Comments on Airplane on a Treadmill: Airplane on a treadmill

...how did that 'ctor' get there?

2010-03-07T12:06:25.189-05:00

...how did that 'ctor' get there?

Of course, if the plane was a weird model that, wh...

2010-03-07T12:05:06.777-05:00

Of course, if the plane was a weird model that, while it's on the ground, moves like a car, and changed to propeller/jet once in the air, you would be able to stop it. This would also work with a car.

Am I correct in this?
Assuming I am, all my confusion in this matter has been resolved, so thank you.ctor

"So if you were to ponder putting a plane on a tre...

2010-02-13T11:42:31.250-05:00

"So if you were to ponder putting a plane on a treadmill, isn't it inherent to the question that the plane will remain stationary to the ground?"

No. If the plane being stationary to the ground were the important part, they would have picked a mechanism that would actually keep it stationary, such as large fixed blocks in front of all of the wheels - or maybe even removing the wheels completely, and replacing them with long poles in holes in the ground.

"The intent of the question is to test a person's knowledge of lift, not the detailed physics of putting a wheeled object on a treadmill."

Wrong. The intent of the question is to test a person's knowledge of force and motion. When you or I are walking, we exert a force on the ground to accelerate. The treadmill counters this force, and prevents our acceleration. Planes do not push on the ground to accelerate, and so a treadmill would not be able to cancel their force, and would not prevent their acceleration.

This question isn't about a "wheeled object" on a treadmill, because a car is a wheeled object that would be held stationary by a treadmill. It's about an object that doesn't use the ground to accelerate on a treadmill, and it checks whether or not you can realize that difference.

Or, you change the premise and talk about a mile-l...

2010-02-13T10:18:48.353-05:00

Or, you change the premise and talk about a mile-long treadmill and now you're into the difference between applying force to the wheels vs. to the object itself. But if you want that answer, why not just replace the treadmill with an iced over runway? A car would sit and spin, and so would my legs, but a plane would still take off. A good question, indeed, but not if you use the premise of a treadmill.

When I run on a treadmill, I remain stationary com...

2010-02-13T09:58:46.626-05:00

When I run on a treadmill, I remain stationary compared to the ground. So if you were to ponder putting a plane on a treadmill, isn't it inherent to the question that the plane will remain stationary to the ground? The intent of the question is to test a person's knowledge of lift, not the detailed physics of putting a wheeled object on a treadmill. So the answer is "No, a plane cannot take off on a treadmill." To answer it any other way is to be an ass.

I saw the MythBusters episode having never heard o...

2010-01-29T20:27:57.161-05:00

I saw the MythBusters episode having never heard of the debate before and must confess I thought it wouldn't fly. Like you state though, the main reason for this was how I interpreted the question. The MythBusters used a graphic to help explain the thought experiment which probably did more harm than good because it made it seem as if they expected the plane to take off from a stationary state. I understand your friction arguement and agree that if the plane wants to it would overcome friction and move.

A better experiment would be to attach a propeller or jet to a model car with no gears to show that no matter how fast you make the treadmill go you can make the car move forward without the distraction of flight, plus four wheels are a lot more stable then the wheels on that sad model plane the MythBusters used.

Hey Anonymous, How many factors do you want to le...

2009-09-30T06:40:03.836-04:00

Hey Anonymous,

How many factors do you want to leave out here? If you leave in physics and aerodynamics, and don't tie the aircraft to a stationary object, it will depart when the engine is started and the throttle firewalled, regardless of what the conveyorbelt is doing...

Hey anonymous... what is the mechanism by which th...

2009-09-29T20:10:59.903-04:00

Hey anonymous... what is the mechanism by which the thrust from the engines is counteracted by the treadmill?

If the plane is not moving, how does it have a speed to be measured and matched?

The planes moves as normal, it's wheels spin at twice the speed, and it takes of pretty much normally.

it's an abstract thought experiment. the assumptio...

2009-09-29T20:08:30.579-04:00

it's an abstract thought experiment. the assumption is that the conveyor belt matches the plane's speed ALL. THE. TIME. get it? no humans involved. just abstract function "plane goes with y speed, conveyor goes with x=y speed". in this case, the plane will not move against the air, which results with no air flow around the wings, resulting in the plane remaining stationary till the world ends. the mythbusters argument lets it take off only in flawed, real life conditions. i repeat again, this is a thought experiment, things like human error, material imperfections and data transfer lag do not apply here.

The military already answered this question in 196...

2009-09-22T11:11:21.753-04:00

The military already answered this question in 1967 with the Custer Channel Wing Hybrid Jet. This is the full video.

http://www.youtube.com/watch?v=-Sn5JL9t_C4&feature=related

And this is an explanation by the inventor.

http://www.youtube.com/watch?v=7FhFlxbV-AU&feature=related

Please spread the word, no need to argue whats already been solved.

I'm pretty sure that anyone that argues that the p...

2009-09-13T02:31:52.901-04:00

I'm pretty sure that anyone that argues that the plane doesn't move is just trying to egg folks on. It just *has* to all be a big joke, because no one can be that ignorant after reading all the evidence.

Although there is the argument of...

Well Cameron... Unless you are able to produce a ...

2009-08-26T13:50:44.606-04:00

Well Cameron... Unless you are able to produce a compelling arguement for your statement, i'll consider your statement to be a product of lack of intelligence...

I disagree with you. The airplane would not take o...

2009-08-26T03:54:12.218-04:00

I disagree with you. The airplane would not take off.

Unbelievable. Does this never end? Anonymous: The...

2009-06-11T15:42:45.369-04:00

Unbelievable. Does this never end?

Anonymous: The plane still moves. Think about it:

The plane moves forward at speed x relative to the ground. The control system measures speed x, and drives the belt backward at speed x relative to the ground.

The speeds are matched, and the plane is still moving at speed x relative to the ground because the SPEED doesn't matter to the plane! The free-spinning wheels, which have nothing to do with the plane's propulsion, take away almost all of the friction between the belt and the plane and thus reduce the FORCE that the belt exerts on the plane to almost 0. The force exerted on the plane's engines GREATLY exceeds 0, and Newton's laws of motion take over. The plane has a net force, and so the plane moves. Period, end of story.

"This conveyor has a control system that tracks th...

2009-06-11T15:28:59.948-04:00

"This conveyor has a control system that tracks the plane speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction)."

Right there. Sure, that would actually be an impossible mechanism, however, if such a machine could be built the plane would not move. There is no one at the control of the treadmill, in the original question it says that it is tuned perfectly.

No, the only thing that can keep the aircraft from...

2009-05-09T17:43:14.089-04:00

No, the only thing that can keep the aircraft from going is a rope.

One last thing, there is an additional frictional ...

2009-05-09T17:06:56.512-04:00

One last thing, there is an additional frictional force in play in addition to the bearings which DOES increase with velocity.

The friction between the rubber tires and the road, called "rolling slip". This would, indeed, make it possible to have a conveyor run fast enough (albeit really flipping fast) to stop the plane!

Sorry, to clarify.. I think you've admirably prove...

2009-05-09T16:56:05.682-04:00

Sorry, to clarify.. I think you've admirably proven that it would be nigh on impossible for the conveyor belt to match the rotational speed of the free spinning wheels of a plane.

"It says that the conveyor belt must match the spe...

2009-05-09T16:53:47.656-04:00

"It says that the conveyor belt must match the speed of the plane.

What speed? If the plane stays stationary, there is no speed.

To have speed, the plane must already be moving and thus it cannot stay stationary."

Exactly, the entire statement is in semantics.

If I asked the original question, but replaced plane with car and asked if the car would move forward... the answer would be yes, the car moves forward. The belt and car will be moving X MPH, but the speedometer (rotational speed of the wheels) will be 2X.

I guess a way of rewording the question would be... if the conveyor exactly matches the rotational speed of the wheels, will the plane move? The answer would be no.

Awesome OP, pretty much the original question is really crappily worded and the answer boils down to semantics.

It's a scary thing, seeing so many idiots roam fre...

2009-04-14T16:59:15.146-04:00

It's a scary thing, seeing so many idiots roam free on the internet....

Yes, the aircraft will take off!

The velocity of the treadmill and wheels are irrelevant. The wheels are only there to keep the undercarriage from wearing down when on ground, and has nothing to do with propelling the aircraft forward.

My beautiful little Rans S-6ES (the bigger brother of the aircraft used by Mythbusters), with it's beautiful little engine, will start skidding with brakes on, on asphalt, with the engine running at about 2.000 rpm. At takeoff however, the engine runs at 3.300 rpm, and no realistic amount of friction caused by tires or bearings will keep it from getting airborne.
It simply can't be done...

Even in theory, the treadmill would always lag behind, because the wheels would be accelerating with the rate of the treadmill + the groundspeed of the aircraft In relation to the ground, not the treadmill).
The propeller and engine wouldn't care how fast the treadmill was going, because as far as they know, they are propelling the aircraft through the air.

The only way to keep the aircraft stationary on the treadmill is to tie it down, but then neither the wheels nor the treadmill would move, because the aircraft would be unable to initiate any movement of the wheels in the first place.

test

2009-02-24T16:13:55.598-05:00

test

The air flowing under the wings causes lift due to...

2009-02-19T10:47:56.977-05:00

The air flowing under the wings causes lift due to the shape of the wings.
Actually, it's OVER the wings that causes lift due to Bernoulli's principle... :)

If the plane is on a treadmill not moving through the air, the airspeed is theoretically zero under the wings.
That's a pretty big IF right there. Are you sure the plane won't be moving through the air?

Fact is, it will be. The wheels are free-spinning and the engines are "pushing against" the air, not the treadmill, and so the treadmill actually has almost no effect whatsoever on the plane's ability to move.

deathbytoaster, what you said about lift is true, ...

2009-02-18T22:37:51.649-05:00

deathbytoaster, what you said about lift is true, however you must keep the following in mind:

the plane is able to move relative the the wind, as its thrust comes from pushing against the wind. Regardless of what is underneath it, the plane pushes backwards on the wind, resulting in it moving forwards. Once it's moving forwards fast enough, it's able to take off due to the relative motion between the air and the wings.

The air flowing under the wings causes lift due to...

2009-02-18T22:30:04.451-05:00

The air flowing under the wings causes lift due to the shape of the wings. If the plane is on a treadmill not moving through the air, the airspeed is theoretically zero under the wings.Meaning there is NO LIFT. Whoever asked this question doesn't even have a clue what aerodynamics are.

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2009-02-05T11:34:00.000-05:00

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