interesting argument.. (for the self proclaimed geniuses of IA)

[tony]

Saw this on Supraforums and it was a pretty interesting read.

A plane (747 passenger jet) is sitting on a runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the planes speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).

The question is:

Will the plane (747 passenger jet) take off or not?

[Ruiner]

Yes. The wheels on the plane will only offer a limited amount of drag via the conveyor belt. Once the drag is eliminated via forward thrust, the plane will begin to move forward and will eventually take off (if given enough thrust). The conveyor will hardly play a part.

[/thread]

[Spyder]

Yes. The wheels on the plane will only offer a limited amount of drag via the conveyor belt. Once the drag is eliminated via forward thrust, the plane will begin to move forward and will eventually take off (if given enough thrust). The conveyor will hardly play a part.

[/thread]
This has been discussed before, and several people had different awnsers. The real question that came up in another thread was, how can a plane "take off" with no air under its wings?

[Ruiner]

This has been discussed before, and several people had different awnsers. The real question that came up in another thread was, how can a plane "take off" with no air under its wings?

I said that it had to "move forward" with an appropriate thrust. Read my answer again. Air has to be moving over/under the wings. What I am saying is that NO conveyor belt will hold a plane in one position once the plane's thrust overtakes the drag on the wheels. [/thread]

[Spyder]

I said that it had to "move forward" with an appropriate thrust. Read my answer again. Air has to be moving over/under the wings. What I am saying is that NO conveyor belt will hold a plane in one position once the plane's thrust overtakes the drag on the wheels. [/thread]
The reason this is being argued is because in the described scenero the belt accelerates at EXACTLY the same speed as the plane, there for the plane in essence stays still.

EDIT: I read exactly what you wrote, the problem with it is , it doesnt have anything to do with the question.

[man]

The plane would lift off as normal.

/thread... again

[Ruiner]

The reason this is being argued is because in the described scenero the belt accelerates at EXACTLY the same speed as the plane, there for the plane in essence stays still.

EDIT: I read exactly what you wrote, the problem with it is , it doesnt have anything to do with the question.

I don't care if the belt is running at 1 million miles per hour. It will only put a certain amount of drag on the wheels, bearings, etc. A plane's engine thrust can easily overcome that drag and move forward.

Hold a match-box car on a treadmill. Put the treadmill on slow, medium, and fast speeds. Push the car forward while the treadmill is at each speed. 100 to 1 you will use the same force each time to push the car foward. That force is enough to overcome the drag on the wheels. If the treadmill is moving at 200 mph in reverse, you would still only need a certain amount of force to push it forward.

The plane would take off...

[chrisdavis]

This has been discussed before, and several people had different awnsers. The real question that came up in another thread was, how can a plane "take off" with no air under its wings?


LOL I was just thinking that as I was reading it.

[man]

I don't care if the belt is running at 1 million miles per hour. It will only put a certain amount of drag on the wheels, bearings, etc. A plane's engine thrust can easily overcome that drag and move forward.

Hold a match-box car on a treadmill. Put the treadmill on slow, medium, and fast speeds. Push the car forward while the treadmill is at each speed. 100 to 1 you will use the same force each time to push the car foward. That force is enough to overcome the drag on the wheels. If the treadmill is moving at 200 mph in reverse, you would still only need a certain amount of force to push it forward.

The plane would take off...

Edzachary, the plane would not move if it was propelled by its wheels, also, you have to remember if the plane isn't physically moving, it's speedo will read 0 because it is measured by airspeed, so the belt wouldn't move either.

[chrisdavis]

I don't care if the belt is running at 1 million miles per hour. It will only put a certain amount of drag on the wheels, bearings, etc. A plane's engine thrust can easily overcome that drag and move forward.

Hold a match-box car on a treadmill. Put the treadmill on slow, medium, and fast speeds. Push the car forward while the treadmill is at each speed. 100 to 1 you will use the same force each time to push the car foward. That force is enough to overcome the drag on the wheels. If the treadmill is moving at 200 mph in reverse, you would still only need a certain amount of force to push it forward.

The plane would take off...

I think that in essence the question is could you make the plane take off at a stand still. Which is no, you even stated the plane has to move forward.

[man]

I think that in essence the question is could you make the plane take off at a stand still. Which is no, you even stated the plane has to move forward.

I don't think it is though, seems too easy.

[Spyder]

I don't care if the belt is running at 1 million miles per hour. It will only put a certain amount of drag on the wheels, bearings, etc. A plane's engine thrust can easily overcome that drag and move forward.

Hold a match-box car on a treadmill. Put the treadmill on slow, medium, and fast speeds. Push the car forward while the treadmill is at each speed. 100 to 1 you will use the same force each time to push the car foward. That force is enough to overcome the drag on the wheels. If the treadmill is moving at 200 mph in reverse, you would still only need a certain amount of force to push it forward.

The plane would take off...

but, with the example you gave you are causing the match box car to accelerate at a greater rate then the tread mill is turning... the tread mill would accelerate at exactly the same speed as the car was being pushed, hence effectively keeping the car still. the faster you push the faster the tread mill moves in reverse.

[Spyder]

I think that in essence the question is could you make the plane take off at a stand still. Which is no, you even stated the plane has to move forward.

exactly.

if 2 forces are equal and opposite they cancel each other out.

[man]

exactly.

if 2 forces are equal and opposite they cancel each other out.
but the forces arent equal

[Speedm0(\)key]

dude.. i've been here thinking this thru for 10 minutes... and i came to following conclusion:




lets find tony and beat him senseless

[Spyder]

but the forces arent equal
explain how and i will agree, that is the only basis for my argument.

[man]

dude.. i've been here thinking this thru for 10 minutes... and i came to following conclusion:




lets find tony and beat him senseless

Good Idea!!!

P.S. Mine and Ruiners conclusions are correct.

[Spyder]

dude.. i've been here thinking this thru for 10 minutes... and i came to following conclusion:




lets find tony and beat him senseless

Actually i take back what i said, this is the correct awnser. :D

[Tiff-O-Bitties]

but the wheels do not push the plane.. they simply guide it.. I think it would still take off but then again.. I'm really no genius..

[man]

explain how and i will agree, that is the only basis for my argument.

There are many more factors here than just the speed of the belt compared to the speed of the wheels on the plane: friction, thrust, weight. They all factor in. Also planes measure speed by how fast the air is moving, so the plane would have to physically move in order for the belt to start moving. Once the plane is moving, the friction on the tires is close to nothing compared to the thrust from the jet engine. The matchbox car example is a perfect example, the wheels on the plane will always be able to match that of the belt, and, in the matchbox situation, the hand pushes the car forward, much like a jet engine.

but the wheels do not push the plane.. they simply guide it.. I think it would still take off but then again.. I'm really no genius..
Exactly!!!

[Speedm0(\)key]

but the wheels do not push the plane.. they simply guide it.. I think it would still take off but then again.. I'm really no genius..

i think all women shouldnt be allowed to answer or even attempt to answer tony's question.

[Spyder]

Good Idea!!!

P.S. Mine and Ruiners conclusions are correct.
Prove it, i have always wondered.

[Speedm0(\)key]

Actually i take back what i said, this is the correct awnser. :D:look:

[man]

i think all women shouldnt be allowed to answer or even attempt to answer tony's question.
Actually she is correct to an extent.

[Speedm0(\)key]

Actually she is correct to an extent.


dude... thanks for fucking that up.

let me introduce myself: im speedmonkey .. im an asshole wether you're right or wrong.

[Kevykev]

Ok if the the conveyor belt is moving directionally against the plane AT THE SAME SPEED, THE PLANE WILL BE STILL.

[Speedm0(\)key]

ok now seriously, the plane needs AIR to travel against it to take off... like this: (wind)---><----(plane) with out this IT CAN NOT TAKE OFF

[Kevykev]

Let's call those guys at "myth busters."

[Calvin200sx]

The plane will never take off. If the conveyor is moving in the opposite direction as the forward motion of the plane, the plane is essentially standing still. If there is no air movement over the wings, there is no lift. A plane will not lift off without airflow. The jets only act to push the plane forward fast enough through the air to generate enough lift to get the plane off the ground. Prop planes opperate under the same guidelines only the prop pushes/pulls the plane through the air to generate lift on the wings. So no airflow (forward motion) no flying.

[Speedm0(\)key]

The plane will never take off. If the conveyor is moving in the opposite direction as the forward motion of the plane, the plane is essentially standing still. If there is no air movement over the wings, there is no lift. A plane will not lift off without airflow. The jets only act to push the plane forward fast enough through the air to generate enough lift to get the plane off the ground. Prop planes opperate under the same guidelines only the prop pushes/pulls the plane through the air to generate lift on the wings. So no airflow (forward motion) no flying.


i already said this. but +1

[tony]

Just to throw a monkey wrench in this, for the plane to take off it requires thrust correct? If the belt compensates for the speed of the PLANE and not the WHEELS (this is all hypothetical) then how is the plane able to take off and where is the thrust coming from? I'm not saying you guys are right or wrong but the answer isnt as simple as "yes it will take off" or "the wheels arent driving the plane" we know that.. the belt speeds up with the speed of the plane so in essence the plane is going nowhere.

[Speedm0(\)key]

Just to throw a monkey wrench in this, for the plane to take off it requires thrust correct? If the belt compensates for the speed of the PLANE and not the WHEELS (this is all hypothetical) then how is the plane able to take off and where is the thrust coming from? I'm not saying you guys are right or wrong but the answer isnt as simple as "yes it will take off" or "the wheels arent driving the plane" we know that.. the belt speeds up with the speed of the plane so in essence the plane is going nowhere.


you're gonna get jumped for asking that gay question tony, my head hurts

[man]

ahhh.... I guess you guys should start designing planes now, apparently all of my aerospace engineering professors have been teaching me the wrong stuff!!!

Oh and I have a REAL solution:
Sell the 747, buy a Harrier

[Speedm0(\)key]

ahhh.... I guess you guys should start designing planes now, apparently all of my aerospace engineering professors have been teaching my the wrong stuff!!!

Oh and I have a REAL solution:
Sell the 747, buy a Harrier


plus +0.5 <-- would give you a 1, but.. im gonna start being a jew with points because.. well there really isnt a reason

[man]

thanks, lol

[chrisdavis]

ahhh.... I guess you guys should start designing planes now, apparently all of my aerospace engineering professors have been teaching my the wrong stuff!!!

I understand what you and Ruiner are saying. In a real world environment the plane would take off. But the question posed is "Can a 747 take off without leaving its stationary position?" which by both of your accounts is no. The plane must move forward. The question confuses by placing emphasis on the wheels to the conveyor as if the wheels are the driving mechanism.

[B16a2 Civic]

the biggest question is....does the plane have gas?

[tony]

ahhh.... I guess you guys should start designing planes now, apparently all of my aerospace engineering professors have been teaching me the wrong stuff!!!

Oh and I have a REAL solution:
Sell the 747, buy a Harrier


your signature alone makes you right.. lol Actually you and ruiner are right from what I've seen, I just wanted a big 10 page argument about why it couldn't take off.

[man]

the question posed is "Can a 747 take off without leaving its stationary position?" which by both of your accounts is no. The plane must move forward. The question confuses by placing emphasis on the wheels to the conveyor as if the wheels are the driving mechanism.
But it never states that, I think the answer depends on the way you interpret it. Which is its goal, to create argument by interpretation.

[Tiff-O-Bitties]

the biggest question is....does the plane have gas?

bwahaha

[Ruiner]

but, with the example you gave you are causing the match box car to accelerate at a greater rate then the tread mill is turning...


WRONG! The WHEELS are the only drag. Once that drag is broken, the car moves forward.

[Ruiner]

explain how and i will agree, that is the only basis for my argument.

The WHEELS are the only means of drag. Does that make sense to you? ONLY the wheels. They spin freely.

[Ruiner]

Ok if the the conveyor belt is moving directionally against the plane AT THE SAME SPEED, THE PLANE WILL BE STILL.

No! The wheels are the limiting factor of drag, NOT THE PLANE itself.

[Ruiner]

Just to throw a monkey wrench in this, for the plane to take off it requires thrust correct? If the belt compensates for the speed of the PLANE and not the WHEELS (this is all hypothetical) then how is the plane able to take off and where is the thrust coming from? I'm not saying you guys are right or wrong but the answer isnt as simple as "yes it will take off" or "the wheels arent driving the plane" we know that.. the belt speeds up with the speed of the plane so in essence the plane is going nowhere.

The problem is that you cannot compensate for the speed of the plane.

However, if the plane has ENOUGH FRICTION/DRAG to keep it in one place, it will never take off. A plane has to have forward motion through the AIR in order to generate lift.

[turbowrx]

Air must pass over and under a planes wing and elevators for "lift off" to occur. If the belt matches the speed no air is produced. If you run on a treadmill no matter how fast you go you wont feel wind pass by your face.

[ISAtlanta300]

I don't think it will take off, just like a car on a dyno does not move forward........

[SilverStoneZ]

Saw this on Supraforums and it was a pretty interesting read.

A plane (747 passenger jet) is sitting on a runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the planes speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).

The question is:

Will the plane (747 passenger jet) take off or not?

the plan will take off here is why useing the match box car example if you push the car at 10mph and the conveyor moves at 10 mph the car will move forward on the conveyor its a complex math problem but there will forward motion by the plane. The reasion you dont more forward on a treadmill is because you actualy stop moveing you let one foot stay planted on the conveyor while you move the other to the front. in the case of the plane this is not so the plane is constantly makeing contact but never stoping due to its thursters so in a sence the plains wheel will be traveling at 2x the speed the plain is causeing the plane to move forward and take off. wow my head hurts now.

Edit: with the treadmill your feet are the driveing force not true with the wheels of the palne

Edit 2: when you HOLD the car in the Treadmill how fast is the car moveing the answer is its not the wheels are and your hand is the moveing force as is with the planes thursters ps i cant spell

[SilverStoneZ]

I don't think it will take off, just like a car on a dyno does not move forward........

yes but with the dyno the Wheel act as the moveing force. no so with a plane

[SilverStoneZ]

the whels on the plane only act only as a surface for the plane to move on

[IndianStig]

Given that the velocity of both the plane and the runaway conveyor are equal in magnitude but opposite in direction. No way in hell its gonna lift off unless its a Harier Jet, but its a 747.

NOw you said moving, which means that the plane moved from one distance, Xi to Xf, so if it is creating enough upforce to trump gravity then yeah we could get there, but i dont think the way you worded it is right for that.

[SilverStoneZ]

it has everything to do with the wheels and them NOT being the driveing force of the plane as Rniner said the wheels spin freely and if the plan is sitting still than the conveyor would not be moveing because the speed of the plane would = zero so for the conveyor to move at all the plane must move forward. The only reasion the plane can take off is because the wheels and driveing force are not directly linked as they are on a car via trans. driveshaft ....

[IndianStig]

it has everything to do with the wheels and them NOT being the driveing force of the plane as Rniner said the wheels spin freely and if the plan is sitting still than the conveyor would not be moveing because the speed of the plane would = zero so for the conveyor to move at all the plane must move forward. The only reasion the plane can take off is because the wheels and driveing force are not directly linked as they are on a car via trans. driveshaft ....

there is no mention of the throttle being on, is there?

[Ruiner]

there is no mention of the throttle being on, is there?

You will have to have SOME throttle else the plane will go backwards with motion of the treadmill via drag.

[IndianStig]

not if the momentum, actuall your right, but if the plane is not moving from point a-b then all that trottle is useless, as there is no airflow that will get teh plane up, caus its standing still

[Ruiner]

not if the momentum, actuall your right, but if the plane is not moving from point a-b then all that trottle is useless, as there is no airflow that will get teh plane up, caus its standing still

Right, but, here is the catch: About the same amount of throttle to keep the plane stationary on the conveyor belt will be needed no matter if the conveyor belt is doing 50 or 1,000,000 miles per hour. Does this make sense to you?

[IndianStig]

yeah, if the friction on the wheels is constant

[Ruiner]

yeah, if the friction on the wheels is constant

Assuming that they don't break under the force (speed), then yes, the friction would be.

[SilverStoneZ]

there is no mention of the throttle being on, is there?

if its not on than the Plane speed = zero
and there would be no need for a question
because all = zero no throttle = no speed no speed = no movement from the conveyor

[Vteckidd]

it will not take off.

all things being constant. The planes wheels are not the driving force, they merely guide the plane, the engine is what propels it down the runway.

if the conveyor belt matches the speed at which the WHEELS of the plane are turning, in essense, there will not be forward motion. to create resistance or lift there must be air present, with a object essentially staying stationary, the plane cannot lift off.

but i failed math class and physics, so who know. Ruiner does make a compelling argument.

[Ruiner]

it will not take off.

all things being constant. The planes wheels are not the driving force, they merely guide the plane, the engine is what propels it down the runway.

if the conveyor belt matches the speed at which the WHEELS of the plane are turning, in essense, there will not be forward motion. to create resistance or lift there must be air present, with a object essentially staying stationary, the plane cannot lift off.

but i failed math class and physics, so who know. Ruiner does make a compelling argument.

Correct, the plane must move forward to make lift. You are correct in saying that the wheels are not the driving force. If they are not the driving force, then they should have no real bearing on the plane's motion, correct? Thus, if they do not affect the plane's motion, then it really won't matter how fast the conveyor belt is moving. If the plane gives SOME thrust, it will move forward.

However..........it is stated that the conveyor belt will match the plane's speed. The ONLY way for the plane to develop a "speed" is by moving forward. Thus, if the belt is doing 300mph, the plane is doing 300mph. That should be enough for the plane to develop lift (probably closer to 170-200knots, actually). If the plane is doing 500 knots, the conveyor belt would be doing 500 knots as well. However, the plane would be moving forward at that point.


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

[SilverStoneZ]

ok my last post as it looks like almost no one cares what i have to say is that the plane devlops its thurst from its force agenst the air not te run way thank you allwho actualy read my posts i am right i have checked it agenst a epartment of engineers working on the F22A rapter in marieta that all confirm all that i have said good night

[Vteckidd]

Correct, the plane must move forward to make lift. You are correct in saying that the wheels are not the driving force. If they are not the driving force, then they should have no real bearing on the plane's motion, correct? Thus, if they do not affect the plane's motion, then it really won't matter how fast the conveyor belt is moving. If the plane gives SOME thrust, it will move forward.

However..........it is stated that the conveyor belt will match the plane's speed. The ONLY way for the plane to develop a "speed" is by moving forward. Thus, if the belt is doing 300mph, the plane is doing 300mph. That should be enough for the plane to develop lift (probably closer to 170-200knots, actually). If the plane is doing 500 knots, the conveyor belt would be doing 500 knots as well. However, the plane would be moving forward at that point.
makes sense to me.

the only part i cant grasp is the "motion". if a plane is travelling at 400mph on this conveyor belt , then the plane has a speed correct? much like a car doing 140mph on my dyno, is really doing 140mph. but in a car the wheels ARE the driving force so i guess thats a bad example. i suppose if you put a jet engine on the back of a car on our dyno, it would create a "lift" because there will be some sort of thrust eventually, the car is at speen and in motion, and an object in motion stays in motion.

its kinda like, if your on top of a van. the van is moving 100mph, you jump str8 up, do you fall on the van or fall on the pavement, if there is no wind resistance.....

[Vteckidd]

Define Thrust please

[tony]

lol someone tried a video to explain

http://videos.streetfire.net/player.aspx?fileid=35E964D9-38DB-4EFD-BE8D-D6BA1A43A06B

[SilverStoneZ]

thurst is the forse created by the planes engins by creating resistance with the air behind it causeing the plane to move in a forward direction
the key to this whole question lies in the location of the moveing force and the wheels

[SilverStoneZ]

Bam exactly that video is all the proof anyone should need

[Vteckidd]

lol someone tried a video to explain

http://videos.streetfire.net/player.aspx?fileid=35E964D9-38DB-4EFD-BE8D-D6BA1A43A06B
that is all the proof i need

[Ruiner]

makes sense to me.

the only part i cant grasp is the "motion". if a plane is travelling at 400mph on this conveyor belt , then the plane has a speed correct? much like a car doing 140mph on my dyno, is really doing 140mph. but in a car the wheels ARE the driving force so i guess thats a bad example. i suppose if you put a jet engine on the back of a car on our dyno, it would create a "lift" because there will be some sort of thrust eventually, the car is at speen and in motion, and an object in motion stays in motion.

its kinda like, if your on top of a van. the van is moving 100mph, you jump str8 up, do you fall on the van or fall on the pavement, if there is no wind resistance.....

Yes, but speed on an airplane isn't measured through the wheels like it is on a car. :) THERE is your difference.

[Vteckidd]

Yes, but speed on an airplane isn't measured through the wheels like it is on a car. :) THERE is your difference.
AHA, now that i have a definition of thrust, then it makes snese

it WILL take off

[Ruiner]

AHA, now that i have a definition of thrust, then it makes snese

it WILL take off

Bingo. :)

Now, want me to really make people think?

What if there is a headwind that is increases/decreases speed to match the plane's speed? Will the plane take off? :)

[carrascopa]

sorry ruiner is right bout this one.. the treadmill scenario is perfect!!!!!

good job man...

[Vteckidd]

im gonna say yes cause there will still be thrust.

headwind is not the force BEHIND the planes engines. by his definition of thrust i beleive it will take off.


thurst is the forse created by the planes engins by creating resistance with the air behind it causeing the plane to move in a forward direction

[tony]

headwind will only enhance the planes ability to take off if I am not mistaken since headwind increases the planes airspeed moreso than its groundspeed.

[Ruiner]

headwind will only enhance the planes ability to take off if I am not mistaken since headwind increases the planes airspeed moreso than its groundspeed.

Yes, but will it move forward? :) Remember, the headwind is equal to the amount of thrust/forward motion. :)

[tony]

On one hand I want to say the headwind will actually push the 747 back keeping it on the conveyor BUT that same headwind could aid it in taking off.. even if the plane was not moving.

So I'll go with yes, it will still take off.

[Ruiner]

On one hand I want to say the headwind will actually push the 747 back keeping it on the conveyor BUT that same headwind could aid it in taking off.. even if the plane was not moving.

So I'll go with yes, it will still take off.

Actually, it will appear to "hover" in the air and not move forward or backwards if the wind is strong enough to keep it from going forward, but weak enough to not push it back. I know this because I have flown RC planes into strong headwinds and seen this effect with my own eyes.

[ISAtlanta300]

After some research on the original question, it will indeed take off. The wheels will just be moving at twice the speed of the conveyor......

[HEATON]

Jus go buy a toy model and try it with a tread mill..lol Be ur own dayum "MythBuster"

[Ruiner]

The wheels will just be moving at twice the speed of the conveyor......

No. The plane can still move forward and the wheels still spin backwards. :) Keep in mind that the wheels roll free. They really have no bearing on the plane's movement when all is said and done. The wheels can move backwards at 1000mph while the plane pushes forwards. The plane doesn't care. That is, of course, assuming that the wheel-brake isn't on. ;)

[Shawna]

ok my last post as it looks like almost no one cares what i have to say is that the plane devlops its thurst from its force agenst the air not te run way thank you allwho actualy read my posts i am right i have checked it agenst a epartment of engineers working on the F22A rapter in marieta that all confirm all that i have said good night


hahah I always knew you were smart...like father like son...i guess thats y he works where he has worked.

[MachNU]

Saw this on Supraforums and it was a pretty interesting read.

A plane (747 passenger jet) is sitting on a runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the planes speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).

The question is:

Will the plane (747 passenger jet) take off or not?

I would say that it wont take off. If this was in a closed room, where there was no opposite air flow moving under the wings then ti wont take off. Say even if you have a conveyor moving in the opposite direction of the plane, then the plane starts up thrust to move the plane forward to match the speed of the conveyor. But the way the question is worded, you said that the thurst and the conveyor would be moving at the same speed. Well for what you guys are saying that the wheels will beat the drag, then the thrust would have to have a constant gain of velocity, but the question is that they match the speed. So this question could almost be considered impossible becuase if you had a conveyor that could completely match the planes thrust, then you would have a machine that was 100% efficent. But in this situation if it could happen then they conveyor would match the speed of the belt for everybit of its gain on the belt the belt would jsut speed up.

I mean i could be wrong but from what i understand even if the wheels beat the drag, the belt would jsut speed up more, to coincide with the planes thrust. To me its the same way as saying if you had someone pushing an object with 50N of force to the north and then had someone pushing with 50N of force on the same object to the south, they woudl jsut cancel out!

[Ruiner]

I mean i could be wrong but from what i understand even if the wheels beat the drag, the belt would jsut speed up more, to coincide with the planes thrust. To me its the same way as saying if you had someone pushing an object with 50N of force to the north and then had someone pushing with 50N of force on the same object to the south, they woudl jsut cancel out!

You are wrong. Once the effects of the wheel drag are overcome, the plane will move forward. The "wheel drag" from free-rolling wheels is next to nothing as you and I both know. Remember the wheels are rolling free; not with brakes on. Mechanical wheel drag is relatively small. That "drag" is the ONLY thing working against the plane in reference to the conveyor belt.

[MachNU]

Yeah but to move the plane forward would require a huge conveyor area and then a huge tire area, then the wheels would have to have such grip that it pulls the conveyor nut the conveyor pulling it. Then if that had happened the plane could out trus the conveyor, but to me in a real life situation i dont think this would be possible. But still none the less fun to argue!

[chrisdavis]

You are wrong. Once the effects of the wheel drag are overcome, the plane will move forward. The "wheel drag" from free-rolling wheels is next to nothing as you and I both know. Remember the wheels are rolling free; not with brakes on. Mechanical wheel drag is relatively small. That "drag" is the ONLY thing working against the plane in reference to the conveyor belt.

Are you over coming wheel drag or the weight of the plane? I have been thinking about this. Once the engines over come the weight of the plane it will move forward regardless. The same way that a hovercraft only has to overcome the weight itself to move forward, the ground becomes a nonfactor once forward momentum is achieved so does the conveyor.

[Ruiner]

Yeah but to move the plane forward would require a huge conveyor area and then a huge tire area, then the wheels would have to have such grip that it pulls the conveyor nut the conveyor pulling it. Then if that had happened the plane could out trus the conveyor, but to me in a real life situation i dont think this would be possible. But still none the less fun to argue!

The wheels roll freely. There is no way for the simulation to take place as described under present-day physics.

[Ruiner]

Are you over coming wheel drag or the weight of the plane? I have been thinking about this. Once the engines over come the weight of the plane it will move forward regardless. The same way that a hovercraft only has to overcome the weight itself to move forward, the ground becomes a nonfactor once forward momentum is achieved so does the conveyor.

Overcoming the weight of the plane would require lift.

If you want a less "biased" test, think of it this way: Put your car in neutral with a jet engine on the back and let her rip...

No matter how fast the conveyor belt spins, the car's wheels will also spin at the same rate, backwards in line with the conveyor belt. HOWEVER, the thrust from the engine will push the car forward, even though the wheels are still spinning backwards... :)

[MachNU]

Overcoming the weight of the plane would require lift.

If you want a less "biased" test, think of it this way: Put your car in neutral with a jet engine on the back and let her rip...

No matter how fast the conveyor belt spins, the car's wheels will also spin at the same rate, backwards in line with the conveyor belt. HOWEVER, the thrust from the engine will push the car forward, even though the wheels are still spinning backwards... :)

Well from someone i talked to told me that there is no way for teh plane to move or lift off. Becuase if the belt matches the speed on the planes wheels then the plane will stay in the same spot becuase the thrusters are what moves the plane forward,so really the belt is matching hte speed of the thrust not the plane. So i still agree that the plane will just roll nad look likes it hovering in one spot.

[Ruiner]

Well from someone i talked to told me that there is no way for teh plane to move or lift off. Becuase if the belt matches the speed on the planes wheels then the plane will stay in the same spot becuase the thrusters are what moves the plane forward,so really the belt is matching hte speed of the thrust not the plane. So i still agree that the plane will just roll nad look likes it hovering in one spot.

No. You are missing what I am saying. If the plane has ENOUGH forward thrust to break the "drag" created by the wheels, it will move forward.

Now, understand this. The drag on the wheels will not really be any different if the belt is moving 200mph or 1,000mph. Let's say that that drag at 200mph on the wheels is 10lbs and the drag at 1,000mph is 10lbs. Does this make sense to you?

Thus, all it will take is 15lbs of thrust, no matter what the speed of the conveyor belt, to move forward as the drag of ~10lbs has been broken/overcome. Drag on the wheels will approach its limits. Drag will not increase (for the most part) past a certain mph on the conveyor belt.

Think of it this way: put a matchbox car on a treadmill. Put the treadmill on slow, medium, and fast speeds. Hold the car in one spot. Does it take MORE force to hold the car as the treadmill speeds increase? No. Why is that? The drag on the wheels reaches its theoretical limit at the lowest setting. Increasing the speed of hte treadmill does not increase the drag on the wheels as they are allowed to roll freely.

[B16a2 Civic]

no gas = no go.
my post is what matters, you guys are being way to technical

[MachNU]

Still the belt is moving at the same speed as the wheels, that means the thrust is what is moving the wheels, so if the thrust is moving the wheels then the belt is matching the speed of the thrust, and the plane can only produce so much thrust! Still if this was possible i would bet that the plane will stay in one spot no matter the amount of thrust.

[Ruiner]

Still the belt is moving at the same speed as the wheels, that means the thrust is what is moving the wheels, so if the thrust is moving the wheels then the belt is matching the speed of the thrust, and the plane can only produce so much thrust! Still if this was possible i would bet that the plane will stay in one spot no matter the amount of thrust.

No. The wheels roll freely. The thrust is not moving the wheels. The plane doesn't care about the wheels because they roll freely. The wheels don't really play a part EXCEPT for the small amount of drag that is produced as they spin. That's it. The drag is VERY small. Does that make sense?

Read what I said in my previous response to you...

[Speedm0(\)key]

:headslap: damn.. you guys are still going at it?

[Ruiner]

:headslap: damn.. you guys are still going at it?

Apparently this concept is difficult for people to grasp? I have explained it 10 times now.

Once they understand that the wheels roll freely and are basically independent of the plane's motion, it will all become very clear for them.

[Speedm0(\)key]

Apparently this concept is difficult for people to grasp? I have explained it 10 times now.

Once they understand that the wheels roll freely and are basically independent of the plane's motion, it will all become very clear for them.

i get you if it counts for anything, hey dont you know discount tire mike?

[Ruiner]

i get you if it counts for anything, hey dont you know discount tire mike?

But of course. He is the ONLY person that I allow to put tires on my Porsche. Putting 315/25/19" tires on a 19" HRE is not an easy thing to do. Mike has skills...

[MachNU]

Still that doesnt matter if the wheels roll freely they are still rolling on the ground with the weight of the plane on them, so that means if they dont roll the plane doesnt move. So really the speed on the wheels even rolling freely, are moving at the same velocity as the force the thrusters are producing. This means that the belt is moving at the same velocity as the thrust is pushing.

[Ruiner]

Still that doesnt matter if the wheels roll freely they are still rolling on the ground with the weight of the plane on them, so that means if they dont roll the plane doesnt move. So really the speed on the wheels even rolling freely, are moving at the same velocity as the force the thrusters are producing. This means that the belt is moving at the same velocity as the thrust is pushing.

No. Think about it this way: Could the wheels on the plane, while it is flying, be rotating backwards if something was causing them to spin? Would that effect the forward thrust of the plane? Not much.

[MachNU]

Okay use your proof of the tredmill. If you but a free folling wheel like the wheel of a plane on a tredmill and put it against the belt and started the tredmill holding it in one spot would be easy. All you would need to do is use work from your arm to hold it there, but to move it forward you would have to use force by your arm of pushing it forward. BUT the question states that the belt will match the speed on the wheel. So if you then pushed the wheel forward with your arm (thrust) the belt would speed up to compensate for the gain in velocity of the wheel, there for the wheel would never go anywhere. So like you said the wheel is free rolling but with no air under the wings the free rolling wheels is what is holding the plane to the ground.

[Ruiner]

Okay use your proof of the tredmill. If you but a free folling wheel like the wheel of a plane on a tredmill and put it against the belt and started the tredmill holding it in one spot would be easy. All you would need to do is use work from your arm to hold it there, but to move it forward you would have to use force by your arm of pushing it forward. BUT the question states that the belt will match the speed on the wheel. So if you then pushed the wheel forward with your arm (thrust) the belt would speed up to compensate for the gain in velocity of the wheel, there for the wheel would never go anywhere. So like you said the wheel is free rolling but with no air under the wings the free rolling wheels is what is holding the plane to the ground.

Yet again, no. You are missing it...

Imagine a swimming pool with conveyer belt bottom. If you're floating at one end and start swimming towards the other, it doesn't matter if the bottom of the pool starts to shoot away in the opposite direction. You will continue to swim/move relative to the water and reach the other end.

So getting back to the plane on the conveyer belt - the wheels on the landing gear are there to minimise friction with the ground. That's all they do. The plane's engines provide thrust relative to the air, not the ground.

The plane in air is like the swimmer in water. It doesn't matter whether the bottom of the pool or the conveyer belt is moving in the opposite direction to the swimmer or plane. The medium through which the plane flies or the swimmer swims is the key. http://forum.physorg.com/html/emoticons/cool.gif

Newtons Third law (for every action there is an equal and opposite action) is why you are thinking the plane won't move. But the acting force in the plane is the propellers and not the wheels.

Read this if you want a longer explanation:



Manfred's in the airplane. Old Hack (http://forum.physorg.com/index.php?showtopic=2417&st=420#) has the Army-surplus crane fired up and he's picking up the J-3 and Manfred and carrying them over to Runway 27, which has been transformed into a 3,000-foot conveyor belt. It is a calm day. The conveyor drive is programmed so that if Manfred can start to move in the J-3, if he can generate any airspeed or groundspeed, the conveyor will move toward the east (remember Manfred and the J-3 are facing west) at exactly the speed of the air/groundspeed. Because the wind is calm, if Manfred can generate any indicated airspeed, he will also be generating precisely the same groundspeed. Groundspeed, of course being relative to the ground of the airport surrounding the conveyor belt runway. So, the speed of the conveyor belt eastbound will be the same as Manfred's indicated airspeed, westbound.

Manfred does his prestart checklist, holds the heel brakes, hits the starter and the little Continental up front clatters to life. Oil pressure comes up and stabilizes and Manfred tries to look busy because the eyes of the world are upon him, but all he can do is make sure the fuel is on and the altimeter and trim are set, then do a quick runup to check the mags and the carb heat. He moves the controls through their full travel and glares at the ailerons, doing his best to look heroic, then holds the stick aft in the slipstream to pin the tail and lets go of the brakes.

Baron of the Belt

So far the J-3 has not moved, nor has the conveyor. At idle power, there's not enough thrust to move the J-3 forward on a level surface, so Manfred starts to bring up the power, intending to take off. The propeller rpm increases and the prop shoves air aft, as it does on every takeoff, causing the airplane to move forward through the air, and as a consequence, forward with regard to the ground. Simultaneously the conveyor creaks to life, moving east, under the tires of the J-3. As the J-3 thrusts its way through the air, driven by its propeller, the airspeed indicator comes off the peg at about 10 mph. At that moment the conveyor is moving at 10 mph to the east and the tires are whirling around at 20 mph because the prop has pulled it to an airspeed, and groundspeed, of 10 mph, westbound. The airplane is moving relative to the still air and the ground at 10 mph, but with regard to the conveyor, which is going the other way at 10 mph, the relative speed is 20 mph.

Manfred relaxes a bit because the conveyor cannot stop him from moving forward. There is nothing on the airplane that pushes against the ground or the conveyor in order for it to accelerate; as Karen -- one of our techies (http://forum.physorg.com/index.php?showtopic=2417&st=420#) here at the Lounge -- put it, the airplane freewheels. In technical terms, there is some bearing drag on the wheels, but it's under 40 pounds, and the engine has overcome that for years; plus the drag doesn't increase significantly as the wheel speed increases. Unless Manfred applies the brakes, the conveyor cannot affect the rate at which the airplane accelerates.

A few moments later, the roaring Continental, spinning that wooden Sensenich prop, has accelerated the J-3 and Manfred to 25 mph indicated airspeed. He and the airplane are cruising past the cheering spectators at 25 mph, while the conveyor has accelerated to 25 mph eastbound, yet it still has no way of stopping the airplane's movement through the air. The wheels are spinning at 50 mph, so the noise level is a little high, but otherwise, the J-3 is making a normal, calm-wind takeoff.

As the indicated airspeed passes 45 mph, groundspeed -- you know, relative to where all those spectators are standing beside the conveyor belt -- is also 45 mph. (At least that's what it says on Manfred's GPS (http://forum.physorg.com/index.php?showtopic=2417&st=420#). Being brought back to life seemed to create an insatiable desire for electronic stuff.) The conveyor is also at 45 mph, and the wheels are whizzing around at 90 -- the groundspeed plus the speed of the conveyor in the opposite direction.

Manfred breaks ground, climbs a few hundred feet, then makes a low pass to see if he can terrify the spectators because they are Americans, descendants of those who defeated his countrymen back in 1918.

It's All About Airspeed

While the speed of the conveyor belt in the opposite direction is superficially attractive in saying the airplane cannot accelerate, it truly is irrelevant to what is happening with the airplane, because the medium on which it is acting is the air. The only time it could be a problem is if the wheel speed got so high that the tires blew out.

I'm reminded of the New York Times editorial when Robert Goddard's rocket experiments were first being publicized. The author of the editorial said that rockets can't work in space because they have nothing to push against. It was laughably wrong, ignoring one of Sir Isaac's laws of physics that for every action there is an equal and opposite reaction. Here the propeller is pushing against the air, as it does every time an airplane takes off. How fast the airplane is moving over the surface on which its wheels rest is irrelevant; the medium is the magic. On a normal takeoff -- no conveyor involved -- if there is a 20 mph headwind, Manfred and the J-3 will lift off at 45 mph indicated airspeed; but relative to the ground, it is only 25 mph. Should the wind increase to 45 mph and if Manfred can get to the runway, he can take off without rolling an inch. His airspeed is 45 and groundspeed is zero. It is not necessary to have any groundspeed to fly, just airspeed. Conversely, if Manfred has a lot of runway and nothing to hit, and takes off downwind in a 25 mph tailwind, the propeller will have to accelerate the airplane to a zero airspeed, which will be a 25 mph groundspeed, and then on to a 45 mph airspeed, which will have him humming across the ground at 70 mph. The speed over the ground, or a conveyor belt, when an airplane takes off is irrelevant; all that matters is its speed through the air, and unless the pilot sets the brakes, a moving conveyor belt -- under the freely turning wheels -- cannot stop the process of acceleration.

Things eventually calmed down as the number of "it won't fly" folks dwindled as they began to understand that the airplane would take off. Old Hack looked at me and suggested we depart as the few holdouts showed no sign of changing their position. So, we headed out into the night to watch the guys take the conveyor out and reinstall the runway.

[MachNU]

Thats different though becuase that is a propeller plane. The propeller is used to pull air toward it. The question is what i am getting at. If you put a Boeing 747 in a closed huge facility with no wind, then placed it on a mile long belt then tried to get it to move it would stand still. The question states that if the belt could match the speed on the plane for every increase then the plane would sit in the same spot. EVEN though the thrust is pushing the air, there is no wind under the wings to pull the wheels off the ground, so there for the plane is being guided by its wheels. If the thrust pushes the plane forward on a runway then the plane would speed up to the point where there was enough lift under the wings to get it off the ground. But in this situation there is no lift under the wings so there for the wheels are holding the plane to the ground. So really the belt is moving at the same speed on the thrust which the wheels are holding that thrust to the ground so there for it wouldnt go anywhere.

But this situation is impossible becuase if this was possible the wheels would overheat and blow long before it could be tested.

[Ruiner]

Thats different though becuase that is a propeller plane. The propeller is used to pull air toward it. The question is what i am getting at. If you put a Boeing 747 in a closed huge facility with no wind, then placed it on a mile long belt then tried to get it to move it would stand still. The question states that if the belt could match the speed on the plane for every increase then the plane would sit in the same spot. EVEN though the thrust is pushing the air, there is no wind under the wings to pull the wheels off the ground, so there for the plane is being guided by its wheels. If the thrust pushes the plane forward on a runway then the plane would speed up to the point where there was enough lift under the wings to get it off the ground. But in this situation there is no lift under the wings so there for the wheels are holding the plane to the ground. So really the belt is moving at the same speed on the thrust which the wheels are holding that thrust to the ground so there for it wouldnt go anywhere.

But this situation is impossible becuase if this was possible the wheels would overheat and blow long before it could be tested.

Grrrrrrrrrrrrr. No. SAME principle. Prop, jet engine, they are BOTH THE SAME! You are not getting this, I can see. The belt moves at the same speed as the jet. A jet's speed is measured by the air flow, NOT by the wheel speed. Understand this? Do you expect to keep a plane on the ground, not developing lift, when it is moving at 400mph!?!? I don't care of the conveyor belt is moving at 400mph. The fact is that the conveyor belt is moving on the ground and has NO affect on the air; something that the jet engine relies 100% on to develop thrust.

The plane is going against the air while the conveyor belt is going against (what little bit) the wheels. Listen to me: THE WHEELS DO NOT DO ANYTHING BUT ALLOW FOR THE PLANE TO ROLL. That's it. The engine will provide thrust against the air. The conveyor belt has NOTHING to do with it (aside from drag on wheels that roll freely). The conveyor belt DOES NOT affect the air flow.

So getting back to the plane on the conveyer belt - the wheels on the landing gear are there to minimise friction with the ground. That's all they do. The plane's engines provide thrust relative to the air, not the ground.

The plane in air is like the swimmer in water. It doesn't matter whether the bottom of the pool or the conveyer belt is moving in the opposite direction to the swimmer or plane. The medium through which the plane flies or the swimmer swims is the key. http://forum.physorg.com/html/emoticons/cool.gif

Newtons Third law (for every action there is an equal and opposite action) is why you are thinking the plane won't move. But the acting force in the plane is the jet engine and not the wheels.

[/thread]

[Ruiner]

Read this again:


A few moments later, the roaring Continental, spinning that wooden Sensenich prop, has accelerated the J-3 and Manfred to 25 mph indicated airspeed. He and the airplane are cruising past the cheering spectators at 25 mph, while the conveyor has accelerated to 25 mph eastbound, yet it still has no way of stopping the airplane's movement through the air. The wheels are spinning at 50 mph, so the noise level is a little high, but otherwise, the J-3 is making a normal, calm-wind takeoff.

As the indicated airspeed passes 45 mph, groundspeed -- you know, relative to where all those spectators are standing beside the conveyor belt -- is also 45 mph. (At least that's what it says on Manfred's GPS. Being brought back to life seemed to create an insatiable desire for electronic stuff.) The conveyor is also at 45 mph, and the wheels are whizzing around at 90 -- the groundspeed plus the speed of the conveyor in the opposite direction.

IT IS ALL ABOUT AIRSPEED! No airspeed = no conveyor belt movement.

Speed for speed, remember? You cannot compare airspeed (plane) to groundspeed (conveyor belt) in this case. It is the fatal flaw of the original question.

[RandomGuy]

hrm... ruiner... why are we negating gravity?
Just wondering... say the Airplane was afloat and in zero gravity conditions then the wheels on the turner would have no effect right?

But there are 2 forces on the plane, the force of gravity down and the force of the thrust forward.... Right?

hrm i dont know my logic is likely wrong, but it seems like the plane would NOT lift off.

[SilverJester]

Ok I read the first 4 pages and got tired of reading. So here's the answer...
The plane is not going to take off. The plane needs air flowing under it's wings to take off. The only way to achieve that is by moving at a certain speed. The speed is not calculated like a car's speedo (that's pseduo speed)....speed is distance/time. The plane moves 1 foot, the conveyor belt has moved 1 foot in the opposite direction.....thus it distance is 0; 0 distance divided by however long it would have taken to move 1 foot = 0 speed. The matchbox car on the treadmill example doesn't work, speed is distance/time no matter what is propelling the plane, the wheels or the jet engine, it irrelevant because it's speed si going to be matched by the convyor belt.

[MachNU]

SilverJester adn RandomGyuy thank you thats what i was getting at. Three is no air flow under the wings so there is no lift, there-for gravity is holding the plane to the ground and the blet is matching the speed of the thrust. So in this question the wheels are the key factor, untill they are off the ground they are the things holding this plane to the ground. The thrust is jsut what is moving the plane but with theblet going in the opposite direction the plane is not going anywhere sothere for there is no air flow under the wings!

[Ruiner]

hrm... ruiner... why are we negating gravity?
Just wondering... say the Airplane was afloat and in zero gravity conditions then the wheels on the turner would have no effect right?

But there are 2 forces on the plane, the force of gravity down and the force of the thrust forward.... Right?

hrm i dont know my logic is likely wrong, but it seems like the plane would NOT lift off.

I did NOT negative gravity. That falls into the "drag" that I was talking about. It will "lift" when there is enough forward thrust. No matter have fast the conveyor belt is spinning backwards, once the plane gets enough forward thrust, it will take off. The conveyor belt would have no way to keep that down as it is only spinning the wheels while the thrust is working on the air.

[Ruiner]

SilverJester adn RandomGyuy thank you thats what i was getting at. Three is no air flow under the wings so there is no lift, there-for gravity is holding the plane to the ground and the blet is matching the speed of the thrust. So in this question the wheels are the key factor, untill they are off the ground they are the things holding this plane to the ground. The thrust is jsut what is moving the plane but with theblet going in the opposite direction the plane is not going anywhere sothere for there is no air flow under the wings!

NO! Why are you not listening to me? The belt ONLY affects the rate at which the wheels spin. If the plane is on a NORMAL runway that doesn't move, it will "ride" on the ground until it gets enough thrust (air over the wings) to generate lift. Now, if the runway is moving under it (conveyor belt), that DOES NOT matter.

It goes back to the swimmer in the swimming pool example. The belt DOES NOT affect the airflow. Can you understand this? The conveyor belt is not really able to affect the plane as the wheels roll freely.

Let me restate this:
- wheels roll freely
- wheels are the ONLY contact that the conveyor belt has with the plane
- gravity acts on the plane the same no matter if the runway is moving or not
- the conveyor belt DOES NOT affect the air
- thrust is acting against the air and the conveyor belt is acting against the wheels; which roll freely!
- once the engines get enough forward thrust, it WILL move forward.

Explain this to me:WHAT will keep the plane from moving forward?!?!? WHAT??? If the wheels are allowed to roll freely, WHAT will keep it from moving forward in terms of the conveyor belt?

[MachNU]

Dude there is no air flow nder the wings so there is no lift so there for the plane goes nowhere. If they start at the same speed and the plane thrust is started that is what pushed the plane forward, but at the same time the belt starts moving, there for the wheels are the only thing moving. The thrust is what accl. the plane, but if the wheels move at the same speed as the as the thrust can push it (this is on the ground the whole time) and there is no air flow under the wings (remember this is not outside where hte wind can pick up) then the plane will not lift or move forward!

[Ruiner]

Dude there is no air flow nder the wings so there is no lift so there for the plane goes nowhere. If they start at the same speed and the plane thrust is started that is what pushed the plane forward, but at the same time the belt starts moving, there for the wheels are the only thing moving. The thrust is what accl. the plane, but if the wheels move at the same speed as the as the thrust can push it (this is on the ground the whole time) and there is no air flow under the wings (remember this is not outside where hte wind can pick up) then the plane will not lift or move forward!


Explain this to me: WHAT will keep the plane from moving forward if there is forward thrust?!?!? WHAT??? Gravity? Yes, but that can be overcome as you and I both know. Drag on the wheels? It is very small, as they are free-rolling, but that is easily overcome. Weight of the plane? With enough forward thrust, that is negated as well, hence lift. If the wheels are allowed to roll freely, WHAT will keep it from moving forward in terms of the conveyor belt? How much force can the conveyor belt put on the plane? How much? If the plane has 300lbs of forward thrust, how much force can the conveyor belt, via the FREE ROLLING wheels, put on the plane?

Just answer me that. :)

[MachNU]

Explain this to me: WHAT will keep the plane from moving forward if there is forward thrust?!?!? WHAT??? Gravity? Yes, but that can be overcome as you and I both know. Drag on the wheels? It is very small, as they are free-rolling, but that is easily overcome. Weight of the plane? With enough forward thrust, that is negated as well, hence lift. If the wheels are allowed to roll freely, WHAT will keep it from moving forward in terms of the conveyor belt? How much force can the conveyor belt put on the plane? How much? If the plane has 300lbs of forward thrust, how much force can the conveyor belt, via the FREE ROLLING wheels, put on the plane?

Just answer me that. :)

Becuase the forward thrust is what gets the plane moving forwards. Now if the ground starts moving backwards then the plane is going to roll on the spot without moving forwards or backwards. The thrust is pretty much nothing more than accl. the thrust can push for all it was worth but with no air flow UNDEr the wings, the thrust pushes from behind the wings and back, so that stll produces no lift under the wings. There for the medium is the wheels. The example you used eariler about the two guys who tried the plane used is outside where there was still the slightest wing blowing and they used a propeller plane which wroduces a wind currect under the wings itself. A boeing does not it pushes itself forward, but if the ground under it goes nowhere then the plane goes nowhere.

[Vteckidd]

Im not gonna read this all, but Ruiner is right, given this scenario it WILL TAKE OFF.

My uncle flys for Delta, he said it will take off
My father is a Mathmatician (he got all the good genes) and said it will take off.

Interesting thing i was told , my uncle who flys for delta is a WWII historian as well, and he tld me something i thought was pretty cool. In WWII the old Biplanes, well, when they were on an aircraft carrier traveling at XXspeed. he said when the planes took off, they would actually almost immiedietly take flight due to the aircraft being in motion, and the wind coming across the Deck of the ship.

something to think about

[Ruiner]

Becuase the forward thrust is what gets the plane moving forwards. Now if the ground starts moving backwards then the plane is going to roll on the spot without moving forwards or backwards. The thrust is pretty much nothing more than accl. the thrust can push for all it was worth but with no air flow UNDEr the wings, the thrust pushes from behind the wings and back, so that stll produces no lift under the wings. There for the medium is the wheels. The example you used eariler about the two guys who tried the plane used is outside where there was still the slightest wing blowing and they used a propeller plane which wroduces a wind currect under the wings itself. A boeing does not it pushes itself forward, but if the ground under it goes nowhere then the plane goes nowhere.

Birthday:
July 21, 1987

You are talking to a college grad with many classes in physics and theory. Trust me on this, okay?

Do you know how jet engines work? A jet engine is like a prop, just with a TON of blades (I am simplifying this to an extent).

http://static.howstuffworks.com/gif/gas-turbine-turbofan2.gif


Here is your fallacy:


Becuase the forward thrust is what gets the plane moving forwards. Now if the ground starts moving backwards then the plane is going to roll on the spot without moving forwards or backwards.

The plane does not care about the ground. It only acts on the air. :) It DOES NOT care what the ground is doing IF it has free-rolling wheels. The AIR is what it cares about. If it can put force on the AIR, it will move forward. The wheels do not come into play as they are free-rolling! The conveyor belt can ONLY act on the wheels. However, I just told you that the plane does not care about the wheels. Thus, it does not care about the conveyor belt.

I asked you this earlier:

How much force can the conveyor belt put on the plane? How much? If the plane has 300lbs of forward thrust, how much force can the conveyor belt, via the FREE ROLLING wheels, put on the plane?

:)
:)
:)

[Vteckidd]

the answer is , the conveyor belt cant give any force against a free rolling wheels. that is the flaw in most peoples logic

[Ruiner]

the answer is , the conveyor belt cant give any force against a free rolling wheels. that is the flaw in most peoples logic

Exactly, sir. That is why I bolded that same question about "how much force can the conveyor belt put on the plane" in the question above your statement. He just doesn't get it.

[RandomGuy]

i c i knew i was wrong just wanted to know why... i c now, now if the plane were propelled by the wheels in relative to the ground, itd be a different story but thats not how it works... it makes sense... just a great scenario... surprised they never went over this scenario in physics

[Vteckidd]

maybe this will help:

I object only stays stationary when an EQUAL amount of force is applied in the opposite direction. Like a Dyno for instance, A car is moving 100mph, the car is being PULLED by ITS wheels. THe force is between the wheels and the Roller. A jet is not, a 747 is being PUSHED by its ENGINE. there is no force from the wheels of a jet.

Im also willing to bet if we didnt strap a car down on our dyno, if you did a pull it woul go forward, and jump off, the roller prob cant match the wheel speed fast enough, which is why cars are anchored down. to keep the forward motion from happening.

People cant get past the "well the plane is going one way, and the conveyor belt is going the other way, so its not moving therefor no wind happens." this is simply not true, the plane will move because NO MATTER HOW FAST THE CONVEYOR BELT TRAVELS, the force of the Plane being propelled by its engine will overcome the belts speed in relation to the planes wheels. then there will be forward motion, which will creat wind, which creates lift thrust etcetcetc.

/thread

[MachNU]

LOL i was just going by a Physics Professor answer to this. I just still believe that this question is impossible to prove. No matter what knowledge you may have i would still bet that if it was possible to prove this in a real live situation, i would still bet it doesnt take off. You can leave it at that, i may be wrong, but i am the type of person where you would haev to show me to prove me wrong.

[Vteckidd]

i understand where you are coming from, but the laws of physics prove its right that it will take off. its not rocket science, just a mind stumbler to most people.

Did Einstein have to PROVE his theory of relativity, or was his math enough to solidify his conclusions.

its all numbers man, and math DOESNT LIE

[MachNU]

True but math may not always be right, sometimes math may even over look the smallest thing that can make or break a theory. Odds are this will work but i would like to see it in action!