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

[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....D-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....D-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.