds of kilometers/hour, depending on the plane.

A relevant article:
http://www.volkswatch.com/vwnews/touaregtowsboeing747.asp

A 230 kilowatt (308 hp) car is able to tow 747 at a speed of ~10 kilometers per hour when the only significant resistance is the resistance conveyed through the tires.

It's been an interesting thread from the perspective of people who simply will not take the 2 seconds it would take to look up the answer, especially when getting into rebuttals. Why wouldn't you look for evidence to back your beliefs, at which point anyone would see they were wrong?

So I don't think it would indicate much to have made the poll public because I for one would have thought no, but on the first few rebuttals, thankfully before I put in a reply, I googled the answer and saw I was wrong in my assumption.

I do think those who knew the answers were purposely vague in some of their replies but really, it shouldn't have lasted beyond 3 pages.

The issue is not whether people would be right or wrong, but whether they bother to actually check what they're saying, or at least look for evidence, rather than argue on and on from gut feeling.
I'm truly amazed that we've seen over 375 posts and the thread is still on topic, by and large. In an effort to remedy that, I'll continue rambling...

I remember reading a satire one time that talked about liftee molecules. It was hilarious, but I can't seem to find it published on line. I do remember it was important not to tip the wing up too high, or they would all roll off -- causing what's known as a "stall", i.e. the loss of lift.