AiT.....trolly trolly trolly....Go back to the other sandbox and tell them you failed.

Well considering you can't create a conveyor belt that precisely follows the speed of the plane then we can't test exactly how it is worded. HOWEVER, since the conveyor doesn't matter at all...I am willing to bet you any amount up to $100,000,000 that the plane will take off

you down?

No way in hell it would take off. If man were meant to fly we'd be born with wings. Just a stupid idea all this flying nonsense.

<popcorn eating dude here>

Well, that's the point ******bag - it's a theoretical question.

Planes fly becasue of lift generated on the wings by airflow over them. On the conveyor belt, if the airplane is V=0 relative to everything other than the conveyor belt (the way the question was originally formulated), the only air movement there could be would be that small movement due to air friction with the belt, and that would be insufficient.

idiot....I wish i knew where you worked so I could send this to your boss so he could fire your ass for being a complete moron

Die thread Die

quote:

---

if the airplane is V=0 relative to everything other than the conveyor belt (the way the question was originally formulated)

---

The original question did not state this at all. Not even close.

The conveyor could be moving 100x faster than the plane and the plane would still take off.

If the plane can move ni a fashion such that it's motion relative to the air around it exceeds Vr, then it will fly.

The original qustion on this thread was not even a question - it was just an ill-formed statement that could be interpreted several ways.

The way I formulated the question is clear and concise - and one in which the airplane cannot fly.

Que TexasRebel
||
||
||
||
\ /
\/

[This message has been edited by TexasRebel (edited 12/14/2007 1:58p).]

oh yeah...me...

the plane either flies or does not fly depending on the assumption that you make...

assumption 1: The conveyor matches the wheel speed assumption...

This results in the plane not flying, and both the plane's gear and the conveyor being destroyed in a huge catastrophy. In this scenario, we will set the wheelspeed as the linear velocity that the wheels are turning x=2*radius(ft)*Pi*RPM/60 with the units [ft/s]
and y= the airspeed of the plane as measured by the instruments in the cockpit, and z= the linear speed the conveyor travels. Since the conveyor is matching the wheelspeed, we must find the speed that the wheels are turning. To keep it simple and still valid, we will simply say that the wheels are traveling at the airspeed of the plane + the speed of the conveyor (x = y + z). We also know that the speed of the conveyor is the same as the wheelspeed of the plane but in the opposite direction (z=x (because of the chosen coordinate system both can stay positive...if you work it out yourself be sure to pay atteniton to those negatives))...anyway, by substuting, you can now say that the wheels are traveling at the speed of the conveyor plus the speed of the wheels (x=y+x), and any 6th grader can tell you that as long as the speed of the conveyor is not 0 (y!=0) the equation is not true. Practically, this means that the conveyor is accelerating at an infinite rate...and in a perfectly balanced, flawless and competely efficent world the conveyor would eventually create enough friction in the landing gear of the plane and overcome the thrust of the engines (propellors or jets) and keep the plane stationary...

assumption 2: the conveyor matches the airspeed assumption...

in this scenario, the plane will fly...

we will define the airspeed of the plane as x, the speed of the conveyor as y, and the wheelspeed of the plane as z...

thrust will push the plane forward at the speed x. The conveyor will match that speed in the opposite direction (y=-x). Since the wheels are the contact medium between the two, the wheelspeed can be found with the equation z=x-y or z=x-(-x) or z=2x...which means the wheels are simply spinning twice as fast...the plane still moves forward because the thrust is an external force on the entire system. Unlike a car (which you are very obviuously basing your "testing" on) there is no mechanical link between an airplanes engines and the wheels that causes propulsion.

so, it depends on your assumption as to if the plane takes of, or causes catastropy...

[This message has been edited by TexasRebel (edited 12/14/2007 1:58p).]

quote:

---

idiot....I wish i knew where you worked

---

edit btb

[This message has been edited by CYFIN (edited 12/14/2007 2:03p).]

wow.

this thread is still moot.








and the plane still wont take off

You guys realize the engines aren't there to push wind over the wings right? They're there to provide enough force to propel the aircraft fast enough relative to the fluid that the plane is in (air) so that a lifting force can act on the wings.

If the plane does not have enough speed relative to the fluid that the aircraft is in there will not be a lifting force, so it goes nowhere.

I don't care if the plane is going 5000 mph but sitting still on a conveyor belt going -5000 mph because the air going over the wings is traveling at 0 mph.

The beautiful little plane is not going up.

[This message has been edited by McInnis 03 (edited 12/14/2007 2:11p).]

There's even a simpler way to convnice you morons.

The scenario I painted can be simulated by a glider on a conveyor belt. Tie a rope to the glider's nose and then tie it off to a tree.

Fire up the conveyor belt to whatever speed you like. The glider will, by definition, be traveling forward at exactly the same speed, except opposite direction, relative to the belt. it will never fly, unless the little bit of air being convected by the belt is sufficient for the glider to move up an inch or two - but it will promptly fall right back down once it hits air that is stationary relative to it.

quote:

---

The beautiful little plane is not going up.

---

thats what she said.

no **** it won't fly in that scenario...it isn't moving forward

I will concede that if the wheels fail and collapse due to the extreme stress place on them as their rotation approaches infinity before the plane takes off, then yes, the plane will crash. But assuming the wheels don't fail, then the plane takes off.

Or, maybe, doing this test will cause a rip in the universe's space/time fabric and we all die.

Oh, and yeah, if you tie the plane to a tree, then of course it won't take off. That was just a stupid example.


[This message has been edited by Mr. Cool Ice (edited 12/14/2007 2:11p).]

Is it then safe to assume that the thrust the engine produces would be tantamount to pulling on the string?

quote:

---

You guys realize the engines aren't there to push wind over the wings right? They're there to provide enough force to propel the aircraft fast enough relative to the fluid that the plane is in (air) so that a lifting force can act on the wings.

If the fluid that the aircraft is in does not generate enough speed so that the wings have a lifting force, it goes nowhere.

---

think for a second...

how does an airplane generate forward thrust?

doesn't it have something to do with that same fluid that the wings are going through? Yes

Does it have anything to do with those silly wheels that it sits on that can spin and spin all they want and create very little friction? No...

If the plane can push itself forward through the air, it can take off in the same air.

quote:

---

Is it then safe to assume that the thrust the engine produces would be tantamount to pulling on the string?

---

G or tampon?

[This message has been edited by NeuroticAg (edited 12/14/2007 2:11p).]

And that is exactly how I formulated the question. If the plane is moving forward relative to the air around it, it can fly. If it is not, it does not.

And here is the questions:

quote:

---

"A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?"

---

but you, like an idiot, are stating that the plane won't move forward (which is the actual question that it is asking)

AiT, in your scenario, what keeps the planes engines from creating forward thrust?

and don't say anything below the wings.

anything below the wings.

DIE DIE DIE DIE DIE DIE DIE DIE DIE

i don't think i have ever conversed with more idiotic people in my life...and I have spent quite a bit of time with mentally handicapped kids

quote:

---

All of the forward motion of the plane comes from the planes engines, which are in no way affected by the treadmill. The engines are grabbing air that is standing still in front of them, and pushing it away from the plane, the wheels are only along for the ride. Imagine if you had roller skates on your feet and were standing on a treadmill holding a stationary rope that outstretches in front of you. As the treadmill tries to push you backwards, your grasp on the rope keeps you stationary and your wheels spin. Now, someone begins to reel that rope in. The treadmill can try and compensate, but it only means your wheels spin faster, you will move forward in relative space. The same is true for the plane, only instead of grabbing a rope, the plane grabs the still air in front of it. If you were a passenger on such plane, you wouldn't even notice anything different was happening.

---

quote:

---

All of the forward motion of the plane comes from the planes engines, which are in no way affected by the treadmill. The engines are grabbing air that is standing still in front of them, and pushing it away from the plane, the wheels are only along for the ride. Imagine if you had roller skates on your feet and were standing on a treadmill holding a stationary rope that outstretches in front of you. As the treadmill tries to push you backwards, your grasp on the rope keeps you stationary and your wheels spin. Now, someone begins to reel that rope in. The treadmill can try and compensate, but it only means your wheels spin faster, you will move forward in relative space. The same is true for the plane, only instead of grabbing a rope, the plane grabs the still air in front of it. If you were a passenger on such plane, you wouldn't even notice anything different was happening.

---

Nothing - the impulse force from the engines keeps the plane moving forward relative to the conveyor belt. In my scenario, the engines only rev up to that thrust needed to overcome weight of the airplane * coefficient of friction.

In my glider example, the tension in the rope is equal to glider weight * coefficient of friction. It is analogous to thrust.

If the airplane has zero velocity relative to the air around it, the plane will not take off.

If the formulation of the problem is a word play where there are scenarios where the plane can move relative to the air, it can take off.

quote:

---

doesn't it have something to do with that same fluid that the wings are going through? Yes

Does it have anything to do with those silly wheels that it sits on that can spin and spin all they want and create very little friction? No...

If the plane can push itself forward through the air, it can take off in the same air.

---

If the plane is on a conveyor belt and has a forward speed of 200 mph and the belt has -200 mph speed you have zero velocity with respect to the air and to the ground.

This situation equals no lift.

Roller Girl >>>>>>>>>>>> Roller blades