quote Originally posted by Patrick: Saw this avatar in another forum: Is there no one who hasn't debated this topic?

Word has it that this question will be asked at the next Presidential Candidate Debate for both parties. The guy that answers correctly wins.

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Ron

It's the Soldier, not the reporter
Who has given us the freedom of the press.
It's the Soldier, not the poet,
Who has given us the freedom of speech.
It's the Soldier, not the politicians
That ensures our right to Life, Liberty and the Pursuit of Happiness.
It's the Soldier who salutes the flag,
Who serves beneath the flag,
And whose coffin is draped by the flag.

quote Originally posted by blackrams: Word has it that this question will be asked at the next Presidential Candidate Debate for both parties. The guy that answers correctly wins.

Hey, I know, I know, I know.

Gene For President

quote Originally posted by scrabblegod: Hey, I know, I know, I know. Gene For President

I might agree with you if "Gene" would ever answer his friggin phone.

------------------
Ron

It's the Soldier, not the reporter
Who has given us the freedom of the press.
It's the Soldier, not the poet,
Who has given us the freedom of speech.
It's the Soldier, not the politicians
That ensures our right to Life, Liberty and the Pursuit of Happiness.
It's the Soldier who salutes the flag,
Who serves beneath the flag,
And whose coffin is draped by the flag.

quote Originally posted by Patrick: Saw this avatar in another forum: Is there no one who hasn't debated this topic?

I saw it too. Notice the planes not moving?

quote Originally posted by Gokart Mozart: Notice the planes not moving?

Neither is the treadmill.

quote Originally posted by blackrams: I might agree with you if "Gene" would ever answer his friggin phone.

Check you r email or PMs

Ok let's try this. It says airplane. It doesn't say what kind. So let's use the aircraft Roger flew. An F-4 Phantom. Ok The Phantom had tons of power. Now Roger can comment on this more than I. BUT I am betting at full afterburner that plane would move even with full brakes on. So do you really bet that with brakes off that a it wouldn't move forward on a tread mill?

------------------
My sites
http://the-stickman.tripod.com

http://www.youtube.com/TheStickman

quote Originally posted by The_Stickman2: Ok let's try this. It says airplane. It doesn't say what kind. So let's use the aircraft Roger flew. An F-4 Phantom. Ok The Phantom had tons of power. Now Roger can comment on this more than I. BUT I am betting at full afterburner that plane would move even with full brakes on. So do you really bet that with brakes off that a it wouldn't move forward on a tread mill?

You're forgetting the people who think a conveyor belt with a magical control system can counteract several thousand pounds of thrust, and do so through freely rotating wheels.

If the conveyor moves opposite of the plane, how can the plane gain speed, move forward and gain lift under the wings?

Put the plane on full afterburners and release the brakes.
The plane starts to move forward.
The conveyor notices the speed of the plane and counteracts it.
After 1600 mph the conveyor is doing -1600.

Formula88, you're forgetting the plane has to go faster than the conveyor in order to gain lift.
It's not a static surface like a normal runway or a sheet of ice with a layer of oil on top.

The tires will burn up in any case and the plane can't move and won't fly.


The conveyor is indirectly opposing the force that is moving the plane forward, be it transmission, air thrust, jato engines, Atlas rocket or a push from someone.

[This message has been edited by Gokart Mozart (edited 12-30-2007).]

GoKart,

Lets just say that the plane is already traveling down a "fixed" runway at 150mph. Suddenly ahead of the plane the runway changes to a "conveyor belt" moving 150mph in the opposite direction.

What would happen to the plane?

There IS no super control system to instantly adjust the speed of the conveyor.
There IS no frictionless surface.
There IS a limit to how much a tire or bearings can take.
There is a limit to how fast a conveyor can move.
There is a limit on power output of a plane.
There is a limit on the rolling resistance of a plane.

This reminds me of the old question:
"Can God make a rock so big that he himself can't move it?" !!

To many unrealistic conditions.

A (flyable) plane always overcomes its rolling resistance and since that is the only force
the mystical conveyor has to counteract plane thrust, the plane will gain speed and fly.

quote Originally posted by TennT: A (flyable) plane always overcomes its rolling resistance and since that is the only force the mystical conveyor has to counteract plane thrust, the plane will gain speed and fly.

In other words, if a plane can move forward on a regular runway, why would a treadmill stop it? Or, if a regular runway doesn't stop the airplane from moving, why would a treadmill?

righto.
rollling resistance is all the conveyor has to push against to counter the
thrust of the plane's engine. Plane can already overcome its rolling resistance,
You have to have a balance of forces to stop the plane and rolling resistance
ain't enough.

quote Originally posted by Gokart Mozart: Formula88, you're forgetting the plane has to go faster than the conveyor in order to gain lift. It's not a static surface like a normal runway or a sheet of ice with a layer of oil on top. The conveyor is indirectly opposing the force that is moving the plane forward, be it transmission, air thrust, jato engines, Atlas rocket or a push from someone.

No, I'm not. I understand physics. The conveyor doesn't affect the speed of the plane. The plane moves forward and takes off normally. The conveyor could be going backwards FASTER than the plane, and the plane would still take off. We've already shown video proving that.

For the conveyor to oppose the force moving the plane, the conveyor has to be able to impart an equal and opposite force on the plane. If you stopped thinking about "speed" and started thinking about "forces" you might begin to understand.

Put on a pair of roller skates and stand on a treadmill. Hold yourself in place with one hand and turn the treadmill up to full speed with the other and answer for yourself how much "force" the treadmill is exerting on your arm. You only have to hold on hard enough to keep you from moving. The faster the treadmill goes, the force exerted on your arm doesn't noticeably increase. You can slowly pull yourself forward or or push yourself backward regardless of how fast the treadmill is going.

If your explanation was accurate, the treadmill would rip your arm off.

[This message has been edited by Formula88 (edited 12-30-2007).]

quote Originally posted by turbotoad: GoKart, Lets just say that the plane is already traveling down a "fixed" runway at 150mph. Suddenly ahead of the plane the runway changes to a "conveyor belt" moving 150mph in the opposite direction. What would happen to the plane?

The landing gear would break.
If we say the plane can withhold the stress, eventually the tires would be moving at 300 mph and the plane would sit still relative to the air.

If the plane is travelling 150 mph down a conveyor that's sitting still then the conveyor gets turned on 150 mph in the opposite direction, what woud happen?


TennT:
The premiss if the question is there is a super control system to instantly adjust the speed of the conveyor.

Formula88:
Let's think of it more of someone is holding your back. As you run, the treadmill keeps pace. When the hand pushes you, your speed increases and the treadmill speed increases.

quote Let's think of it more of someone is holding your back. As you run, the treadmill keeps pace. When the hand pushes you, your speed increases and the treadmill speed increases.

Oh, for 's sake.

Sorry, I just hate these hypothetical questions that don't consider all the
variables. It's fun sometimes to wonder what would happen IF, but all the
hard time I put in engineering making things that work in the real world
won't let me ignore all (or any of) the factors.
AND a "perfect" tracking system that runs a "perfect" conveyor on a plane with
"no" rolling resistance goes too much against my intuition.
All of this discussion does make you think though, doesn't it?

Lets say I’m on a treadmill that the belt can go 186.000 miles/second. I’m sitting in a wheelchair, with warp drive, and set the wheelchair to go warp 1, the speed of light, or 186,000 miles/second.

I have a flashlight in my lap, and point it forward. Will the light escape the flashlight, or will the photons stay on the bulb filament?

Also, will I appear frozen to an external observer not on the treadmill, and will I see them age and turn into skeletons and dust instantly?

Or will I engage in theoretical vs. practical physics arguments on the internet forever?

quote Originally posted by Gokart Mozart: The landing gear would break. If we say the plane can withhold the stress, eventually the tires would be moving at 300 mph and the plane would sit still relative to the air. If the plane is travelling 150 mph down a conveyor that's sitting still then the conveyor gets turned on 150 mph in the opposite direction, what woud happen? TennT: The premiss if the question is there is a super control system to instantly adjust the speed of the conveyor. Formula88: Let's think of it more of someone is holding your back. As you run, the treadmill keeps pace. When the hand pushes you, your speed increases and the treadmill speed increases.

Are you sure you don't do Physics Phone Support from India?

quote Originally posted by Raydar: Last January the New Orleans Times Picayune reported that a Cajun amateur archeologist having dug to a depth of 10 meters found traces of copper wire dating back 100 years.... and came to the conclusion that their ancestors already had a telephone network more than 100 years ago. Not to be outdone by the Cajuns, in the weeks that followed, Texas scientists dug to a depth of 20 meters. Shortly after, headlines in the Dallas Morning News read: ' Texas archaeologists have found traces of 200-year old copper wire, and have concluded that their ancestors already had an advanced high-tech communications network one hundred years earlier than the Cajuns.' One week later, The Atlanta Constitution reported the following: 'After digging as deep as 30 meters in fields near Donalsonville, GA. , Bubba Williams, a self-taught archeologist, reported that he found absolutely nothing. Bubba has therefore concluded that 300 years ago in Georgia they were already using wireless.'

You're not from Georgia are you?

[This message has been edited by Formula88 (edited 12-30-2007).]

quote Originally posted by Gokart Mozart: The landing gear would break. If we say the plane can withhold the stress, eventually the tires would be moving at 300 mph and the plane would sit still relative to the air.

Why would the landing gear break? You do realize that when a real/actual airplane lands at 150mph the wheels go from 0mph to 150mph INSTANTLY (or at least nearly instantly with a puff of smoke and some chirping) without the landing gear snapping. With a conveyor going 150mph in the opposite direction the wheels would go from 0mph to 300 mph instantly and the plane would still be traveling 150mph relative to the earth & air.

The original question does not say the conveyor "instanly" kick on at the opposite speed but that it instantly "matches" the speed of the plane. Therefore as the plane slowly increases speed so will the conveyor. So snapping landing gear is not even a factor.

quote If the plane is travelling 150 mph down a conveyor that's sitting still then the conveyor gets turned on 150 mph in the opposite direction, what woud happen?

As I said above, the wheels would instantly go from 150mph to 300mph. But the plane would still be traveling forward 150mph relative to the earth,wind and sky! The surface of the conveyor has no bearing on the forward mobility of the plane (unless the conveyor surface is thick mud).

quote TennT: The premiss if the question is there is a super control system to instantly adjust the speed of the conveyor.

But the whole conveyor and control system is a red herring! A misdirection! It has absolutely NO relationship to the froward momentum of the plane at all. THAT is the confusion. Mearly mentioning an opposite traveling conveyor somehow tricks the mind into thinking it must effect the plane somehow. It doesn't!

quote Formula88: Let's think of it more of someone is holding your back. As you run, the treadmill keeps pace. When the hand pushes you, your speed increases and the treadmill speed increases.

Aaaaarrrrggggg! Again, the conveyor/treadmill is a mis-direction. The plane is not connected in any way (other than it's wheels touching) to the conveyor. Your feet are the what propells your body. The wheels of the plane do not propell the plane body.

But as to the above;

"When the hand pushes you, your speed increases"............yes, so would the plane speed.

"and the treadmill speed increases".........yes, but the hand is an external sorce of forward force (same as the propellor thrust). It has no "solid connection" to the conveyor. You would have to move your feet faster (wheels turning) so you didn't fall over but you WOULD move forward in the direction of the push. I gaurantee the if you were running full speed on a tread mill and someone came up behind you and pushed as hard as they could, that you would fly forward and smash your face on the front bar!

Now if you had said that you simply began to RUN faster without the "external push", then yes, there would be no forward movement because the sorce of momentum (your feet) is directly related to the conveyor speed. But again, the planes forward propultion is not directly related to the speed of the conveyor. It is the external "hand" pushing the plane. So the conveyor plays absolutely no roll in the planes ability (or inability) to move forward and fly.

Phewwwww....I'm spent.

quote Originally posted by turbotoad: ...............Phewwwww....I'm spent.

Last time I said that, it was much more satisfying!!

You're in a small prop plane sitting on the conveyor. Your take off/max speed is 120 mph. The conveyor starts to move forward to 120 mph. How much power do you need to lift off?

None. You have the required speed to lift off. You need to turn the engine on or you'll become a glider.

----------------------------

You're in a small prop plane sitting on the conveyor pointing east. Your take off/max speed is 120 mph. It takes you 1 minute to reach that speed. The conveyor starts to move in reverse at 120 mph. What will happen?

A little over 2 miles west of where you started you'll be sitting still, running at full power. You can't take off because there's no lift.

---------------------------

The conveyor's power is electronically controlled by your throttle. You move your throttle forward 1/4, the conveyor rolls 1/4 in reverse. You give it full throttle, the conveyor moves max reverse. Can you fly?
No.

[This message has been edited by Gokart Mozart (edited 12-31-2007).]

Shouting and cussing doesn't help. You're still wrong.

wow.....

The cussing was a joke...

It still didn't change anything. I'm sorry you don't understand it. We've tried to explain it.

I made the same mistake when I first read the problem. I assumed the conveyor would counteract the plane's movement, so the plane wouldn't fly. Once I stopped and thought about it and how the plane pushes against the air rather than the runway to take off, I realized it would take off. The question is designed to lead you to the wrong conclusion. It never says the conveyor opposes or has any effect on the plane. You made that assumption, and that's where the error is.

The conveyor is keyed to the "plane's speed." Not the wheel speed, engine speed or engine thrust. If the plane moves forward, the conveyor moves backwards. If the plane was stationary, like you think it would be, the conveyor would stop because it's geared to the plane's speed. If the plane moves forward, it can take off. If the plane isn't moving forward, the conveyor isn't moving.

Your theory of the plane's engine running wide open with the plane stationary and the conveyor going backwards cannot happen because the plane's speed and the conveyor's speed wouldn't be the same.

[This message has been edited by Formula88 (edited 12-31-2007).]

I almost thought that too, several times.

I've tried to make it a point I'm not talking about wheel speed but I guess it needs to be addressed.
The plane pushes against the air, yes. I've said that several times.
The plane has to move down a runway to get to flight speed. That's why the runways are long. To gain speed (and to land but that's another story). As the plane gains speed, the air rushes around the wings, creating lift. We agree on this?


If the forward speed of the plane is countered by the reverse speed of the conveyor, how can air move around the wings?

quote Your theory of the plane's engine running wide open with the plane stationary and the conveyor going backwards cannot happen because the plane's speed and the conveyor's speed wouldn't be the same.

Which theory are you talking about? I want to be sure what you're rebutting.


air speed
0
plane speed
120
tire speed
240
conveyor speed
-120
ground speed
0

[This message has been edited by Gokart Mozart (edited 12-31-2007).]

Unlike a car, the wheels on the plane are "free-wheeling", and doesn't have any relation to the ground speed and the actual speed the plane is traveling.

If a treadmill is all it would take to stop a plane from taking off, then it can safely be assumed that the same treadmill could also assist the plane while taking off. Think about it. If all it took to stop a plane from taking off, is to stick it on a conveyor belt that was going the opposite direction; then you could spin the conveyor belt in the same direction, and drastically reduce the amount of distance it took for the plane to take off. Not to mention, when a plane was coming in for a landing; it could land on a conveyor belt that was spinning in the opposite direction, and the plane would instantly stop.

If that were actually the case, then I'm pretty sure that airports and aircraft carriers would both be using conveyor belts; instead of paying for all those long and expensive runways (airports), and catapult systems (aircraft carriers) and they'd build cheaper and smaller conveyor belts instead.

Point is, the conveyor belt has no bearing on the speed of the plane; as the wheels are "free-wheeling", and it's thrust, not torque that moves a plane. You could have a small prop plane sitting on a conveyor belt, and move that conveyor belt backwards at 1,000 MPH. The small prop plane will still power up, and move forward to it's max/takeoff speed of 120 MPH and fly. In the meantime, the wheels of the plane would be spinning at 1,120 MPH, but since they're "free-wheeling", it doesn't really matter. (Assuming that the wheel bearings can handle the stress).

quote Originally posted by Gokart Mozart: If the forward speed of the plane is countered by the reverse speed of the conveyor, how can air move around the wings? [

The conveyor simply cannot counter the motion of the plane, that is the problem with the theory.

quote Originally posted by Gokart Mozart: If the forward speed of the plane is countered by the reverse speed of the conveyor, how can air move around the wings?

Because the forward speed of the plane is NOT being countered. The force of the conveyor is being transferred to the wheels and spinning them, that is it. The only friction is between the tires and the conveyor, and that is not enough to hold back tens of thousands of pounds of jet thrust. Now, if the wheels did not spin, you would be right. But they do.

quote Originally posted by Gokart Mozart: If the forward speed of the plane is countered by the reverse speed of the conveyor, how can air move around the wings?

The forward speed of the plane is NOT countered. That's why air moves around the wings.

quote Originally posted by Gokart Mozart: Which theory are you talking about? I want to be sure what you're rebutting. air speed 0 plane speed 120 tire speed 240 conveyor speed -120 ground speed 0

Go back and read this over. You say the plane is going 120, the conveyor is going -120 and the wheels are going 240. Ok, I can agree with that. Your ground speed isn't 0, though. It's 120, and that's why the plane can take off. (relative to the conveyor, the ground speed is 240 - but relative to the earth, it's just 120. Airspeed is also 120, assuming 0 wind)

In order for the plane to be going 120 - the plane has to be moving.

When you say the plane is going 120, but the ground speed is 0, what are you saying the "plane speed" is?
What's going 120?

[This message has been edited by Formula88 (edited 12-31-2007).]

Here, I brought enough for everybody. (Except for Gokart, as he already has his hands full trying to figure out a way for that conveyor belt to stop the plane from flying).



Just kidding, Gokart, you can have some if you want.

quote Originally posted by Gokart Mozart: If the forward speed of the plane is countered by the reverse speed of the conveyor, how can air move around the wings?

The point you're missing is that the speed of one object cannot counter the speed of another. Speed is not the cause of movement. It's only a symptom. The cause (for the umpteenth time!) is FORCE.

Think of this: can a piece of paper moving at 10 MPH stop a bowling ball moving at 10 MPH? Using your (flawed) logic, the speed of the paper would counter the speed of the bowling ball. But that's not how it works. Because speed is not the deciding factor. The bowling ball has much more FORCE behind it than a piece of paper. So the bowling ball rolls through the paper like it's nothing.

Here's a more extreme example: you're on the International Space Station, and you launch a baseball at the Earth. You're positioned so that the Earth is moving towards you as it orbits the Sun. You launch the baseball towards the Earth at the same speed. Does the speed of the baseball counter the speed of the Earth? Does the Earth get stopped in its tracks by a baseball? OF COURSE NOT! FORCE is the deciding factor!

quote Originally posted by Blacktree:Here's a more extreme example: you're on the International Space Station, and you launch a baseball at the Earth. You're positioned so that the Earth is moving towards you as it orbits the Sun. You launch the baseball towards the Earth at the same speed. Does the speed of the baseball counter the speed of the Earth? Does the Earth get stopped in its tracks by a baseball? OF COURSE NOT! FORCE is the deciding factor!

This is a trick question. The ball would never hit the earth. It would either burn up in the atmosphere or start an orbit of it's own. Ok now back to the topic no one can agree on.

I cant believe this is still going on... is it going to keep going on until they do it on mythbusters? and then even after it? rofl this is so funny

[This message has been edited by AJ7 (edited 12-31-2007).]

quote Originally posted by The_Stickman2: This is a trick question. The ball would never hit the earth. It would either burn up in the atmosphere or start an orbit of it's own. Ok now back to the topic no one can agree on.

OK, substitute the Moon for Earth. The Moon has no atmosphere.

quote Originally posted by Deabionni: Unlike a car, the wheels on the plane are "free-wheeling", and doesn't have any relation to the ground speed and the actual speed the plane is traveling. If a treadmill is all it would take to stop a plane from taking off, then it can safely be assumed that the same treadmill could also assist the plane while taking off. Think about it. If all it took to stop a plane from taking off, is to stick it on a conveyor belt that was going the opposite direction; then you could spin the conveyor belt in the same direction, and drastically reduce the amount of distance it took for the plane to take off. Not to mention, when a plane was coming in for a landing; it could land on a conveyor belt that was spinning in the opposite direction, and the plane would instantly stop. If that were actually the case, then I'm pretty sure that airports and aircraft carriers would both be using conveyor belts; instead of paying for all those long and expensive runways (airports), and catapult systems (aircraft carriers) and they'd build cheaper and smaller conveyor belts instead. Point is, the conveyor belt has no bearing on the speed of the plane; as the wheels are "free-wheeling", and it's thrust, not torque that moves a plane. You could have a small prop plane sitting on a conveyor belt, and move that conveyor belt backwards at 1,000 MPH. The small prop plane will still power up, and move forward to it's max/takeoff speed of 120 MPH and fly. In the meantime, the wheels of the plane would be spinning at 1,120 MPH, but since they're "free-wheeling", it doesn't really matter. (Assuming that the wheel bearings can handle the stress).

Once again, I am not saying torque.

quote the wheels on the plane are "free-wheeling", and doesn't have any relation to the ground speed and the actual speed the plane is traveling

This sentence makes no sense.The wheels have no cause in the speed but they are drag. They usually are going the speed of the plane, which on the ground is ground speed.


How can a plane that has a max speed of 120 counter a 1000 reverse motion? It would be going 880 mph in reverse. It would need to move faster than the conveyor by 120 mph in order to lift off.


In real life the conveyor is impossible because it would have to withstand the force of a rolling (for example) 747-400ER takeoff weight of 910,000 lbs and the landing forces and still be flexible enough to rotate (not to mention climatic changes). Easier and cheaper to use a 12,000 foot runway.

Imagine the forces generated stopping a 747 traveling at 150 miles per hour, to a complete stop in about 320 feet and taking off in the same distance...

That same plane has 63,300 lbs thrust and a 180 mph take off speed.

How does the plane get up to 180? It rolls down a static runway, gaining speed against the ground, not the air. Once it reaches 180, lift is generated and flight is possible.

If the conveyor matches the speed of the plane, at 90 mph takeoff speed is generated. Do we agree on this?


If a plane is flying at 300 mph at max speed and encounters a headwind of 150 mph, how fast is the plane flying?


Ooh, ooh, ooh, I found something that helps my case.
http://www.sailingusa.info/...umber2a=0&number3a=0

[This message has been edited by Gokart Mozart (edited 12-31-2007).]

Answer my question. What's going 120 in your example?

Air speed = 0
Ground speed = 0
Plane speed = 120

quote Originally posted by Gokart Mozart: Which theory are you talking about? I want to be sure what you're rebutting. air speed 0 plane speed 120 tire speed 240 conveyor speed -120 ground speed 0

[This message has been edited by Formula88 (edited 12-31-2007).]

Wind is a totally different matter. Naturally opposing wind would stop an airplane's motion.