Can the airplane take off?

[smack Down]

Originally posted by: brikis98
ok, well, i tried. smack down, you're wrong again, but i'm not going to argue with you any more because either you are the most absurdly dense and ignorant person on earth or you are a troll and doing this to annoy us. if it's the former, i actually kind of pity you. if it's the latter, i hope you get banned because i am of the opinion that the higly technical forum is for serious discussions and not someone intentionally trying to irritate others. i'll be happy to continue this discussion with anyone else.

Not my fault you are wrong.

 

[vaca232]

Think of it like this. The plane is on the treadmill, the wheels are free moving. Tie a rope to the front of the plane and tie the other end to something NOT ON the treadmill in front of the plane. When the treadmill starts moving backwards, static friction causes the wheels to rotate. The only tension on the rope is the force equivalent to the friction between the freely moving wheels and the landing gear struts. That force is all the engines of the plane have to overcome to create positive acceleration. Say the rolling coefficient of friction for the aircraft is .015. Planes have a thrust to weight ratio much higher than that. There will be much more thrust pushing forwards, against the air not the treadmill, than friction pulling the plane backwards.

or, think of it like this.

You have a front wheel drive car with only its rear wheels on a treadmill. When you run the treadmill backwards the car will have a net force pushing it backwards. If you apply the brakes in the front wheels only, the friction of the brakes on the front wheels will equal the force pushing the car backwards. The force of the breaks is forward, to counteract the force backwards from the friction of the rear wheels. The force exerted on the car by the forward breaks will increase and remain equal and opposite to the force of friction on the rear wheels pushing the car backwards.

If you step on the gas just the right amount, the engine will drive the forward wheels with enough force to cancel out the friction pulling it back. If you step on the gas just a bit more the car will accelerate forward off of the treadmill.

The plane will take off because the engines thrust is independent from the treadmill-wheel system. As the plane accelerates down the treadmill, the treadmill accelerates in the opposite direction, increasing the force in the opposite direction the plane is moving, but that force will be much smaller than the forward force of the engines. The plane will always have a net force forward.

 

[smack Down]

Anyone that thinks ready the question such that the treadmill matches the speed of plane relitive to the treadmill surface is the wrong way to read the question please answer the following question.

If we replace the plane with a car will it move forward?

 

[Born2bwire]

Originally posted by: smack Down
Anyone that thinks ready the question such that the treadmill matches the speed of plane relitive to the treadmill surface is the wrong way to read the question please answer the following question.

If we replace the plane with a car will it move forward?

Now you're just being fvcking stupid.

 

[randay]

Originally posted by: smack Down
Anyone that thinks ready the question such that the treadmill matches the speed of plane relitive to the treadmill surface is the wrong way to read the question please answer the following question.

If we replace the plane with a car will it move forward?

Yes, the car will take off. you retard. now please answer the following question.

If we replace the car with your FACE, will you STFU?

 

[vaca232]

Originally posted by: smack Down
Anyone that thinks ready the question such that the treadmill matches the speed of plane relitive to the treadmill surface is the wrong way to read the question please answer the following question.

If we replace the plane with a car will it move forward?

The car would not move forward because the friction between the wheels and the surface (treadmill in this case) is what moves a car forward. The plane's engines have nothing to do with the treadmill at all. They push air, which is not affected by the treadmill

 

[smack Down]

Originally posted by: Born2bwire

Originally posted by: smack Down
Anyone that thinks ready the question such that the treadmill matches the speed of plane relitive to the treadmill surface is the wrong way to read the question please answer the following question.

If we replace the plane with a car will it move forward?

Now you're just being fvcking stupid.

So you don't know the answer and you are calling me stupid.

 

[sao123]

Originally posted by: smack Down
Anyone that thinks ready the question such that the treadmill matches the speed of plane relitive to the treadmill surface is the wrong way to read the question please answer the following question.

If we replace the plane with a car will it move forward?

cars are powered by wheels... the speed of the wheels determines how fast the car is going.

since when does the speed of the wheels determine how fast a plane goes?

thats right...they dont.

 

[smack Down]

Originally posted by: sao123

Originally posted by: smack Down
Anyone that thinks ready the question such that the treadmill matches the speed of plane relitive to the treadmill surface is the wrong way to read the question please answer the following question.

If we replace the plane with a car will it move forward?

cars are powered by wheels... the speed of the wheels determines how fast the car is going.

since when does the speed of the wheels determine how fast a plane goes?

thats right...they dont.

So your answer is ? yes or no?

 

[Smilin]

Originally posted by: Netopia
I only read the first page, but I'll try my hand at this. I seriously can't believe that ANYONE would think the plane would ever take off.

In the original question, the OP said that the treadmill would match the speed of the plane, only in reverse.

Let's assume that the plane needed 100MPH of air speed over the wings to get enough lift to become airborne.

Let's assume a 0 MPH relative wind speed.

If the plane generates enough thrust to move forward at 1 MPH, but the belt is going backward 1 MPH, the plane still has zero relative wind speed over the wings.

At enough thrust to move forward at 10 MPH, the belt is moving backward at 10 MPH and the plane still has a relative wind speed of ZERO over the wings.

At enough thrust to move forward at a MILLION miles per hour, the belt is moving backward at a million miles per hour and there is STILL no air flow over the wings to provide ANY lift!

Now, if a 100 MPH gust of head wind came out of nowhere, it's possible that the plane would INSTANTLY be airborne and be able to move forward because it already had enough thrust to keep it airborne ONCE ALOFT. But without air to create lift in the first place, it can never leave the conveyor belt.

If a boat was capable of going 10 MPH maximum and you headed it upstream in a river flowing at 10 MPH, do you think you'd move?

Maybe if we change venues it will be easier for some of you.... we have a runway on the Moon that is perfectly flat and goes all the way around the moon like a ring, there is no conveyor, and you have a normally shaped (but air tight) air liner, except that it has rocket engines that can fire for years on end. Will the plane ever get airborne? If you say "yes", you're an idiot. If you say no, you have your answer to why the one on earth wouldn't lift... YOU HAVE TO HAVE AIRSPEED FOR LIFT!

Joe

Netopia, you sir are WRONG.

I have highlighted three key points for you in your post above. The first boldface portion nearly earned you a flame. As for the second boldface portion:

You would only be correct sir if some dipsh1t forgot to release the parking brake on the plane!!!

Assuming there is no dipsh1t pilot like this the wheels will roll freely at 2mph (1mph for overall forward motion and airspeed of the plane + 1 mph for the backwards motion of the surface under the wheel).

for the third boldface portion: Your statement about the boat is perfectly correct...and also does not apply in the slightest to the airplane scenario. A boat propels itself by pushing against the water it sits in. A car with wheels propels itself by pushing against the ground (or treadmill it sits on). An Airplane does NOT propel itself by pushing against the ground (or treadmill) it sits on. It does so by pushing against the AIR it is sitting in....which in this case nobody has said is going backwards.

 

[Smilin]

Originally posted by: Smilin
Imagine a treadmill the length of an entire runway. Assume takeoff speed for the plane is 100knots.

Now assume we have three "speedometers".
1) The Pitot on the aircraft nose that measures airspeed.
2) A traditional speedometer, just like a car, that is connected to the aircraft wheel.
3) A traditional speedometer connected to one of the rollers on the treadmill.

Now imagine this:
Plane fires up the engines and applies thrust.
The plane accelerates to 100knots of airspeed per the Pitot (speedometer #1).
If it was a normal runway the speedometer #2 on the wheel would also show 100knots.

Now imagine the treadmill is moving backwards at the same speed that the plane is moving forward.
speedometer #1 (airspeed, pitot) shows +100knots.
speedometer #3 (on treadmill) shows -100knots (100 knots backwards).
speedometer #2 (plane wheels) shows +200knots (wheel moving forward through the air at 100, while rolling over surface goign backwards at 100 = spinning at 200.

PLANE WOULD TAKE OFF BECAUSE THE AIRSPEED IS 100 KNOTS.

Now if you spin the treadmill at 100knots backwards and LOCK THE BRAKES on the planes wheels you'll get this:
speedometer #1 (airspeed, pitot) shows -100knots (100 knots backwards).
speedometer #3 (treadmill) shows -100knots (100 backwards)
speedometer #2 (plane wheels) shows 0 knots...the wheels are locked so the plane goes at whatever speed the treadmill is going.

The plane would not take off because it's going 100knots backwards (it would likely flip all over the place and fall off the treadmill)

Now if you spin the treadmill FORWARD at 100 knots while the planes engines are driving it forward:
speedometer #1 (airspeed) = 100 knots.
speedometer #3 (treadmill) = 100 knots.
speedometer #2 (wheels) = 0 knots (the ground/treadmill is moving at same speed as plane's propeller is moving it forward).

Now if you spin the treadmill FORWARD at 100 knots and lock the brakes on the plane you'll get:
#1 (airspeed) = 100
#3 (treadmill) = 100
#2 (wheels) = 0 (same as before, but now you've allowed the airplane to take off without using it's own engine for propulsion...it will of course slow down and stop flying very shortly thereafter).

BEHOLD! THIS IS YOUR ANSWER. IT IS FINAL. SPEAK NO MORE OR BE DEEMED A FOOL!!!!!

 

[Gibsons]

Originally posted by: Smilin
BEHOLD! THIS IS YOUR ANSWER. IT IS FINAL. SPEAK NO MORE OR BE DEEMED A FOOL!!!!!

hmm

Two things are infinite: the universe and human stupidity; and I'm not sure about the universe.

-somebody smarter than me

 

[smack Down]

Originally posted by: Smilin

Originally posted by: Netopia
I only read the first page, but I'll try my hand at this. I seriously can't believe that ANYONE would think the plane would ever take off.

In the original question, the OP said that the treadmill would match the speed of the plane, only in reverse.

Let's assume that the plane needed 100MPH of air speed over the wings to get enough lift to become airborne.

Let's assume a 0 MPH relative wind speed.

If the plane generates enough thrust to move forward at 1 MPH, but the belt is going backward 1 MPH, the plane still has zero relative wind speed over the wings.

At enough thrust to move forward at 10 MPH, the belt is moving backward at 10 MPH and the plane still has a relative wind speed of ZERO over the wings.

At enough thrust to move forward at a MILLION miles per hour, the belt is moving backward at a million miles per hour and there is STILL no air flow over the wings to provide ANY lift!

Now, if a 100 MPH gust of head wind came out of nowhere, it's possible that the plane would INSTANTLY be airborne and be able to move forward because it already had enough thrust to keep it airborne ONCE ALOFT. But without air to create lift in the first place, it can never leave the conveyor belt.

If a boat was capable of going 10 MPH maximum and you headed it upstream in a river flowing at 10 MPH, do you think you'd move?

Maybe if we change venues it will be easier for some of you.... we have a runway on the Moon that is perfectly flat and goes all the way around the moon like a ring, there is no conveyor, and you have a normally shaped (but air tight) air liner, except that it has rocket engines that can fire for years on end. Will the plane ever get airborne? If you say "yes", you're an idiot. If you say no, you have your answer to why the one on earth wouldn't lift... YOU HAVE TO HAVE AIRSPEED FOR LIFT!

Joe

Netopia, you sir are WRONG.

I have highlighted three key points for you in your post above. The first boldface portion nearly earned you a flame. As for the second boldface portion:

You would only be correct sir if some dipsh1t forgot to release the parking brake on the plane!!!

Assuming there is no dipsh1t pilot like this the wheels will roll freely at 2mph (1mph for overall forward motion and airspeed of the plane + 1 mph for the backwards motion of the surface under the wheel).

for the third boldface portion: Your statement about the boat is perfectly correct...and also does not apply in the slightest to the airplane scenario. A boat propels itself by pushing against the water it sits in. A car with wheels propels itself by pushing against the ground (or treadmill it sits on). An Airplane does NOT propel itself by pushing against the ground (or treadmill) it sits on. It does so by pushing against the AIR it is sitting in....which in this case nobody has said is going backwards.

It doesn't matter that the plane pushes against the air. Using your definition of the control system a car would go forward just fine. The only difference would be the car would have to drive the wheel at 2 mph to get an overall forward speed of 1 mph. ! mph of wheel speed would go to over coming the backwards motion of the treadmill.

Ignoring friction both would require the exact same amount of energy. Assuming equal mass.

 

[wazzledoozle]

Originally posted by: kpb
That question doesn't make sense. A car which moves it's self foward using the wheels would be stationary relative to the ground if the conveyor was moving in the opposite direction at the same speed as the car is according to the speedometer. This is actually how they do a number of things on cars like testing horsepower and torque or how they figure out estimated mpg.

The problem with a plane is that the movement is generated by the jet engine or propeller and is not dependant on the wheels at all. They just support it and allow it to move foward until lift allows it to take off. So even if the conveyor belt was moving backwords the plane would still end up moving forwards and gaining speed. The wheels would just be turning twice as fast. The plane would either reach then end of the conveyor belt and crash or what ever or take off once it got enough speed. The conveyor belt wouldn't effect things at all really. The type of plane wouldn't change this at all because all planes must generate thier forward motion using an engine and not the wheels or they'd start loosing speed as soon as they took off =)

Yep.

 

[smack Down]

Originally posted by: wazzledoozle

Originally posted by: kpb
That question doesn't make sense. A car which moves it's self foward using the wheels would be stationary relative to the ground if the conveyor was moving in the opposite direction at the same speed as the car is according to the speedometer. This is actually how they do a number of things on cars like testing horsepower and torque or how they figure out estimated mpg.

The problem with a plane is that the movement is generated by the jet engine or propeller and is not dependant on the wheels at all. They just support it and allow it to move foward until lift allows it to take off. So even if the conveyor belt was moving backwords the plane would still end up moving forwards and gaining speed. The wheels would just be turning twice as fast. The plane would either reach then end of the conveyor belt and crash or what ever or take off once it got enough speed. The conveyor belt wouldn't effect things at all really. The type of plane wouldn't change this at all because all planes must generate thier forward motion using an engine and not the wheels or they'd start loosing speed as soon as they took off =)

Yep.

No. You just compared two different cases. In the first case talking about the car you are assuming the treadmill matchs the speed of the speedometer and when talking about the plane you assuming it matchs the ground speed. There is a world of difference between your to cases and can't be compared.

 

[Smilin]

Originally posted by: Gibsons

Originally posted by: Smilin
BEHOLD! THIS IS YOUR ANSWER. IT IS FINAL. SPEAK NO MORE OR BE DEEMED A FOOL!!!!!

hmm

Two things are infinite: the universe and human stupidity; and I'm not sure about the universe.

-somebody smarter than me

Einstein (and you misquoted). ;P

 

[Netopia]

Originally posted by: Smilin

Originally posted by: Netopia
I only read the first page, but I'll try my hand at this. I seriously can't believe that ANYONE would think the plane would ever take off.

In the original question, the OP said that the treadmill would match the speed of the plane, only in reverse.

Let's assume that the plane needed 100MPH of air speed over the wings to get enough lift to become airborne.

Let's assume a 0 MPH relative wind speed.

If the plane generates enough thrust to move forward at 1 MPH, but the belt is going backward 1 MPH, the plane still has zero relative wind speed over the wings.

At enough thrust to move forward at 10 MPH, the belt is moving backward at 10 MPH and the plane still has a relative wind speed of ZERO over the wings.

At enough thrust to move forward at a MILLION miles per hour, the belt is moving backward at a million miles per hour and there is STILL no air flow over the wings to provide ANY lift!

Now, if a 100 MPH gust of head wind came out of nowhere, it's possible that the plane would INSTANTLY be airborne and be able to move forward because it already had enough thrust to keep it airborne ONCE ALOFT. But without air to create lift in the first place, it can never leave the conveyor belt.

If a boat was capable of going 10 MPH maximum and you headed it upstream in a river flowing at 10 MPH, do you think you'd move?

Maybe if we change venues it will be easier for some of you.... we have a runway on the Moon that is perfectly flat and goes all the way around the moon like a ring, there is no conveyor, and you have a normally shaped (but air tight) air liner, except that it has rocket engines that can fire for years on end. Will the plane ever get airborne? If you say "yes", you're an idiot. If you say no, you have your answer to why the one on earth wouldn't lift... YOU HAVE TO HAVE AIRSPEED FOR LIFT!

Joe

Netopia, you sir are WRONG.

I have highlighted three key points for you in your post above. The first boldface portion nearly earned you a flame. As for the second boldface portion:

You would only be correct sir if some dipsh1t forgot to release the parking brake on the plane!!!

Assuming there is no dipsh1t pilot like this the wheels will roll freely at 2mph (1mph for overall forward motion and airspeed of the plane + 1 mph for the backwards motion of the surface under the wheel).

for the third boldface portion: Your statement about the boat is perfectly correct...and also does not apply in the slightest to the airplane scenario. A boat propels itself by pushing against the water it sits in. A car with wheels propels itself by pushing against the ground (or treadmill it sits on). An Airplane does NOT propel itself by pushing against the ground (or treadmill) it sits on. It does so by pushing against the AIR it is sitting in....which in this case nobody has said is going backwards.

You sir, committed the same sin I did by not reading the whole thread. Had you done that, you would have seen that I have already voluntarily eaten a well earned and healthy portion of humble pie, talkng with mouth full only enough to admit arrogance and incorrectness.

Joe

 

[sao123]

Originally posted by: smack Down

Originally posted by: wazzledoozle

Originally posted by: kpb
That question doesn't make sense. A car which moves it's self foward using the wheels would be stationary relative to the ground if the conveyor was moving in the opposite direction at the same speed as the car is according to the speedometer. This is actually how they do a number of things on cars like testing horsepower and torque or how they figure out estimated mpg.

The problem with a plane is that the movement is generated by the jet engine or propeller and is not dependant on the wheels at all. They just support it and allow it to move foward until lift allows it to take off. So even if the conveyor belt was moving backwords the plane would still end up moving forwards and gaining speed. The wheels would just be turning twice as fast. The plane would either reach then end of the conveyor belt and crash or what ever or take off once it got enough speed. The conveyor belt wouldn't effect things at all really. The type of plane wouldn't change this at all because all planes must generate thier forward motion using an engine and not the wheels or they'd start loosing speed as soon as they took off =)

Yep.

No. You just compared two different cases. In the first case talking about the car you are assuming the treadmill matchs the speed of the speedometer and when talking about the plane you assuming it matchs the ground speed. There is a world of difference between your to cases and can't be compared.

you're a moron.

 

[Smilin]

Originally posted by: smack Down
It doesn't matter that the plane pushes against the air. Using your definition of the control system a car would go forward just fine. The only difference would be the car would have to drive the wheel at 2 mph to get an overall forward speed of 1 mph. ! mph of wheel speed would go to over coming the backwards motion of the treadmill.

Ignoring friction both would require the exact same amount of energy. Assuming equal mass.

It certainly matters that the plane pushes against the air. Why does it matter?...because it makes anything happening under it on a free spinning wheel completely irrelevant.
You could put a stationary plane on a table cloth and yank it out. The plane would remain stationary while the planes wheels briefly spun. **Whatever is going on with the plane's wheels does not matter** They spin freely.

If the plane goes forward at 1mph, it goes forward at 1mph. If the wheels under it are on a treadmill going 50mph forward OR backwards it doesn't matter. That only determines how fast the wheels spin. The plane goes forward at 1mph.

If a car moves forward at 1mph on a treadmill going backwards at 1mph it's speedometer will register 2mph. The car is still moving forward at only 1mph. On the other hand if the car's speedometer says 1mph and it's sitting on a treadmill going backwards at 1mph then the car is stationary.

According to the question posed in this thread when the Airplane moves forward the treadmill moves backwards at the same speed.

"the airplane moves forward" = the airplane moves forward. Period.
"the treadmill moves backwards at the same speed" = the damn treadmill goes backwards at the same speed. Period.

The two are NOT mutually exclusive. You just have two objects going in opposite directions at the same speed. You therefore need some "grease" between them. This "grease" consists of a freely spinning landing gear wheel.

This wheel has a hub attached to one object and the outer circumference attached to another. It therefore spins at a rate which is the sum of the two.


I can't believe how dense everyone is on this thread. It's nuts. I've never seen the likes of it in the HT thread.


I think the big source of confusion here is this:
People are measuring the plane's speed by the rate at which it's wheel rotates rather than the speed at which the entire plane is moving.

If you say a plane is moving forward then the plane is moving forward. If the plane is sitting on a normal runway the airspeed and the wheel (ground) speed will be the same.

If the plane is sitting on a backwards moving treadmill but still going forward then the airspeed and the ground speed will not be the same. The groundspeed will be the airspeed + whatever rate the treadmill is rolling backwards at.


hell... it ain't gonna make the thread any longer we're already up to page 6. Lemme requote one more f'n time....

Originally posted by: Smilin

Originally posted by: Smilin
Imagine a treadmill the length of an entire runway. Assume takeoff speed for the plane is 100knots.

Now assume we have three "speedometers".
1) The Pitot on the aircraft nose that measures airspeed.
2) A traditional speedometer, just like a car, that is connected to the aircraft wheel.
3) A traditional speedometer connected to one of the rollers on the treadmill.

Now imagine this:
Plane fires up the engines and applies thrust.
The plane accelerates to 100knots of airspeed per the Pitot (speedometer #1).
If it was a normal runway the speedometer #2 on the wheel would also show 100knots.

Now imagine the treadmill is moving backwards at the same speed that the plane is moving forward.
speedometer #1 (airspeed, pitot) shows +100knots.
speedometer #3 (on treadmill) shows -100knots (100 knots backwards).
speedometer #2 (plane wheels) shows +200knots (wheel moving forward through the air at 100, while rolling over surface goign backwards at 100 = spinning at 200.

PLANE WOULD TAKE OFF BECAUSE THE AIRSPEED IS 100 KNOTS.

Now if you spin the treadmill at 100knots backwards and LOCK THE BRAKES on the planes wheels you'll get this:
speedometer #1 (airspeed, pitot) shows -100knots (100 knots backwards).
speedometer #3 (treadmill) shows -100knots (100 backwards)
speedometer #2 (plane wheels) shows 0 knots...the wheels are locked so the plane goes at whatever speed the treadmill is going.

The plane would not take off because it's going 100knots backwards (it would likely flip all over the place and fall off the treadmill)

Now if you spin the treadmill FORWARD at 100 knots while the planes engines are driving it forward:
speedometer #1 (airspeed) = 100 knots.
speedometer #3 (treadmill) = 100 knots.
speedometer #2 (wheels) = 0 knots (the ground/treadmill is moving at same speed as plane's propeller is moving it forward).

Now if you spin the treadmill FORWARD at 100 knots and lock the brakes on the plane you'll get:
#1 (airspeed) = 100
#3 (treadmill) = 100
#2 (wheels) = 0 (same as before, but now you've allowed the airplane to take off without using it's own engine for propulsion...it will of course slow down and stop flying very shortly thereafter).

Guys, my 55 year old mother gets this.

 

[Smilin]

Originally posted by: sao123

Originally posted by: smack Down
...something smackdown said...truncated here for brievity

you're a moron.

QFT.

 

[Smilin]

Originally posted by: Netopia
You sir, committed the same sin I did by not reading the whole thread. Had you done that, you would have seen that I have already voluntarily eaten a well earned and healthy portion of humble pie, talkng with mouth full only enough to admit arrogance and incorrectness.
Joe

You are quite correct. I have not read the entire thread. Pretty much just the first page then last few. If you have expressed the courage to admit a mistake of any magnitude I applaud you. It is not an easy thing to do.

Now, I will readily admit the sin of not reading the entire thread, but I am not yet ready to admit I am wrong about the original question.

The airplane WILL take off. See my thrice quoted explanation that involves the "three speedometers" for my view on the matter.

 

[Smilin]

Originally posted by: smack Down
Anyone that thinks ready the question such that the treadmill matches the speed of plane relitive to the treadmill surface is the wrong way to read the question please answer the following question.

This sentence makes no sense. I'll ignore it completely for now, please rephrase. I will go ahead and answer your question below but by doing so I am not saying I agree or disagree with your statement above. Again please clarify WTF you are talking about. "...that thinks ready the question..." Good lord man, ENGLISH!!!!

If we replace the plane with a car will it move forward?

Well. The original question said the airplane moves forward, so yes if you substitute a car it will move forward. The "airplane moving forward" part was one of the given conditions of the question.

If the treadmill is moving backwards at the same speed that the car is moving forward then the car's speedometer will register twice the car's actuall forward speed....with the GIVEN that the car is moving forward.

 

[smack Down]

"the airplane moves forward" = the airplane moves forward. Period.
"the treadmill moves backwards at the same speed" = the damn treadmill goes backwards at the same speed. Period.

Again moving forward can mean two things. It can move forward relitive to the treadmill surface yet stay put relitive to ground or it can move forward relitive to ground. Even if you assume relitive to ground if you take the limit of moving forward for adjusting the speed of the treadmill the airplane wouldn't move.

 

[TheVrolok]

"Highly technical"? No, it can't.

 

[bsobel]

Even if you assume relitive to ground if you take the limit of moving forward for adjusting the speed of the treadmill the airplane wouldn't move.

Sorry smilin, gotta try.

Ok, imagine that I am in a plane doing 200mph flying 5 feet over a treadmill running in the other direction at 200mph. I lower my landing gear. What occurs:

a) The wheels spin at 400mph (200mph forward plane motion + 200mph treadmill motion in the other direction)

b) The plane comes to an immediate halt killme as my body flies foward at 200mph (if so, please explain the physics involved)

c) Dogs and cats live together

Once you realize the answer is 'a' the problem is the same as originally stated.

Bill