You have a plane and a conveyor belt.

[unsped]

it seems that it would depends on the resistance of the wheel hub assemblies on the plane, as this will determine the amount of 'drag' on the plane.
if the wheel hubs has zero resistance, no matter what speed the belt was moving at the plane would stay stationary ... thus the existence of the conveyor belt has no affect on the planes ability to take off. there will exist an amount of wheel hub resistance that will create enough drag to not allow the plane to achieve proper wind speed.

QUESTION ANSWERED.

 

[EightySix Four]

For the people that don't get it:

It would be moving, remember a plane does not get thrust from it's wheels. the wheels will just move forward at twice the speed of the aircraft. if the plane hits 100mph, and the conveyor velt is going 100mph the other direction, total wheel speed will be 200mph, with air flowing over the wings at 100mph.

 

[So]

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THE PLANE WILL TAKE OFF...WE HAD HUNDREDS OF POSTS ON THIS! :|

 

[dug777]

No.

How does a plan work?

It's that whole airmovement over/under a curved surface that generates lift. we don't have that here. so no.

 

[EightySix Four]

Originally posted by: dug777
No.

How does a plan work?

It's that whole airmovement over/under a curved surface that generates lift. we don't have that here. so no.

WE DO HAVE AIRMOVEMENT... THE CONVEYOR BELT DOES NOTHING TO THE PLANE'S SPEED, IT JUST DOUBLES THE SPEED OF THE WHEELS. PLANE'S DO NOT PRODUCE THRUST FROM THEIR WHEELS... k?

 

[KK]

The conveyor belt will never keep going at the same pace that the plane is moving forward. It's impossible. It's like that .999999999=1 thing, the difference between that equals enough forward motion to move the plane forward thru the air.

So basically the OP's post is flawed from the get go.

 

[Shadowknight]

Harrier with vertical take-off, FTW.

 

[mugs]

Originally posted by: bctbct
No way the plane takes off. The conveyor keeps the plane from gaining forward motion...thus no air forms under the wing to cause lift.

I do have another question though.

A 85 yo guy told me once that he landed a plane flying backwards. He was a pilot in WWII, he said that he was landing a plane in a ninety mph head wind(someplace like Iceland or something) anyway since the headwind was faster than the landing speed, he considered it backwards. Thoughts?

Well... if his AIRSPEED was less than 90mph and the headwind was 90mph, then I guess the plane would have been moving backward. But where the hell was he landing, in a hurricane?

 

[waggy]

Originally posted by: dug777
No.

How does a plan work?

It's that whole airmovement over/under a curved surface that generates lift. we don't have that here. so no.

while that is true.

The trouble is that a jet provides the power and NOT the wheels. So while the wheels may be spinning like crazy the plane will still move.

What the belt, ground, wheels are doing really has no impact on the thrust of the engines. Its still going to have airspeed.

 

[bctbct]

Originally posted by: mugs

Originally posted by: bctbct
No way the plane takes off. The conveyor keeps the plane from gaining forward motion...thus no air forms under the wing to cause lift.

I do have another question though.

A 85 yo guy told me once that he landed a plane flying backwards. He was a pilot in WWII, he said that he was landing a plane in a ninety mph head wind(someplace like Iceland or something) anyway since the headwind was faster than the landing speed, he considered it backwards. Thoughts?

Well... if his AIRSPEED was less than 90mph and the headwind was 90mph, then I guess the plane would have been moving backward. But where the hell was he landing, in a hurricane?

No, he described it as gusting winds, I was just listening to an old guy telling a story so I didnt pay much attention at the time, however after I began to think about it, I do think it is possible because of gravity.

After rereading the exact conditons of the OP I will change my answer to yes. If the conveyor speed increased higher than the thrust of the engine, meaning the plane stayed staionary as I first interpreted, I would say no. But it appears I misunderstood the equation.

 

[Rubycon]

The person on a treadmill analogy is poor. As stated many times over the wheels on a plane do not provide a moving force like a car. Saying a plane would not take off if sitting on a conveyor arranged like a treadmill is like saying a person running on a treadmill would not get knocked over by a swift kick in the ass from a person standing beside the treadmill. In the latter case they fall on their face and get sent to the end of the belt! :laugh:

 

[giantpinkbunnyhead]

Originally posted by: bctbct


A 85 yo guy told me once that he landed a plane flying backwards. He was a pilot in WWII, he said that he was landing a plane in a ninety mph head wind(someplace like Iceland or something) anyway since the headwind was faster than the landing speed, he considered it backwards. Thoughts?

From a physics perspective, yes... that is possible and could be done... but from a pilots perspective, I'd never want to do it myself... While I could land the plane, I don't think I'd care to taxi it around with that kind of wind. Noooo... way!!

On a related note, we had really high winds here two years ago, and they were mostly blowing the hardest in the wee hours of the night. When I arrived at work early the next day, I noticed that some of our DC-6 aircraft (about 70,000 pounds each) and one of our 727 jets (95,000 pounds) were not in the same place we had left them... The wind had actually generated enough airflow over their wings... even though the planes were parked... that the planes lifted up enough to change direction. We always park them facing east, but they were all rotated about 45 degrees northward. Talk about freaky.

 

[Kung Lau]

As mentioned earlier, you do realize how much money we could save if we could have giant "treadmill" like runways at airports and aircraft carriers, right?

 

[erikistired]

nevermind. i'm starting to jump onto the "it will take off" bandwagon but i'd have to see it actually happen to really believe it. or at least see a plane move forward on a conveyor belt, once that happens i would be more convinced.

 

[ta8689]

Heres the question. IF the belt moves faster to compensate for the wheels going faster, then the plane would need to move in order for the wheels to move, since they are not driven. therefore, this belt is already flawed. it didnt compensate and keep it where it was at. the plane moved foreward. so that means the plane can move foreward faster. the plane will move foreward at 20 mph and the wheels will spin at 40 mph.but it still moves foreward in order to make the belt spin faster because the wheels only go faster if the plane is going foreward. So it will get up to lift off speed and take off. Im a private pilot with instrument rating and working on my commercial. my neighbor is a retired airline pilot and agrees with me. The plane lifts off, think good and hard before you try to say im wrong. Still think im wrong? KEEP THINKING!

Also, those of you idiots tha think a plane flies from the air going over the wing from the prop are morons. The prop can only put air over the inside of the wings and around the fuselage. You need air moving over your whole wing. Get in a cessna or a piper. Sit on the numbers on the runway with the throttle all the way in. the nose goes down, but if it was how you said, then the plane would lift off the ground and you would take off like a harrier. The prop moves you, it doesnt create lift. (well technically it makes lift that pulls it foreward, but im talking about lifting force on the wings)

 

[inveterate]

OF COURSE IT"D ****** TAKE OFF WITH UNLIMITED THRUST... LOOK AT ROCKETS... it depends on where the plane is pointed,, if directly horizontal ,, then No it goes no where, but if any verticle at all,, it'll go up

 

[inveterate]

I don't like u

 

[BUrassler]

Originally posted by: crazySOB297
For the people that don't get it:

It would be moving, remember a plane does not get thrust from it's wheels. the wheels will just move forward at twice the speed of the aircraft. if the plane hits 100mph, and the conveyor velt is going 100mph the other direction, total wheel speed will be 200mph, with air flowing over the wings at 100mph.

But the OP said that the belt moves in reverse at the exact same speed as the wheels are moving forward, not the plane's speed. So that exaple doesnt work.

I still don't understand this.

 

[jagec]

Originally posted by: BUrassler

Originally posted by: crazySOB297
For the people that don't get it:

It would be moving, remember a plane does not get thrust from it's wheels. the wheels will just move forward at twice the speed of the aircraft. if the plane hits 100mph, and the conveyor velt is going 100mph the other direction, total wheel speed will be 200mph, with air flowing over the wings at 100mph.

But the OP said that the belt moves in reverse at the exact same speed as the wheels are moving forward, not the plane's speed. So that exaple doesnt work.

I still don't understand this.

The reason this problem sparks such debate is that the original question implies the plane can be kept stationary by putting it on a conveyor belt. In a real-world situation, no conveyor belt can keep a plane from taking off, assuming it has sufficient runway length to get up to takeoff speed.

Here's another analogy. Let's make a dragstrip, where one side is normal asphalt and the other is a giant conveyor belt. Now, stick a car on the conveyor side, put it in neutral, and release the brakes. Put another car on the other side. One car will accelerate to the end of the dragstrip, just like normal, the other car will rely on the conveyor. But wait...when we turn the conveyor belt on, the car's inertia keeps it (more or less) in one place, with the wheel rolling backwards as the conveyor speeds up! The only way that force is transferred from the belt to the car is through the rolling resistance of the wheels, which is very small; we'd have to apply the brakes to see any significant force transfer. Now set up our dragstrip the same way, except on the conveyor, put a rocket car, and set the conveyor to run backwards...when we turn the conveyor on, the rocket car will once again sit almost perfectly still (only a small amount of force being transferred via rolling resistance), but when we light off the rocket it will shoot forwards, regardless of what the conveyor is doing.

 

[BUrassler]

Originally posted by: jagec

Originally posted by: BUrassler

Originally posted by: crazySOB297
For the people that don't get it:

It would be moving, remember a plane does not get thrust from it's wheels. the wheels will just move forward at twice the speed of the aircraft. if the plane hits 100mph, and the conveyor velt is going 100mph the other direction, total wheel speed will be 200mph, with air flowing over the wings at 100mph.

But the OP said that the belt moves in reverse at the exact same speed as the wheels are moving forward, not the plane's speed. So that exaple doesnt work.

I still don't understand this.

The reason this problem sparks such debate is that the original question implies the plane can be kept stationary by putting it on a conveyor belt. In a real-world situation, no conveyor belt can keep a plane from taking off, assuming it has sufficient runway length to get up to takeoff speed.

Here's another analogy. Let's make a dragstrip, where one side is normal asphalt and the other is a giant conveyor belt. Now, stick a car on the conveyor side, put it in neutral, and release the brakes. Put another car on the other side. One car will accelerate to the end of the dragstrip, just like normal, the other car will rely on the conveyor. But wait...when we turn the conveyor belt on, the car's inertia keeps it (more or less) in one place, with the wheel rolling backwards as the conveyor speeds up! The only way that force is transferred from the belt to the car is through the rolling resistance of the wheels, which is very small; we'd have to apply the brakes to see any significant force transfer. Now set up our dragstrip the same way, except on the conveyor, put a rocket car, and set the conveyor to run backwards...when we turn the conveyor on, the rocket car will once again sit almost perfectly still (only a small amount of force being transferred via rolling resistance), but when we light off the rocket it will shoot forwards, regardless of what the conveyor is doing.

Ok, I do understand those examples. For my own peace of mind though, the OP's question/wording is incorrect then and misleading. Right?

 

[GuitarDaddy]

Your example is extremely screwed. You quote items as constants that are quite impossible.

Wheel speed and belt speed are the same in oposite directions and there is perfect traction between them? This is totally impossible if the thrust is coming from the rear of the plane. The wheel speed would be =Thrust+belt speed.

Yes the plane would take off, the wheels would just be spinning much faster than normal.

 

[inveterate]

i cant' believe people debate this,, they either never took physix OR don't bother reading other's posts,, THIS IS SO SIMPLE.. WTF IS WRONG WITH U PEOPLE. STOP POSTING..

 

[zanieladie]

Try it and find out!

 

[shoRunner]

submit it to mythbusters

 

[jagec]

Originally posted by: inveterate
i cant' believe people debate this,, they either never took physix OR don't bother reading other's posts,, THIS IS SO SIMPLE.. WTF IS WRONG WITH U PEOPLE. STOP POSTING..

Most of the people who got it wrong, didn't do so because they misunderstood physics...they did so because they misinterpreted the question. Also, the question itself conveys a rather poor understanding of control systems.