Physics Brainteaser - input from you smart people

[USMARINE1108]

So the following question was posted on another message board I frequent, and it turned into a 66 page flame war with multiple bans and no answer.

"Imagine a plane is sitting on a massive conveyor belt, as wide and as long as a runway. The conveyer belt is designed to exactly match the speed of the wheels, moving in the opposite direction. Can the plane take off?"

[TransAm12sec]

I don't really view this as a complicated problem, but I'm sure it was said on many other forums, stationary air does not create lift.

"Lift is produced by air passing over the wing of an airplane or over the rotor blades of a helicopter. Lift is the force that overcomes the weight of an aircraft so that it can rise in the air. "

http://www.cavalrypilot.com/fm1-514/Ch1.htm


"BERNOULLI'S PRINCIPLE

Bernoulli, an eighteenth century physicist, discovered that air moving over a surface decreases air pressure on the surface (Figure 1-3). As air speed increases, surface air pressure decreases accordingly. This is directly related to the flight of an aircraft. As an airfoil starts moving through the air, it divides the mass of air molecules at its leading edge. The distance across the curved top surface is greater than that across the relatively flat bottom surface. Air molecules that pass over the top must therefore move faster than those passing under the bottom in order to meet at the same time along the trailing edge. The faster airflow across the top surface creates a low-pressure area above the airfoil. Air pressure below the airfoil is greater than the pressure above it and tends to push the airfoil up into the area of lower pressure. As long as air passes over the airfoil, this condition will exist. It is the difference in pressure that causes lift. When air movement is fast enough over a wing or rotor blade, the lift produced matches the weight of the airfoil and its attached parts. This lift is able to support the entire aircraft. As airspeed across the wing or rotor increases further, the lift exceeds the weight of the aircraft and the aircraft rises. Not all of the air met by an airfoil is used in lift. Some of it creates resistance, or drag, that hinders forward motion. Lift and drag increase and decrease together. They are therefore affected by the airfoil's angle of attack into the air, the speed of airflow, the air density, and the shape of the airfoil or wing."

http://www.cavalrypilot.com/fm1-514/IMG00009.GIF

Now, it is assumed that the propeller or jet is not producing the air velocity across the wing needed to lift the plane.

[lilws6]

first thing i thought was yes but i re read it the belt is keeping the plane still so no it won't fly unless there is moving air from someplace else

[Brandon W.]

No you will not..the movement of the tires has no affect..you need air movement to create lift under the wings.

[lilws6]

3-0 in favor of no fly

[lasttimearound]

no it wont fly so make that 4-0 no fly

[lasttimearound]

its kinda like the whole is a fly flying around in your car doing 75mph flying faster than 75mph if he flies from the rear to the front. obviously not

[lilws6]

uhh yea a fly ain't gana do 75 mph lol

[USMARINE1108]

Yes, it will fly. The thrust generated by the engines (doesn't matter if it's a prop or jet) will push the AIRFRAME down the runway. This has nothing to do with the wheels. The thing to remember here is that the thrust is on the airframe, not the wheels. The wheels will always be playing "catch up". Air will still flow over the wings and create lift. The wheels have no effect on the propultion of the aircraft. The wheels will be spinning 2x faster then they would on a runway when the aircraft takes off.

[lasttimearound]

its a treadmill effect, there will be no forward motion, you need airspeed to create lift, if there is no forward motion, there is no lift. you dont feel a breeze while running on a treadmill do you? cars dont (*normally*) jump off of a dyno do they? the force of gravity will keep the wheels on the ground.

[badass88gt]

Yes, it will fly. The thrust generated by the engines (doesn't matter if it's a prop or jet) will push the AIRFRAME down the runway. This has nothing to do with the wheels. The thing to remember here is that the thrust is on the airframe, not the wheels. The wheels will always be playing "catch up". Air will still flow over the wings and create lift. The wheels have no effect on the propultion of the aircraft. The wheels will be spinning 2x faster then they would on a runway when the aircraft takes off.

I would agree with this guy.

The wheels will just free spin, right? They're not driven. The treadmill would just spin them. Therefore, the jet engine will still move the jet. Why wouldnt it?

We dont feel the breeze on a treadmill because we dont have wheels that will free spin, we're running just to keep up without being thrown backwards.

[lasttimearound]

okay, but as the wheels spin faster the belt is *supposed* to speed up with it, so there will never be any actual forward motion created

[WickedSix]

I think the wording needs revision......

if the treadmill is keeping the plane stationary ie the force acting through the wheels is equal and opposite the thrust created by the engine the plane will not fly.....as stated before it is the pressure differential across the wing that creates lift.....a stationary plane does not have lift

[badass88gt]

But, why wouldnt the thrust move the plane forward? There is no force moving from the front to counteract the thrust.

[lasttimearound]

go grab a match box car and hold it still on a treadmill, your hand will be acting as the *thrust* to counteract the reward force of the treadmill.

[badass88gt]

I think the weight of the plane would be the difference. I dont see why gravity wouldnt hold it in place, with the wheels spinning freely, if the belt were started slowly from a dead stop. If you "snapped" the power to full treadmill power, then I could see it being sent backwards?

This needs to be sent to Mythbusters.

[TransAm12sec]

The thrust generated by the engines (doesn't matter if it's a prop or jet) will push the AIRFRAME down the runway.

When the airframe moves faster than 0 mph, the wheels move faster than 0 mph, therefore the belt will counteract the engines thrust. Even though the engine is not driving the wheels, the speed of the wheel matches the speed of the airframe while the tires are on the conveyer belt (with no slippage).

[lasttimearound]

thats what my drunk ass has been trying to say from the begining, but i was trying to put it in simple terms

[USMARINE1108]

When the airframe moves faster than 0 mph, the wheels move faster than 0 mph, therefore the belt will counteract the engines thrust. Even though the engine is not driving the wheels, the speed of the wheel matches the speed of the airframe while the tires are on the conveyer belt (with no slippage).

The belt won't counteract the engines thrust. The wheels spin freely, and the thrust on the airframe will continue to push the aircraft forward as normal. The belt will continue to accelerate in a reverse motion, causing the wheels of the aircraft to move at 2x the speed they normaly do. The forward motion of the aircraft comes from the engines (just like it's flying through the air) and has nothing to do with the speed of the wheels, or movement of the ground.

An aircraft uses the thrust from it's engines to accelerate when it's at 10,000ft just as it will at 0ft. Any effect on the wheels has no effect on the aircraft's acceleration.

[Al]

So...we have a plane here where the wheel speed is double that of the ground speed.

All that matters is that the airspeed is sufficient to get the plane off the ground. The airspeed meter might say 100 knots while the groundspeed indicator will say 200 knots.

It will fly, but I'd be more concerned about the state of the wheels. At what speed will they grenade (remember the concord?)?

[Reverend Cooper]

no,thats like putting a car on the dyno and the roller spining the tires not the tires spinning the roller did the car make power no

[SSDude]

Hmmmm
http://graphics8.nytimes.com/images/2006/12/11/technology/poguespan.jpg

[Moparjim]

Usmarine and Al are correct - it will fly just fine. As stated the thrust from either the jet or prop engines will still move the plane just fine, which will generate lift. Doesn't matter what the wheels are doing they are just freewheeling. The thrust moves the plane, not the wheels. The conveyor moving the other direction has nothing to do with the thrust, which is pushing on the AIR, not the conveyor. The best way I could think of to make you visualize it is this:

Imagine that you are standing on a conveyor bridge and trying to walk across it, and the conveyor is speeding up to match the speed of your walking legs. No progress, correct. That's because your legs (wheels) are providing the motive power. Now imagine that you have a rope above your head that you can hang from and go hand over hand across the same conveyor. Doesn't matter how crazy your legs would be trying to work, your hand over hand motive power would still pull you across while your legs and the conveyor spin all they like.

[Larrygto]

Yes, it will fly. The thrust generated by the engines (doesn't matter if it's a prop or jet) will push the AIRFRAME down the runway. This has nothing to do with the wheels. The thing to remember here is that the thrust is on the airframe, not the wheels. The wheels will always be playing "catch up". Air will still flow over the wings and create lift. The wheels have no effect on the propultion of the aircraft. The wheels will be spinning 2x faster then they would on a runway when the aircraft takes off.I concur!

[6forwardgears]

This thread was hilarious when it was posted on the CamaroZ28 forums. The ideas people come up with are priceless :rolf


Usmarine and Al are correct - it will fly just fine. As stated the thrust from either the jet or prop engines will still move the plane just fine, which will generate lift. Doesn't matter what the wheels are doing they are just freewheeling. The thrust moves the plane, not the wheels. The conveyor moving the other direction has nothing to do with the thrust, which is pushing on the AIR, not the conveyor. The best way I could think of to make you visualize it is this:

Imagine that you are standing on a conveyor bridge and trying to walk across it, and the conveyor is speeding up to match the speed of your walking legs. No progress, correct. That's because your legs (wheels) are providing the motive power. Now imagine that you have a rope above your head that you can hang from and go hand over hand across the same conveyor. Doesn't matter how crazy your legs would be trying to work, your hand over hand motive power would still pull you across while your legs and the conveyor spin all they like.

:thumbsup

[HITMAN]

Wings need air flowing over them to create lift. No air, no lift. No lift, no fly.

[fly5150]

The original question says nothing about thrust or not. So both answers are right. The question does not specify if the plane was running. There is no right answer to the question as both answers are right.

[6forwardgears]

The original question says nothing about thrust or not. So both answers are right. The question does not specify if the plane was running. There is no right answer to the question as both answers are right.

Umm, I think we can assume by "can the plane take off?" that the engines are running like they normally would. Everyone understands that a plane is never going to take off without its engines, much less while rolling backwards on a conveyor.

[WickedSix]

The original question says nothing about thrust or not. So both answers are right. The question does not specify if the plane was running. There is no right answer to the question as both answers are right.

thank you....ambiguous question:thumbsup

[pickardracing]

Welcome to 1998.

[Yooformula]

The original question says nothing about thrust or not. So both answers are right. The question does not specify if the plane was running. There is no right answer to the question as both answers are right.

thats why I voted for not.

[Anakonda69]

The original question says nothing about thrust or not. So both answers are right. The question does not specify if the plane was running. There is no right answer to the question as both answers are right.

x3

[fly5150]

Umm, I think we can assume by "can the plane take off?" that the engines are running like they normally would. Everyone understands that a plane is never going to take off without its engines, much less while rolling backwards on a conveyor.

Can't assume. When you assume you make an a$$ out of you and me.
:thumbsup

[xxsn0blindxx]

I don't really view this as a complicated problem, but I'm sure it was said on many other forums, stationary air does not create lift.

"Lift is produced by air passing over the wing of an airplane or over the rotor blades of a helicopter. Lift is the force that overcomes the weight of an aircraft so that it can rise in the air. "

http://www.cavalrypilot.com/fm1-514/Ch1.htm


"BERNOULLI'S PRINCIPLE

Bernoulli, an eighteenth century physicist, discovered that air moving over a surface decreases air pressure on the surface (Figure 1-3). As air speed increases, surface air pressure decreases accordingly. This is directly related to the flight of an aircraft. As an airfoil starts moving through the air, it divides the mass of air molecules at its leading edge. The distance across the curved top surface is greater than that across the relatively flat bottom surface. Air molecules that pass over the top must therefore move faster than those passing under the bottom in order to meet at the same time along the trailing edge. The faster airflow across the top surface creates a low-pressure area above the airfoil. Air pressure below the airfoil is greater than the pressure above it and tends to push the airfoil up into the area of lower pressure. As long as air passes over the airfoil, this condition will exist. It is the difference in pressure that causes lift. When air movement is fast enough over a wing or rotor blade, the lift produced matches the weight of the airfoil and its attached parts. This lift is able to support the entire aircraft. As airspeed across the wing or rotor increases further, the lift exceeds the weight of the aircraft and the aircraft rises. Not all of the air met by an airfoil is used in lift. Some of it creates resistance, or drag, that hinders forward motion. Lift and drag increase and decrease together. They are therefore affected by the airfoil's angle of attack into the air, the speed of airflow, the air density, and the shape of the airfoil or wing."

http://www.cavalrypilot.com/fm1-514/IMG00009.GIF

Now, it is assumed that the propeller or jet is not producing the air velocity across the wing needed to lift the plane.


WINNER! /thread

If the plane is not moving relative to earth's surface there is no air movement along the wings meaning no lift. In other words tha plane is not pushing against the air molecules to generate lift. I've seen some argue that the thrust of the jets will provide air movement, however, the thrust of the jets would not provide sufficient air movement to create enough lift for the plane to fly. If the plane was tied so that it could not move backwards and the engines were off it certainly would not take off, having the engines on and nothing tied to the plane is equivalent.

[lasttimearound]

the whole thrust is on the airframe doesnt make a difference, look at a jet car, the wheels spin as a result of the forward motion on the frame of the, the wheels spin at the same rate of travel as the rest of the car, look at a plane, the whole idea is that the wheels keep up with the speed of the plane thats what keeps them from wearing out or flat spotting then blowing up

[Al]

Wings need air flowing over them to create lift. No air, no lift. No lift, no fly.

Think airspeed, not groundspeed.


Hey fly5150, what do you fly?

[lasttimearound]

right, airspeed, if your not making forward motion, how are you going to get airspeed?

[6forwardgears]

right, airspeed, if your not making forward motion, how are you going to get airspeed?

Right, but the real question is, are you going to be moving forward or not? You will, since all the wheels are doing is rolling. There is a *tiny* amount of rolling resistance that they'll be exerting against the thrust from the plane's engines, but it is obviously not enough to keep it from moving.

[badass88gt]

Could a guy test the whole thing with an R/C Plane and a treadmill? Smaller scale obviously, but should prove or disprove, wouldnt it?

[Yooformula]

with enough thrust it would fly just like a rocket does but a traditional plane wouldnt make enough thrust would it? I would think that a prop plane would create more lift for the wings as air is forced over the top/bottom of the wings than an engine on a normal plane without propellers.

[Yooformula]

Could a guy test the whole thing with an R/C Plane and a treadmill? Smaller scale obviously, but should prove or disprove, wouldnt it?

an r/c plane with propellers can take off almost instantly because it creates lift from a standstill but a thrusted plane does not. It pushes the plane creating lift through speed.
is there an official answer to this or what?

[fireguyrick]

Well, in theory, would not the tarmac of a runway already be moving due to planatary rotation? The plane can take off with this rotation.

Rick

[lasttimearound]

no, the spinning doesnt create wind. there is a reason airports have planes land and take off into the wind. or carriers turn into the wind and try to speed up while launching (or at least used to)

[pickardracing]

Somebody call Adam and Jamie.

[janna_camaro]

Is this smarter than 5th grader here..Come on this is easy no air over the wings its a rock. I don't think we need usless pirctures and novels on this. In the example there is no mention of thrust from the aircraft

[USMARINE1108]

The original question says nothing about thrust or not. So both answers are right. The question does not specify if the plane was running. There is no right answer to the question as both answers are right.

It also says nothing about the aircraft having any wings, about the aircraft being chained to the ground, or that there is even a pilot in the cockpit to advance the throttles so the aircraft will ever fly. By your logic, you can assume anything. The question could be as complicated as you want it to be.

The way I see it, when it asks if the aircraft will take off, it is telling you that it has the ability to take off on a normal runway under normal conditions.

[lasttimearound]

thats how im looking at it too.

[janna_camaro]

It also says nothing about the aircraft having any wings, about the aircraft being chained to the ground, or that there is even a pilot in the cockpit to advance the throttles so the aircraft will ever fly. By your logic, you can assume anything. The question could be as complicated as you want it to be.

The way I see it, when it asks if the aircraft will take off, it is telling you that it has the ability to take off on a normal runway under normal conditions.

Yes has the ability ...it has wings because it says its an aircraft and aircraft have wings. It says its on a runnway, it could be remote control.

[badass88gt]

I think you guys are looking at way too many things to prove or disprove it. Obviously the question is intended as a fully functional aircraft. Who the hell would even think that its just a Boeing "roller"?

[Moparjim]

WINNER! /thread

If the plane is not moving relative to earth's surface there is no air movement along the wings meaning no lift. In other words tha plane is not pushing against the air molecules to generate lift. I've seen some argue that the thrust of the jets will provide air movement, however, the thrust of the jets would not provide sufficient air movement to create enough lift for the plane to fly. If the plane was tied so that it could not move backwards and the engines were off it certainly would not take off, having the engines on and nothing tied to the plane is equivalent.

The thrust from the engines does indeed move the plane relative to the EARTH. Again, doesn't matter what the conveyor is doing... Hence, it flys...

[Teufelhunden]

http://www.kottke.org/06/02/plane-conveyor-belt

[Moparjim]

Is this smarter than 5th grader here..Come on this is easy no air over the wings its a rock. I don't think we need usless pirctures and novels on this. In the example there is no mention of thrust from the aircraft

For the millionth time there is airflow over the wings, the plane moves relative to the earth driven by the jet or prop THRUST acting on the air. The conveyor and freerolling wheels doesn't make a bit of difference either way.

P.S. Its an engineering degree from M.S.O.E., not the 5th grade, thanks.

[Moparjim]

Also, there is no specific mention of thrust but there is mention of an AIRPLANE which means there is thrust be it by jet, prop, or frikken rocket power. It doesn't mention a GLIDER sitting on the conveyor which would just be a retarded question. So... one more time... Whatever is propelling the airplane produces THRUST behind it to propel it forward. The wheels are just freewheels so the thing doesn't drag across the ground. Doesn't matter what the conveyor under it does, the wheels will just spin freely. The thrust of the prop or jet or rocket acting on the air is what moves the plane relative to the EARTH which creates the lift under the wings. Again, since the word AIRPLANE is used, it has wings, or some type of lift creating airfoil that can be considered the equivalent.

[badass88gt]

Think about this: Put a tire on a tread mill that is moving. Pushing the tire up the treadmill is hard because you are driving the tire with your arms by pushing it. Now take a wheel with an axle thru it so the wheel freely rotates on the axle. Push the axle with your arms and the tire will go right up the tread mill.

[HRSEPLA]

Side note:
So what does a big plane run in the 1/4 mile?
And What is a normal top speed when it takes off?

[Moparjim]

Side note:
So what does a big plane run in the 1/4 mile?
And What is a normal top speed when it takes off?

No idea on a big plane, but I recall the F16 vrs Viper shootout a few years back and I think the Viper was faster to 100 MPH before being smoked by the jet so I would guess a jet fighter would run a 10/11 second 1/4 mile, enough to get on the bottom rungs of the ladder lol.

Stall or takeoff speed for planes varies highly depending on the plane size, weight, and propulsion, I think most jets it is 150 MPH or so but I would have to look it up.

[Moparjim]

Looked it up, from the interweb takeoff speed of a 727:

"The takeoff and landing speeds vary not only from airplane to airplane, but are also affected by factors such as aircraft weight, airport elevation and outside air temperature (which affect air density). For each takeoff and landing, calculations are made by the pilots to figure the correct speeds.

Some airplanes have onboard computers which display the correct speeds after the pilots enter some basic figures. On other airplanes, a simple "flip chart" or graph is used by the pilots to figure the correct speeds to use.

If I had to choose an average speed, though, I'd say it's around 130-140 knots for takeoff (around 140-152 statute miles per hour) for takeoff, and around 10 knots (or miles per hour) less for landing. It can actually vary quite a bit, however, and if you ask another pilot's opinion you may get a somewhat different answer, but it would likely be in this range. (By the way, a handy, if inexact, way to convert knots to miles per hour is to add 15%. For instance, 100 knots is approximately 115 miles per hour.)"

My guess was right on the money...

[USMARINE1108]

For the millionth time there is airflow over the wings, the plane moves relative to the earth driven by the jet or prop THRUST acting on the air. The conveyor and freerolling wheels doesn't make a bit of difference either way.

P.S. Its an engineering degree from M.S.O.E., not the 5th grade, thanks.

That's the thing here. Most people seem to be getting caught up in the idea that the belt will keep the airplane in the same place relative to the ground. That simply is not the case.

Thrust on the airframe moves the airframe forward in relation to the stable earth, just as it does at any altitude. As the aircraft moves forward, air flows over the wings and lift is generated just like a normal take off. As the belt moves under the wheels, the wheels just spin faster. The belt moving has NOTHING to do with the airframe accelerating. That's what happened on the other board too. Funny, the poll results came out to be about what they are now, with the "won't fly" staying just a little ahead of the "will fly". That's with over 1000 votes, too.

[Cjburn]

I really don't consider this crap a brainteaser. What it really does is make people see past the point of the moving conveyor belt, since it has absolutely no bearing on whether or not the plane would attain forward motion. It would, however move forward, since the movement of the plane (itself) is no way linked to which the speed of the wheels (they are "free"). The plane would eventually reach the speed it would need take off, and simply fly.

[Yellow2k1vette]

The plane will fly...but both wheel speed and conveyor speed will be zero when it occurs.

The plane's tires will skid until it lifts off.

:haveabeer

[Lash]

It will take off. there is a 1,000 page thread on clubgp about this same topic....lol. Somebody actually made a gif about this to fully explain it better....LMAO.

[USMARINE1108]

The plane will fly...but both wheel speed and conveyor speed will be zero when it occurs.

The plane's tires will skid until it lifts off.

:haveabeer

The belt moves in the opposite direction, so the wheels would move at 2x the speed of the aircraft. But you're right, either way, the plane would fly.

[USMARINE1108]

It will take off. there is a 1,000 page thread on clubgp about this same topic....lol. Somebody actually made a gif about this to fully explain it better....LMAO.

Hahaha, I had no idea this was such a popular topic. The other board I saw it on was the first time I've heard of it.

[70challenger452]

it's already been said but it will take off, the only deal with the convayer belt is it makes the wheels turn twice as fast and the wheels have nothing to do with forward movment, it might just make the take off just a little longer from the increased friction with the wheels moving twice as fast

[70challenger452]

Somebody call Adam and Jamie.

I saw jamie in san fran last thursday, I was kinda weird seeing someone you only see on tv

[Lash]

Hahaha, I had no idea this was such a popular topic. The other board I saw it on was the first time I've heard of it.


Yeah......it was about 6 months ago or so. The thread was ginormous.

[Reverend Cooper]

no way i wanna see it proven for real the plane has no forward movement,thus no air flow over the wings, if the plane is stationary and only the conveyor and wheels move where is the air flow coming from over the wings to create the lift

[Berettaspeed]

i always thought the wings is what flew the plane because of lift. i wonder why the wheels get tucked into the plan. hope it doesn't fall the the gear is up. LOL

plane will not fly. unless the belt will create air movement strong enough to create lift. it has nothing to do with the wheels.

[Silver03SRT]

hmmmm let me think about this one some more,

[Syclone0044]

I think the subtle catch is that even though the conveyor speed matches the opposite of the aircraft's land speed, the aircraft still manages to move forward along the conveyor, it's just that as the aircraft moves down the conveyor runway, its wheel speed will increase with distance at a higher rate than normal. Fast wheel speed on a moving aircraft doesn't prevent it from flying.

[Al]

BAD ENGRISH!!!

I'd like to mention that the original question is poorly worded.

The same thing applies to the "what is the only thing you can believe without a doubt that a compulsive liar would say?"

Time for the mythbusters.

[TransAm12sec]

One thing that came to my mind was wheel speed being considered as velocity, not angular speed.

With the idea of the wheels spinning freely (no friction on the hub/wheel bearing); if the thrust = 0, and the conveyer belt is turned on, the plane would remain in the same position given no friction.

"If the brakes were locked, then sure, the friction between the tires and the treadmill would be a factor to consider. However, we only need to concern ourselves with the friction in the wheel bearings, which is negligible."

"You're right, the airplane will move forward. Unlike a wheel-driven automobile, aircraft propulsion relies on Newton's Third Law. Thus, when the airplane starts pumping air backward, if the wheels have any reasonable freedom of rotation the plane _will_ move forward regardless of what the damn conveyor is doing.
Given this, the really interesting part of this problem lies in how the conveyor belt's control is programmed. "The conveyer belt is designed to exactly match the speed of the wheels, moving in the opposite direction." If this is taken literally one could argue that, since the wheels start at zero RPM and are not being forced to turn, the conveyor should hold the wheels at zero regardless of the plane's motion (-0 = 0). Thus, the conveyor would follow the plane's motion, and the plane would take off with the wheels at rest.

We could also interpret this as having the conveyor oppose the wheel rotation caused by the airplane's motion as if it were on a runway, in which case the plane would lift off with the wheels spinning at -2X their normal rate. Blown tires and an aborted takeoff are likely.

Or, we could interpret it as the author would mislead us into thinking, that the conveyor should move opposite the plane's attempted motion at a rate sufficient to keep it in place. Since the conveyor cannot prevent that motion, in theory its backward speed will quickly go to infinity. At which point the plane may fly through a wormhole to its destination, saving much time and fuel. Or a black hole will form that ingests plane, conveyor, and eventually Earth. I look forward to the experiment. I think."

http://www.boingboing.net/2006/12/11/airplanetreadmill_pr.html

The easiest way I understand it is the friction of the wheel bearings is negligible.

[Heat Seeker WS6]

I don't really view this as a complicated problem, but I'm sure it was said on many other forums, stationary air does not create lift.

"Lift is produced by air passing over the wing of an airplane or over the rotor blades of a helicopter. Lift is the force that overcomes the weight of an aircraft so that it can rise in the air. "

http://www.cavalrypilot.com/fm1-514/Ch1.htm


"BERNOULLI'S PRINCIPLE

Bernoulli, an eighteenth century physicist, discovered that air moving over a surface decreases air pressure on the surface (Figure 1-3). As air speed increases, surface air pressure decreases accordingly. This is directly related to the flight of an aircraft. As an airfoil starts moving through the air, it divides the mass of air molecules at its leading edge. The distance across the curved top surface is greater than that across the relatively flat bottom surface. Air molecules that pass over the top must therefore move faster than those passing under the bottom in order to meet at the same time along the trailing edge. The faster airflow across the top surface creates a low-pressure area above the airfoil. Air pressure below the airfoil is greater than the pressure above it and tends to push the airfoil up into the area of lower pressure. As long as air passes over the airfoil, this condition will exist. It is the difference in pressure that causes lift. When air movement is fast enough over a wing or rotor blade, the lift produced matches the weight of the airfoil and its attached parts. This lift is able to support the entire aircraft. As airspeed across the wing or rotor increases further, the lift exceeds the weight of the aircraft and the aircraft rises. Not all of the air met by an airfoil is used in lift. Some of it creates resistance, or drag, that hinders forward motion. Lift and drag increase and decrease together. They are therefore affected by the airfoil's angle of attack into the air, the speed of airflow, the air density, and the shape of the airfoil or wing."

http://www.cavalrypilot.com/fm1-514/IMG00009.GIF

Now, it is assumed that the propeller or jet is not producing the air velocity across the wing needed to lift the plane.

:wstupid
Exactly. Air speed relative to the wing is what causes lift.

[HITMAN]

I don't care what your degree is in, the question states that the AIRcraft's forward speed is matched by conveyor belt moving underneath it, which to me means that even if the plane's theoretical speed is 1000mph, it still remains stationary in it's own space. No flow on the wings. No lift is generated. No flight is achieved. ThrustSSC accelerated to 763 mph. It didn't achieve flight. No wings. If you ran it up a ramp at that speed, inertia would let it fly for a while, but without wings, eventually it would fall out of the sky even at that great speed.

Now, if the engines (propeller style or jet) were mounted in front of the wings (the original question never states the type of construction) and could generate enough airflow over the wings to create the necessary lift needed for flight without destroying the wings surface due to excess heat (jet exhaust), then the answer to the question is yes. But, this was never specified.

[Moparjim]

I don't care what your degree is in, the question states that the AIRcraft's forward speed is matched by conveyor belt moving underneath it, which to me means that even if the plane's theoretical speed is 1000mph, it still remains stationary in it's own space. No flow on the wings. No lift is generated. No flight is achieved. ThrustSSC accelerated to 763 mph. It didn't achieve flight. No wings. If you ran it up a ramp at that speed, inertia would let it fly for a while, but without wings, eventually it would fall out of the sky even at that great speed.

Now, if the engines (propeller style or jet) were mounted in front of the wings (the original question never states the type of construction) and could generate enough airflow over the wings to create the necessary lift needed for flight without destroying the wings surface due to excess heat (jet exhaust), then the answer to the question is yes. But, this was never specified.

For the millionth time - the plane moves, lift is created. Does not matter what the conveyor does, since the wheels are NOT what propels the airplane forward. All of you that think the plane won't fly are simply not looking at it properly. If it were a car, sure the car wouldn't move because the wheels of the car are what propels it forward - the wheels putting power to the ground. In a PLANE, the prop or jet or rocket acts on the AIR to push the plane forward so it will indeed move forward just fine in relation to the earth even though the conveyor is spinning away backwards. Same reason a plane can take off from ice, snow, water, etc. (with skis or floats or whatever obviously). It doesn't need to drive off of the ground (or in this case conveyor) to move forward.

I am truly amazed that apparently more 50% or more of the population is apparently DENSE in this matter. It apparently is an inherently ingrained way of thinking about this that most people have developed, a paradigm so to speak, that prevents a lot of people from looking at it properly. The key point most of the naysayers do not seem to understand is that they think the plane will not move because of the conveyor, thus it will not generate lift. This is just WRONG, as myself and others have tried to explain.

[Moparjim]

Yet another visual for you:

Go home and put some roller skates on, and get on your treadmill in the basement. Turn treadmill on, as slow or as fast as you want. If you try to SKATE up the treadmill, or if the skate wheels were powering you, obviously you cannot move. However, if you simply grab the side rails and use your arms, you can pull yourself forward all you want, using your arms providing motive force against the siderails and your skates just freewheeling - no matter how fast the treadmill is going, your wheels will just spin faster. This is how the plane works - the jet or prop or rocket power provides the motive force to move the plane by pushing on the air which is totally independant of the conveyor below it. In the treadmill example, if you strapped a rocket, jet, big enough fan or anything else that provided thrust to your ass you would move as well, no matter how fast the treadmill was going the opposite direction.

[HRSEPLA]

No idea on a big plane, but I recall the F16 vrs Viper shootout a few years back and I think the Viper was faster to 100 MPH before being smoked by the jet so I would guess a jet fighter would run a 10/11 second 1/4 mile, enough to get on the bottom rungs of the ladder lol.

Stall or takeoff speed for planes varies highly depending on the plane size, weight, and propulsion, I think most jets it is 150 MPH or so but I would have to look it up.


Thanks Jimmy!
You just got bumped by a 747 beoch:rolf

[6forwardgears]

For the millionth time - the plane moves, lift is created. Does not matter what the conveyor does, since the wheels are NOT what propels the airplane forward. All of you that think the plane won't fly are simply not looking at it properly. If it were a car, sure the car wouldn't move because the wheels of the car are what propels it forward - the wheels putting power to the ground. In a PLANE, the prop or jet or rocket acts on the AIR to push the plane forward so it will indeed move forward just fine in relation to the earth even though the conveyor is spinning away backwards. Same reason a plane can take off from ice, snow, water, etc. (with skis or floats or whatever obviously). It doesn't need to drive off of the ground (or in this case conveyor) to move forward.

I am truly amazed that apparently more 50% or more of the population is apparently DENSE in this matter. It apparently is an inherently ingrained way of thinking about this that most people have developed, a paradigm so to speak, that prevents a lot of people from looking at it properly. The key point most of the naysayers do not seem to understand is that they think the plane will not move because of the conveyor, thus it will not generate lift. This is just WRONG, as myself and others have tried to explain.

Thanks Jim, you took every last word right out of my mouth :headbang