Mythbusters to take on "the plane and the treadmill" conundrum?

[waggy]

Originally posted by: loic2003
dp

was not! you qouted yourself! i seen it!

 

[Tom]

Originally posted by: loic2003

Originally posted by: Tom

Originally posted by: waggy

Originally posted by: Citrix

Originally posted by: loic2003

Originally posted by: Phokus
can someone explain the conundrum plz?

You have a large treadmill/conveyor belt. It matches the speed of wheels, so if you put a car (or any vehicle that moves by physically turning it's wheels) and drove forward at 10mph, the mill would automatically move at 10mph in the opposite direction, so viewing the car from the side would show that the car doesn't actually move anywhere dispite it's wheels turning.

Then you take an airplane, and put that on the conveyor. Some idiots couldn't figure that planes use thrust to move, so wheel speed is irrelevant (think planes with skids for landing on snow or water). As the thrust of the plane moved it forward, the conveyor would try to keep up, but would always be slower than the aircraft's wheels since the plane is moving forward. Theoretically, the conveyor speed would increase (exponentially?) until the aircraft took off.

It really highlighted some serious idiots who thought planes had powered wheels or that the speed of the wheels made a difference to the thrust of the aircraft (bearing resistance has been ignored in this example).

you forget the thrust is to pull/push the A/C through space to create wind over the wings which will gives you lift. A plane on a treadmill going 100 miles an hour with the treadmill going 100 MPH against it would not create wind and would not create lift. the plane is staying in one spot and will not take off.

hmm the thing is that it really does not matter what the wheels or treadmill are doing.

the plane generates its foreword mementom from teh engines not the wheels. so no matter if the treadmill is going at any speed the thrust is going to move it.

what about my wheels chocks analogy ? Wheel chocks prevent the plane from moving, even though the thrust is not applied through the wheels.

Why is the force exerted by wheel chocks any different than the force exerted by an imaginary treadmill, that completely counteracts any forward motion of the wheels ?

Seems to me the only difference is in the case of wheel chocks, the wheels and chocks are stationary relative to each other, and in the treadmill case, the wheels and treadmills would be moving infinitely fast in opposite directions relative to each other.

The net effect in either case would be zero movement of the plane, relative to the air, wouldn't it ?

You're either flamebaiting or stupid.

EIf ti's the latter: think of a theoretical sailboat where the water offers no friction. the chocks represent the boats anchor.

Stick to the given problem. In your scenario though, which is completely different, if the water current was infinitely variable and matched the speed of the wind, the boat wouldn't move..

 

[waggy]

Originally posted by: Citrix

Originally posted by: Linflas

Originally posted by: Citrix

Originally posted by: freebee

Originally posted by: Citrix

Originally posted by: loic2003

Originally posted by: Phokus
can someone explain the conundrum plz?

You have a large treadmill/conveyor belt. It matches the speed of wheels, so if you put a car (or any vehicle that moves by physically turning it's wheels) and drove forward at 10mph, the mill would automatically move at 10mph in the opposite direction, so viewing the car from the side would show that the car doesn't actually move anywhere dispite it's wheels turning.

Then you take an airplane, and put that on the conveyor. Some idiots couldn't figure that planes use thrust to move, so wheel speed is irrelevant (think planes with skids for landing on snow or water). As the thrust of the plane moved it forward, the conveyor would try to keep up, but would always be slower than the aircraft's wheels since the plane is moving forward. Theoretically, the conveyor speed would increase (exponentially?) until the aircraft took off.

It really highlighted some serious idiots who thought planes had powered wheels or that the speed of the wheels made a difference to the thrust of the aircraft (bearing resistance has been ignored in this example).

you forget the thrust is to pull/push the A/C through space to create wind over the wings which will gives you lift. A plane on a treadmill going 100 miles an hour with the treadmill going 100 MPH against it would not create wind and would not create lift. the plane is staying in one spot and will not take off.

A plane going 100 mph (indicated) on a treadmill means the treadmill is going 100 mph. However, you've conveniently ignored the fact that the wheels are travelling in reverse at 200 mph, allowing the aircraft to take off.

Remember its true airspeed, not wheel speed like a car.

I didnt ignore anything. I know wheel speed has nothing to do with it. so tell me where the airspeed comes from? the plane is NOT MOVING. its the same as sitting at the hold line doing a full power check with the brakes on just before take off. the plane is not moving, there is no airspeed and there is no take off.

Yes i do fly small planes from time to time.

Then you should know that propellers are nothing more than rotating wings that are creating lift in the horizontal dimension pulling the plane forward. The wheels have zip to do with anything. In a perfectly frictionless environment you could run the treadmill at whatever speed you wanted and the plane would not move but the moment you pitch the prop to provide thrust the plane will pull itself forward.

wrong the props or a jet is not creating lift, its creating forward motion to create wind over the wings as the plane goes faster and faster down the runway and as the air pressure change reaches its magic formula you get lift.

a plane staying in one spot at full power is not moving there is no airpseed and will not take off period.

Exactly! the jet creates forward motion! no matter what the wheels are doing the plane creates forward motion!

at least you got part of it right. woot!

 

[OutHouse]

Originally posted by: Jeff7

Originally posted by: Linflas

Then you should know that propellers are nothing more than rotating wings that are creating lift in the horizontal dimension pulling the plane forward. The wheels have zip to do with anything. In a perfectly frictionless environment you could run the treadmill at whatever speed you wanted and the plane would not move but the moment you pitch the prop to provide thrust the plane will pull itself forward.

Yes, and for those who don't get how the plane could take off, keep this in mind: The speed of the plane is NOT dependent on the motion of the wheels. There are planes out there that don't have any wheels, planes which can take off from the water. So the conveyor belt could be moving at 2,000 miles per hour, but that doesn't matter. The wheels will just spin while the plane more or less sits there. Once it revs its engines, it will start to move forward. The wheels will say, "Holy hell this plane is going fast!" but the actual speed will be much lower. Then the plane takes off.

you forget the seaplane is moving forward across the water it is not staying in one spot.

 

[Zenmervolt]

Originally posted by: ultimatebob

Originally posted by: loic2003

Originally posted by: Phokus
can someone explain the conundrum plz?

You have a large treadmill/conveyor belt. It matches the speed of wheels, so if you put a car (or any vehicle that moves by physically turning it's wheels) and drove forward at 10mph, the mill would automatically move at 10mph in the opposite direction, so viewing the car from the side would show that the car doesn't actually move anywhere dispite it's wheels turning.

Then you take an airplane, and put that on the conveyor. Some idiots couldn't figure that planes use thrust to move, so wheel speed is irrelevant (think planes with skids for landing on snow or water). As the thrust of the plane moved it forward, the conveyor would try to keep up, but would always be slower than the aircraft's wheels since the plane is moving forward. Theoretically, the conveyor speed would increase (exponentially?) until the aircraft took off.

It really highlighted some serious idiots who thought planes had powered wheels or that the speed of the wheels made a difference to the thrust of the aircraft (bearing resistance has been ignored in this example).

Sounds good in theory, but I still doubt that they'll be able to get the plane to take off. The whole idea is just too impractical to work... If it did, airports would have short treadmill runways to save space.

I really don't know where to start.... There's just so much wrong with the reply...

OK, REGARDLESS of treadmill speed, the airplane moves forward. The thrust comes from Newton's 3rd law (every action has an equal and opposite reaction) and since the engines of the plane push the air backwards, the airplane is in turn thrust forwards. The entire treadmill part is a very cleaver red-herring that gives an excellent example of an area where traditional logic fails.

The first premise of the situation, that the treadmill always compensates for the plane's forward motion, is simply not possible. Ever. Given the manner in which a plane achieves forward motion it is not, and will never be, physically possible to have a treadmill that compensates for the plane's thrust. It violates the basic laws of physics.

The plane will take off. The plane will travel exactly as far down the treadmill as it would travel down a runway before taking off, and, functionally, it would feel no different at all from a normal takeoff using a runway. Anyone who thinks that the plane on the treadmill would remain stationary needs to go back to elementary school.

ZV

 

[Linflas]

Originally posted by: Citrix

Originally posted by: Linflas

Originally posted by: Citrix

Originally posted by: freebee

Originally posted by: Citrix

Originally posted by: loic2003

Originally posted by: Phokus
can someone explain the conundrum plz?

You have a large treadmill/conveyor belt. It matches the speed of wheels, so if you put a car (or any vehicle that moves by physically turning it's wheels) and drove forward at 10mph, the mill would automatically move at 10mph in the opposite direction, so viewing the car from the side would show that the car doesn't actually move anywhere dispite it's wheels turning.

Then you take an airplane, and put that on the conveyor. Some idiots couldn't figure that planes use thrust to move, so wheel speed is irrelevant (think planes with skids for landing on snow or water). As the thrust of the plane moved it forward, the conveyor would try to keep up, but would always be slower than the aircraft's wheels since the plane is moving forward. Theoretically, the conveyor speed would increase (exponentially?) until the aircraft took off.

It really highlighted some serious idiots who thought planes had powered wheels or that the speed of the wheels made a difference to the thrust of the aircraft (bearing resistance has been ignored in this example).

you forget the thrust is to pull/push the A/C through space to create wind over the wings which will gives you lift. A plane on a treadmill going 100 miles an hour with the treadmill going 100 MPH against it would not create wind and would not create lift. the plane is staying in one spot and will not take off.

A plane going 100 mph (indicated) on a treadmill means the treadmill is going 100 mph. However, you've conveniently ignored the fact that the wheels are travelling in reverse at 200 mph, allowing the aircraft to take off.

Remember its true airspeed, not wheel speed like a car.

I didnt ignore anything. I know wheel speed has nothing to do with it. so tell me where the airspeed comes from? the plane is NOT MOVING. its the same as sitting at the hold line doing a full power check with the brakes on just before take off. the plane is not moving, there is no airspeed and there is no take off.

Yes i do fly small planes from time to time.

Then you should know that propellers are nothing more than rotating wings that are creating lift in the horizontal dimension pulling the plane forward. The wheels have zip to do with anything. In a perfectly frictionless environment you could run the treadmill at whatever speed you wanted and the plane would not move but the moment you pitch the prop to provide thrust the plane will pull itself forward.

wrong the props or a jet is not creating lift, its creating forward motion to create wind over the wings as the plane goes faster and faster down the runway and as the air pressure change reaches its magic formula you get lift.

a plane staying in one spot at full power is not moving there is no airpseed and will not take off period.

Sorry but my original statement is correct.

Propellers
Airplane propellers act like small rotating wings, whose "lift" pulls the airplane forward (the pulling force is known as thrust). Possibly the greatest benefit derived by the Wright brothers from their wind tunnel was the help they got, not in planning their wings (a crude design, limited by available technology) but in the design of their propellers, which were twice as efficient as any others of their time.

(22c) Airplane Flight

 

[Tom]

Originally posted by: Linflas

Originally posted by: Tom

Originally posted by: waggy

Originally posted by: Citrix

Originally posted by: loic2003

Originally posted by: Phokus
can someone explain the conundrum plz?

You have a large treadmill/conveyor belt. It matches the speed of wheels, so if you put a car (or any vehicle that moves by physically turning it's wheels) and drove forward at 10mph, the mill would automatically move at 10mph in the opposite direction, so viewing the car from the side would show that the car doesn't actually move anywhere dispite it's wheels turning.

Then you take an airplane, and put that on the conveyor. Some idiots couldn't figure that planes use thrust to move, so wheel speed is irrelevant (think planes with skids for landing on snow or water). As the thrust of the plane moved it forward, the conveyor would try to keep up, but would always be slower than the aircraft's wheels since the plane is moving forward. Theoretically, the conveyor speed would increase (exponentially?) until the aircraft took off.

It really highlighted some serious idiots who thought planes had powered wheels or that the speed of the wheels made a difference to the thrust of the aircraft (bearing resistance has been ignored in this example).

you forget the thrust is to pull/push the A/C through space to create wind over the wings which will gives you lift. A plane on a treadmill going 100 miles an hour with the treadmill going 100 MPH against it would not create wind and would not create lift. the plane is staying in one spot and will not take off.

hmm the thing is that it really does not matter what the wheels or treadmill are doing.

the plane generates its foreword mementom from teh engines not the wheels. so no matter if the treadmill is going at any speed the thrust is going to move it.

what about my wheels chocks analogy ? Wheel chocks prevent the plane from moving, even though the thrust is not applied through the wheels.

Why is the force exerted by wheel chocks any different than the force exerted by an imaginary treadmill, that completely counteracts any forward motion of the wheels ?

Seems to me the only difference is in the case of wheel chocks, the wheels and chocks are stationary relative to each other, and in the treadmill case, the wheels and treadmills would be moving infinitely fast in opposite directions relative to each other.

The net effect in either case would be zero movement of the plane, relative to the air, wouldn't it ?

Apply enough thrust and the plane will go right over the chocks. When they do high power engine tests on aircraft they tie the aircraft down with tiedown chains into padeyes on the tarmac.

This is a theoretical problem, not based on reality. Your point has no bearing on a theoretical situation.

In real life, there's no such thing as an infinitely fast treadmill, so obviously in real life the plane would take off.

 

[OutHouse]

Originally posted by: waggy

Originally posted by: Citrix

Originally posted by: Linflas

Originally posted by: Citrix

Originally posted by: freebee

Originally posted by: Citrix

Originally posted by: loic2003

Originally posted by: Phokus
can someone explain the conundrum plz?

You have a large treadmill/conveyor belt. It matches the speed of wheels, so if you put a car (or any vehicle that moves by physically turning it's wheels) and drove forward at 10mph, the mill would automatically move at 10mph in the opposite direction, so viewing the car from the side would show that the car doesn't actually move anywhere dispite it's wheels turning.

Then you take an airplane, and put that on the conveyor. Some idiots couldn't figure that planes use thrust to move, so wheel speed is irrelevant (think planes with skids for landing on snow or water). As the thrust of the plane moved it forward, the conveyor would try to keep up, but would always be slower than the aircraft's wheels since the plane is moving forward. Theoretically, the conveyor speed would increase (exponentially?) until the aircraft took off.

It really highlighted some serious idiots who thought planes had powered wheels or that the speed of the wheels made a difference to the thrust of the aircraft (bearing resistance has been ignored in this example).

you forget the thrust is to pull/push the A/C through space to create wind over the wings which will gives you lift. A plane on a treadmill going 100 miles an hour with the treadmill going 100 MPH against it would not create wind and would not create lift. the plane is staying in one spot and will not take off.

A plane going 100 mph (indicated) on a treadmill means the treadmill is going 100 mph. However, you've conveniently ignored the fact that the wheels are travelling in reverse at 200 mph, allowing the aircraft to take off.

Remember its true airspeed, not wheel speed like a car.

I didnt ignore anything. I know wheel speed has nothing to do with it. so tell me where the airspeed comes from? the plane is NOT MOVING. its the same as sitting at the hold line doing a full power check with the brakes on just before take off. the plane is not moving, there is no airspeed and there is no take off.

Yes i do fly small planes from time to time.

Then you should know that propellers are nothing more than rotating wings that are creating lift in the horizontal dimension pulling the plane forward. The wheels have zip to do with anything. In a perfectly frictionless environment you could run the treadmill at whatever speed you wanted and the plane would not move but the moment you pitch the prop to provide thrust the plane will pull itself forward.

wrong the props or a jet is not creating lift, its creating forward motion to create wind over the wings as the plane goes faster and faster down the runway and as the air pressure change reaches its magic formula you get lift.

a plane staying in one spot at full power is not moving there is no airpseed and will not take off period.

Exactly! the jet creates forward motion! no matter what the wheels are doing the plane creates forward motion!

at least you got part of it right. woot!

and on a treadmill matching that forward motion exactly in the oposite direction totally negates the forward motion so the plane is not moving to create that lift.

 

[spidey07]

As stated in the original description it is impossible for the plane to move forward.

No lift = no takeoff.

 

[Zenmervolt]

Originally posted by: Citrix
wrong the props or a jet is not creating lift, its creating forward motion to create wind over the wings as the plane goes faster and faster down the runway and as the air pressure change reaches its magic formula you get lift.

a plane staying in one spot at full power is not moving there is no airpseed and will not take off period.

Firstly, a propellor is a rotating wing. It will pull the airplane forward unless something is anchoring the airplane or physically preventing the airplane's moving forward. A propellor, oriented horizontally, would generate lift. As normall oriented, it provides thrust. However, "lift" and "thrust" are simply directional qualifiers given to the same force. The same principle that causes a wing to generate lift causes a propellor to generate thrust.

Second, unless the axels have absurdly high friction, there is no way that the treadmill could ever generate sufficient friction to counteract the propellor's or jet's thrust.

The plane absolutely will not stay in one spot. It will move forward regardless of treadmill speed.

ZV

 

[Rob9874]

I had started to post my reasons for thinking the plane will not take off, however, once I started typing, I convinced myself that it would. Here's why. The "won't take off" people are thinking of the wheels as a car's. The car relies on the wheels to move it forward. On an airplane, the wheels are loose, and just there so the belly of the plane doesn't scrape along the runway.

Picture this scenario. Let's say you put your R/C plane on a treadmill, but you are beside the treadmill, with your hand on the plane. If you held the plane steady, the treadmill would be moving and the wheels of the plane would be spinning. But what would happen if you pushed the plane up the treadmill? Do you think that as long as the treadmill kept up with the speed of the wheels, you would not be able to push the plane from the back of the treadmill belt to the front? The wheels would just skid forward on the treadmill belt. That works, because the force pushing it forward (your hand), is not affected by the treadmill moving backwards. That is the same concept of engine thrust. It's an "invisible hand" pushing the airplane forward, independent of the treadmill.

 

[OutHouse]

Originally posted by: Rob9874
I had started to post my reasons for thinking the plane will not take off, however, once I started typing, I convinced myself that it would. Here's why. The "will take off" people are thinking of the wheels as a car's. The car relies on the wheels to move it forward. On an airplane, the wheels are loose, and just there so the belly of the plane doesn't scrape along the runway.

Picture this scenario. Let's say you put your R/C plane on a treadmill, but you are beside the treadmill, with your hand on the plane. If you held the plane steady, the treadmill would be moving and the wheels of the plane would be spinning. But what would happen if you pushed the plane up the treadmill? Do you think that as long as the treadmill kept up with the speed of the wheels, you would not be able to push the plane from the back of the treadmill belt to the front? The wheels would just skid forward on the treadmill belt. That works, because the force pushing it forward (your hand), is not affected by the treadmill moving backwards. That is the same concept of engine thrust. It's an "invisible hand" pushing the airplane forward, independent of the treadmill.

plane is still stationary, no wind no lift.

 

[Zenmervolt]

Originally posted by: spidey07
As stated in the original description it is impossible for the plane to move forward.

No lift = no takeoff.

THe original description defies the laws of physics. You may as well say, "if bernouli's principle were reversed, would an airplane fly".

There is not, and will never be, a treadmill that can compensate for an airplane's thrust.

ZV

 

[spidey07]

Originally posted by: Rob9874
I had started to post my reasons for thinking the plane will not take off, however, once I started typing, I convinced myself that it would. Here's why. The "won't take off" people are thinking of the wheels as a car's. The car relies on the wheels to move it forward. On an airplane, the wheels are loose, and just there so the belly of the plane doesn't scrape along the runway.

Picture this scenario. Let's say you put your R/C plane on a treadmill, but you are beside the treadmill, with your hand on the plane. If you held the plane steady, the treadmill would be moving and the wheels of the plane would be spinning. But what would happen if you pushed the plane up the treadmill? Do you think that as long as the treadmill kept up with the speed of the wheels, you would not be able to push the plane from the back of the treadmill belt to the front? The wheels would just skid forward on the treadmill belt. That works, because the force pushing it forward (your hand), is not affected by the treadmill moving backwards. That is the same concept of engine thrust. It's an "invisible hand" pushing the airplane forward, independent of the treadmill.

That's the correct thinking.

However it is impossible for the plane to advance given the wording of the scenario. It's a paradox. If the plane advances then it breaks the bounds of the problem.

 

[Zenmervolt]

Originally posted by: Citrix

Originally posted by: Rob9874
I had started to post my reasons for thinking the plane will not take off, however, once I started typing, I convinced myself that it would. Here's why. The "will take off" people are thinking of the wheels as a car's. The car relies on the wheels to move it forward. On an airplane, the wheels are loose, and just there so the belly of the plane doesn't scrape along the runway.

Picture this scenario. Let's say you put your R/C plane on a treadmill, but you are beside the treadmill, with your hand on the plane. If you held the plane steady, the treadmill would be moving and the wheels of the plane would be spinning. But what would happen if you pushed the plane up the treadmill? Do you think that as long as the treadmill kept up with the speed of the wheels, you would not be able to push the plane from the back of the treadmill belt to the front? The wheels would just skid forward on the treadmill belt. That works, because the force pushing it forward (your hand), is not affected by the treadmill moving backwards. That is the same concept of engine thrust. It's an "invisible hand" pushing the airplane forward, independent of the treadmill.

plane is still stationary, no wind no lift.

As explained a half-dozen times already, the plane does not remain stationary.

ZV

 

[spidey07]

Originally posted by: Zenmervolt
THe original description defies the laws of physics. You may as well say, "if bernouli's principle were reversed, would an airplane fly".

There is not, and will never be, a treadmill that can compensate for an airplane's thrust.

ZV

Of couse there isn't. But according to the definitions, plane can't move forward. If it does then we are no longer talking about the same scenario.

 

[sao123]

Originally posted by: Tom

Originally posted by: freebee

Originally posted by: Citrix

Originally posted by: loic2003

Originally posted by: Phokus
can someone explain the conundrum plz?

You have a large treadmill/conveyor belt. It matches the speed of wheels, so if you put a car (or any vehicle that moves by physically turning it's wheels) and drove forward at 10mph, the mill would automatically move at 10mph in the opposite direction, so viewing the car from the side would show that the car doesn't actually move anywhere dispite it's wheels turning.

Then you take an airplane, and put that on the conveyor. Some idiots couldn't figure that planes use thrust to move, so wheel speed is irrelevant (think planes with skids for landing on snow or water). As the thrust of the plane moved it forward, the conveyor would try to keep up, but would always be slower than the aircraft's wheels since the plane is moving forward. Theoretically, the conveyor speed would increase (exponentially?) until the aircraft took off.

It really highlighted some serious idiots who thought planes had powered wheels or that the speed of the wheels made a difference to the thrust of the aircraft (bearing resistance has been ignored in this example).

you forget the thrust is to pull/push the A/C through space to create wind over the wings which will gives you lift. A plane on a treadmill going 100 miles an hour with the treadmill going 100 MPH against it would not create wind and would not create lift. the plane is staying in one spot and will not take off.

A plane going 100 mph (indicated) on a treadmill means the treadmill is going 100 mph. However, you've conveniently ignored the fact that the wheels are travelling in reverse at 200 mph, allowing the aircraft to take off.

Remember its true airspeed, not wheel speed like a car.

but the condition is the treadmill moves at the speed of the wheels, not the speed of the plane. So in you description the treadmill would be going 200 mph, not 100 mph.

and the condition of the plane is not that it's moving at 100 mph airspeed, it is at rest..

the condition as stated is impossible...

We know the engines are pushing the plane foreward at a velocity X with reespect to the atmosphere. Therefore on non-moving ground, the wheels would be rotating at X also. Now, instead the ground is now moving at -X also with respect to the air...therefore the wheels are now moving at 2X to the air. Here is the simple fact... As long as the planes wheels are in free motion, they cannot counteract any force being applied to them, either form the plane or the ground, and the forces are merely vecter summed.

 

[Rob9874]

Originally posted by: spidey07

Originally posted by: Rob9874
I had started to post my reasons for thinking the plane will not take off, however, once I started typing, I convinced myself that it would. Here's why. The "won't take off" people are thinking of the wheels as a car's. The car relies on the wheels to move it forward. On an airplane, the wheels are loose, and just there so the belly of the plane doesn't scrape along the runway.

Picture this scenario. Let's say you put your R/C plane on a treadmill, but you are beside the treadmill, with your hand on the plane. If you held the plane steady, the treadmill would be moving and the wheels of the plane would be spinning. But what would happen if you pushed the plane up the treadmill? Do you think that as long as the treadmill kept up with the speed of the wheels, you would not be able to push the plane from the back of the treadmill belt to the front? The wheels would just skid forward on the treadmill belt. That works, because the force pushing it forward (your hand), is not affected by the treadmill moving backwards. That is the same concept of engine thrust. It's an "invisible hand" pushing the airplane forward, independent of the treadmill.

That's the correct thinking.

However it is impossible for the plane to advance given the wording of the scenario. It's a paradox. If the plane advances then it breaks the bounds of the problem.

Which bounds of the problem is that? I think this is where people aren't getting it. Yes, what will happen is the wheels will skid along the moving treadmill, and treat it like a stationary runway.

 

[Linflas]

Originally posted by: spidey07
As stated in the original description it is impossible for the plane to move forward.

No lift = no takeoff.

It will move forward for the same reason that when I screw something to a wall it is pulled against the wall. In the case of an aircraft the wall is the atmosphere and the screw is the propeller. The wheels are meaningless to the problem, they just provide the lowest friction means of allowing the aircraft to move while on solid ground.

 

[Tom]

"The wheels would just skid forward on the treadmill belt. "

you may be correct, but that means the original problem is invalid, not that it's been "solved".

because the original problem does not permit the wheels to "skid".

On the other hand, I think it's possible that the wheels never need to rotate at all, and the treadmill would let the plane move without the wheels ever needing to rotate..

Does that meet the terms of the original problem ?

 

[Zenmervolt]

Originally posted by: spidey07
That's the correct thinking.

However it is impossible for the plane to advance given the wording of the scenario. It's a paradox. If the plane advances then it breaks the bounds of the problem.

The problem is flawed and invalid though. It postulate conditions that are impossible. Logically it's the same as saying, "If Godzilla stomps on a bus, do the people inside survive?"

The only rational way to address the problem is to correct the flawed conditions for what is physically possible and work from there.

ZV

 

[OutHouse]

Originally posted by: Zenmervolt

Originally posted by: Citrix
wrong the props or a jet is not creating lift, its creating forward motion to create wind over the wings as the plane goes faster and faster down the runway and as the air pressure change reaches its magic formula you get lift.

a plane staying in one spot at full power is not moving there is no airpseed and will not take off period.

Firstly, a propellor is a rotating wing. It will pull the airplane forward unless something is anchoring the airplane or physically preventing the airplane's moving forward. A propellor, oriented horizontally, would generate lift. As normall oriented, it provides thrust. However, "lift" and "thrust" are simply directional qualifiers given to the same force. The same principle that causes a wing to generate lift causes a propellor to generate thrust.

Second, unless the axels have absurdly high friction, there is no way that the treadmill could ever generate sufficient friction to counteract the propellor's or jet's thrust.

The plane absolutely will not stay in one spot. It will move forward regardless of treadmill speed.

ZV

you are moving away from the question which is that the treadmill does match the speed of the A/C exactly.

and i retract the prop statement, this subject gets me all fired up and wasnt thinking clearly. I know a prop is a wing that creates thrust which creates forward movement which creates wind which creates airsped and you get lift.

a tredmill matching the exact speed of a plane you would not get lift because the plane is not moving through space its stationary. all you have to do is open the window in the plane and stick your hand out you would feel no wind.

 

[Rob9874]

Originally posted by: Tom
"The wheels would just skid forward on the treadmill belt. "

you may be correct, but that means the original problem is invalid, not that it's been "solved".

because the original problem does not permit the wheels to "skid".

I think this is the fundamental concept we all need to agree on. Because those that think it will move forward, are assuming the wheels will skid.

Think of my R/C plane scenario. Let's assume the treadmill is motorized and moving 100 mph. How am I able to move the plane from the back of the treadmill to the front at 1 mph, even though the treadmill is moving the wheels 100 mph?

 

[OutHouse]

Originally posted by: Zenmervolt

Originally posted by: Citrix

Originally posted by: Rob9874
I had started to post my reasons for thinking the plane will not take off, however, once I started typing, I convinced myself that it would. Here's why. The "will take off" people are thinking of the wheels as a car's. The car relies on the wheels to move it forward. On an airplane, the wheels are loose, and just there so the belly of the plane doesn't scrape along the runway.

Picture this scenario. Let's say you put your R/C plane on a treadmill, but you are beside the treadmill, with your hand on the plane. If you held the plane steady, the treadmill would be moving and the wheels of the plane would be spinning. But what would happen if you pushed the plane up the treadmill? Do you think that as long as the treadmill kept up with the speed of the wheels, you would not be able to push the plane from the back of the treadmill belt to the front? The wheels would just skid forward on the treadmill belt. That works, because the force pushing it forward (your hand), is not affected by the treadmill moving backwards. That is the same concept of engine thrust. It's an "invisible hand" pushing the airplane forward, independent of the treadmill.

plane is still stationary, no wind no lift.

As explained a half-dozen times already, the plane does not remain stationary.

ZV

sorry but i belive it does. how can it move if the treadmill matches the speed of the plane exactly? like running on a treadmill if you set the treadmill to go at 6mph and you run at that speed to stay in the middle of the treadmill tread you are not moving in space you are stationary.

 

[redgtxdi]

Is it me or is this just toooooooooooooooooo freakin' obvious???????



Plane on treadmill = no bernouli's principle = no UPPIES!!!!!!!



WTF is the logic here???


Better would be this:

Plane on a treadmill IN A WIND TUNNEL!!!!


The wings need AIR PASSING OVER THEM TO CREATE LIFT!!!!!