You have a plane and a conveyor belt.

[JujuFish]

Originally posted by: NanoStuff
No I cannot. I could try and explain it again, but I'd rather save it for someone that has the patience to listen and can hold a sensible conversation without resulting to petty insults. But good luck to you, I hope you find the way.

You don't even need to add the "petty insults" part. Although true, you don't even hold a sensible conversation on the matter, since you just like to ignore physics.

 

[NanoStuff]

Originally posted by: JujuFish

Originally posted by: NanoStuff
No I cannot. I could try and explain it again, but I'd rather save it for someone that has the patience to listen and can hold a sensible conversation without resulting to petty insults. But good luck to you, I hope you find the way.

You don't even need to add the "petty insults" part. Although true, you don't even hold a sensible conversation on the matter, since you just like to ignore physics.

Says the man with the fairy-enchanted plane with anti-matter wheels.

 

[cKGunslinger]

Originally posted by: JujuFish

Originally posted by: NanoStuff

Originally posted by: waggy
now the neat thing about this is it does not matter WHAT THE WHEELS ARE DOING (that is the important part).

That is indeed the important part, which makes it particularly unfortunate that you got this part wrong.

I'm literally beginning to feel sorry for you.

Don't, he's just trolling at this point. :thumbsdown:

 

[JujuFish]

Originally posted by: cKGunslinger

Originally posted by: JujuFish

Originally posted by: NanoStuff

Originally posted by: waggy
now the neat thing about this is it does not matter WHAT THE WHEELS ARE DOING (that is the important part).

That is indeed the important part, which makes it particularly unfortunate that you got this part wrong.

I'm literally beginning to feel sorry for you.

Don't, he's just trolling at this point. :thumbsdown:

I'm inclined to agree now.

 

[hellokeith]

Originally posted by: JujuFish
Those who think that a force being applied on the axis of a wheel, and therefore not a torque, is proof that the wheels are not negligible to a plane's acceleration need to take a physics class.

Rolling friction is fairly complicated. The tire and ground surfaces are never perfectly smooth. During motion, the tire compresses and deforms, so that it is no longer circular where it is in contact with the ground surface. The rolling friction is sill mostly pushing backwards, tending to promote the angluar speed. But the redistibution of many Normal forces creates a torque which is negative to the angulare speed and reduces the wheel's forward velocity.

Some other factors to account for are: tire deformation due to the weight of the plane, tire design, inflation of the tire, angle of attack of the undercarriage, axle friction within the wheel rim, temperature of the ground surface, and uniformity of the ground surface.

 

[waggy]

Originally posted by: JujuFish

Originally posted by: cKGunslinger

Originally posted by: JujuFish

Originally posted by: NanoStuff

Originally posted by: waggy
now the neat thing about this is it does not matter WHAT THE WHEELS ARE DOING (that is the important part).

That is indeed the important part, which makes it particularly unfortunate that you got this part wrong.

I'm literally beginning to feel sorry for you.

Don't, he's just trolling at this point. :thumbsdown:

I'm inclined to agree now.

of course he is.
he has been shown proof with physics and all he can say is you are wrong. when asked to show why he just makes a snide little comment.

 

[waggy]

Originally posted by: hellokeith

Originally posted by: JujuFish
Those who think that a force being applied on the axis of a wheel, and therefore not a torque, is proof that the wheels are not negligible to a plane's acceleration need to take a physics class.

Rolling friction is fairly complicated. The tire and ground surfaces are never perfectly smooth. During motion, the tire compresses and deforms, so that it is no longer circular where it is in contact with the ground surface. The rolling friction is sill mostly pushing backwards, tending to promote the angluar speed. But the redistibution of many Normal forces creates a torque which is negative to the angulare speed and reduces the wheel's forward velocity.

Some other factors to account for are: tire deformation due to the weight of the plane, tire design, inflation of the tire, angle of attack of the undercarriage, axle friction within the wheel rim, temperature of the ground surface, and uniformity of the ground surface.

right. but all of those are very very small compared to the thrust generated by the engines.

but you are right they have a slight impact on foreward progress.

 

[Armitage]

Originally posted by: waggy

Originally posted by: hellokeith

Originally posted by: JujuFish
Those who think that a force being applied on the axis of a wheel, and therefore not a torque, is proof that the wheels are not negligible to a plane's acceleration need to take a physics class.

Rolling friction is fairly complicated. The tire and ground surfaces are never perfectly smooth. During motion, the tire compresses and deforms, so that it is no longer circular where it is in contact with the ground surface. The rolling friction is sill mostly pushing backwards, tending to promote the angluar speed. But the redistibution of many Normal forces creates a torque which is negative to the angulare speed and reduces the wheel's forward velocity.

Some other factors to account for are: tire deformation due to the weight of the plane, tire design, inflation of the tire, angle of attack of the undercarriage, axle friction within the wheel rim, temperature of the ground surface, and uniformity of the ground surface.

right. but all of those are very very small compared to the thrust generated by the engines.

but you are right they have a slight impact on foreward progress.

And rolling resistance is nearly independent of velocity. So it takes very little more power to roll the wheels at 140 knots on the conveyor vs. 70 knots on a normal runway.

 

[Suspicious-Teach8788]

Originally posted by: So

Originally posted by: jagec

Originally posted by: So
Show me a conveyor belt that cad do well over 2000kph and I'll show you a great deal on a Bridge in Brooklyn.

I know it would never happen in a real-world situation, but just the fact that it's hypothetically possible weakens our argument.

Not to mention that the 2000kph accounts for ALL the energy in a fully fueled Cessna's tank...How long do they take to burn through that at full throttle? A few hours? Which means that the conveyor WILL be able to keep the plane from taking off for quite a long time, until finally it reaches its top speed and the plane starts coasting down the runway (or the wheels explode). Not to mention I didn't take into account friction losses (works against the Cessna, assuming the belt has a big enough motor).

Of course, the control system for the belt WILL have to be changed from that described in the OP. I suggest a PI control system based on aircraft position.

Therein lies the main point of contention. The OP is proposes an impossible control system. The plane begins to accelerate, so if the belt tries to match it's speed, you get an n = n+1 situation with the speeds raching infinity quickly.

Plus, if we're going into a theoretical world where we have belts that don't exist, why not put magnetic bearings on the wheels of the plane and make friction ~0, putting us back at the original 'the plane will take off' scenario?

You can't reach infinity. You just keep going higher and higher in speeds. The matching is instantaneous, why do people always think matching is 1mph slower? It's instantaneous damnit. Think of a freaking computer that adjusts perfectly and reads the plane so well that it knows how the velocity will change...

 

[Brutuskend]

An airplane taxies in one direction on a moving conveyor belt going the opposite direction. Can the plane take off?
03-Feb-2006


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

Dear Cecil:

Please, please, please settle this question. The discussion has been going on for ages, and any time someone mentions the words "airplane" or "conveyor belt" everyone starts right back up. Here's the original problem essentially as it was posed to us: "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?"

There are some difficulties with the wording of the problem, specifically regarding how we define speed, but the spirit of the situation is clear. The solution is also clear to me (and many others), but a staunch group of unbelievers won't accept it. My conclusion is that the plane does take off. Planes, whether jet or propeller, work by pulling themselves through the air. The rotation of their tires results from this forward movement, and has no bearing on the behavior of a plane during takeoff. I claim the only difference between a regular plane and one on a conveyor belt is that the conveyor belt plane's wheels will spin twice as fast during takeoff. Please, Cecil, show us that it's not only theoretically possible (with frictionless wheels) but it's actually possible too. --Berj A. Doudian, via e-mail

Cecil replies:

Excuse me--did I hear somebody say Monty Hall?

On first encounter this question, which has been showing up all over the Net, seems inane because the answer seems so obvious. However, as with the infamous Monty-Hall-three-doors-and-one-prize-problem (see The Straight Dope: "On Let's Make a Deal" you pick Door #1, 02-Nov-1990), the obvious answer is wrong, and you, Berj, are right--the plane takes off normally, with no need to specify frictionless wheels or any other such foolishness. You're also right that the question is often worded badly, leading to confusion, arguments, etc. In short, we've got a topic screaming for the Straight Dope.

First the obvious-but-wrong answer. The unwary tend to reason by analogy to a car on a conveyor belt--if the conveyor moves backward at the same rate that the car's wheels rotate forward, the net result is that the car remains stationary. An aircraft in the same situation, they figure, would stay planted on the ground, since there'd be no air rushing over the wings to give it lift. But of course cars and planes don't work the same way. A car's wheels are its means of propulsion--they push the road backwards (relatively speaking), and the car moves forward. In contrast, a plane's wheels aren't motorized; their purpose is to reduce friction during takeoff (and add it, by braking, when landing). What gets a plane moving are its propellers or jet turbines, which shove the air backward and thereby impel the plane forward. What the wheels, conveyor belt, etc, are up to is largely irrelevant. Let me repeat: Once the pilot fires up the engines, the plane moves forward at pretty much the usual speed relative to the ground--and more importantly the air--regardless of how fast the conveyor belt is moving backward. This generates lift on the wings, and the plane takes off. All the conveyor belt does is, as you correctly conclude, make the plane's wheels spin madly.

A thought experiment commonly cited in discussions of this question is to imagine you're standing on a health-club treadmill in rollerblades while holding a rope attached to the wall in front of you. The treadmill starts; simultaneously you begin to haul in the rope. Although you'll have to overcome some initial friction tugging you backward, in short order you'll be able to pull yourself forward easily.

As you point out, one problem here is the wording of the question. Your version straightforwardly states that the conveyor moves backward at the same rate that the plane moves forward. If the plane's forward speed is 100 miles per hour, the conveyor rolls 100 MPH backward, and the wheels rotate at 200 MPH. Assuming you've got Indy-car-quality tires and wheel bearings, no problem. However, some versions put matters this way: "The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation." This language leads to a paradox: If the plane moves forward at 5 MPH, then its wheels will do likewise, and the treadmill will go 5 MPH backward. But if the treadmill is going 5 MPH backward, then the wheels are really turning 10 MPH forward. But if the wheels are going 10 MPH forward . . . Soon the foolish have persuaded themselves that the treadmill must operate at infinite speed. Nonsense. The question thus stated asks the impossible -- simply put, that A = A + 5 -- and so cannot be framed in this way. Everything clear now? Maybe not. But believe this: The plane takes off.

LINK

 

[waggy]

Originally posted by: Brutuskend
An airplane taxies in one direction on a moving conveyor belt going the opposite direction. Can the plane take off?
03-Feb-2006


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

Dear Cecil:

Please, please, please settle this question. The discussion has been going on for ages, and any time someone mentions the words "airplane" or "conveyor belt" everyone starts right back up. Here's the original problem essentially as it was posed to us: "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?"

There are some difficulties with the wording of the problem, specifically regarding how we define speed, but the spirit of the situation is clear. The solution is also clear to me (and many others), but a staunch group of unbelievers won't accept it. My conclusion is that the plane does take off. Planes, whether jet or propeller, work by pulling themselves through the air. The rotation of their tires results from this forward movement, and has no bearing on the behavior of a plane during takeoff. I claim the only difference between a regular plane and one on a conveyor belt is that the conveyor belt plane's wheels will spin twice as fast during takeoff. Please, Cecil, show us that it's not only theoretically possible (with frictionless wheels) but it's actually possible too. --Berj A. Doudian, via e-mail

Cecil replies:

Excuse me--did I hear somebody say Monty Hall?

On first encounter this question, which has been showing up all over the Net, seems inane because the answer seems so obvious. However, as with the infamous Monty-Hall-three-doors-and-one-prize-problem (see The Straight Dope: "On Let's Make a Deal" you pick Door #1, 02-Nov-1990), the obvious answer is wrong, and you, Berj, are right--the plane takes off normally, with no need to specify frictionless wheels or any other such foolishness. You're also right that the question is often worded badly, leading to confusion, arguments, etc. In short, we've got a topic screaming for the Straight Dope.

First the obvious-but-wrong answer. The unwary tend to reason by analogy to a car on a conveyor belt--if the conveyor moves backward at the same rate that the car's wheels rotate forward, the net result is that the car remains stationary. An aircraft in the same situation, they figure, would stay planted on the ground, since there'd be no air rushing over the wings to give it lift. But of course cars and planes don't work the same way. A car's wheels are its means of propulsion--they push the road backwards (relatively speaking), and the car moves forward. In contrast, a plane's wheels aren't motorized; their purpose is to reduce friction during takeoff (and add it, by braking, when landing). What gets a plane moving are its propellers or jet turbines, which shove the air backward and thereby impel the plane forward. What the wheels, conveyor belt, etc, are up to is largely irrelevant. Let me repeat: Once the pilot fires up the engines, the plane moves forward at pretty much the usual speed relative to the ground--and more importantly the air--regardless of how fast the conveyor belt is moving backward. This generates lift on the wings, and the plane takes off. All the conveyor belt does is, as you correctly conclude, make the plane's wheels spin madly.

A thought experiment commonly cited in discussions of this question is to imagine you're standing on a health-club treadmill in rollerblades while holding a rope attached to the wall in front of you. The treadmill starts; simultaneously you begin to haul in the rope. Although you'll have to overcome some initial friction tugging you backward, in short order you'll be able to pull yourself forward easily.

As you point out, one problem here is the wording of the question. Your version straightforwardly states that the conveyor moves backward at the same rate that the plane moves forward. If the plane's forward speed is 100 miles per hour, the conveyor rolls 100 MPH backward, and the wheels rotate at 200 MPH. Assuming you've got Indy-car-quality tires and wheel bearings, no problem. However, some versions put matters this way: "The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation." This language leads to a paradox: If the plane moves forward at 5 MPH, then its wheels will do likewise, and the treadmill will go 5 MPH backward. But if the treadmill is going 5 MPH backward, then the wheels are really turning 10 MPH forward. But if the wheels are going 10 MPH forward . . . Soon the foolish have persuaded themselves that the treadmill must operate at infinite speed. Nonsense. The question thus stated asks the impossible -- simply put, that A = A + 5 -- and so cannot be framed in this way. Everything clear now? Maybe not. But believe this: The plane takes off.

LINK

this has been posted like 5 times heh

 

[Brutuskend]

DAMN

I was hoping I was #7

#7 is a good cosmic number, I like #7

 

[cKGunslinger]

Originally posted by: NanoStuff

No I cannot. I could try and explain it again, but I'd rather save it for someone that has the patience to listen and can hold a sensible conversation without resulting to petty insults. But good luck to you, I hope you find the way.

Petty insults? Aren't you the one who responded with this earlier:

If you really are as goddamn old as your avatar suggests, you're a fuckload dumber than me for the age.

Keep denying the fact that you are nothing more than a troll. It's getting funny. :laugh:

 

[NanoStuff]

Yes I did. I have no reason to be nice to a person that has no intention of returning the favor.

 

[PurdueRy]

Originally posted by: NanoStuff
Yes I did. I have no reason to be nice to a person that has no intention of returning the favor.

This is what we call "backpedaling"

 

[NanoStuff]

Originally posted by: PurdueRy

Originally posted by: NanoStuff
Yes I did. I have no reason to be nice to a person that has no intention of returning the favor.

This is what we call "backpedaling"

Some people refer to is as "what goes around comes around"

 

[mugs]

Originally posted by: DLeRium

Originally posted by: So

Originally posted by: jagec

Originally posted by: So
Show me a conveyor belt that cad do well over 2000kph and I'll show you a great deal on a Bridge in Brooklyn.

I know it would never happen in a real-world situation, but just the fact that it's hypothetically possible weakens our argument.

Not to mention that the 2000kph accounts for ALL the energy in a fully fueled Cessna's tank...How long do they take to burn through that at full throttle? A few hours? Which means that the conveyor WILL be able to keep the plane from taking off for quite a long time, until finally it reaches its top speed and the plane starts coasting down the runway (or the wheels explode). Not to mention I didn't take into account friction losses (works against the Cessna, assuming the belt has a big enough motor).

Of course, the control system for the belt WILL have to be changed from that described in the OP. I suggest a PI control system based on aircraft position.

Therein lies the main point of contention. The OP is proposes an impossible control system. The plane begins to accelerate, so if the belt tries to match it's speed, you get an n = n+1 situation with the speeds raching infinity quickly.

Plus, if we're going into a theoretical world where we have belts that don't exist, why not put magnetic bearings on the wheels of the plane and make friction ~0, putting us back at the original 'the plane will take off' scenario?

You can't reach infinity. You just keep going higher and higher in speeds. The matching is instantaneous, why do people always think matching is 1mph slower? It's instantaneous damnit. Think of a freaking computer that adjusts perfectly and reads the plane so well that it knows how the velocity will change...

Listen carefully... the conveyor belt cannot hold the plane in place. Not in this physical world. It can't. So IF the conveyor belt is trying to match the wheel's speed, there WILL be some lag. It is impossible for the conveyor belt to match the speed of the wheel while the plane is moving relative to the ground next to the conveyor belt. In order for the conveyor belt to even BEGIN to move, the plane has to move relative to the ground next to the treadmill, because the plane cannot make its wheels rotate like a car does. So if the treadmill catches up instantaneously, you'll have instantaneous infinite acceleration.

The conveyor belt simply cannot hold the plane in place, not without defying the laws of physics. The situation described in the OP's question is impossible.

 

[GuitarDaddy]

Damn! This thread is still going!

I tried this yesterday. My associates built said conveyor and I took my lear jet over and tried it out. There was a slight bump that spilled my martini, but

THE PLANE TOOK OFF

 

[spidey07]

Originally posted by: mugs
The conveyor belt simply cannot hold the plane in place, not without defying the laws of physics. The situation described in the OP's question is impossible.

Exactly.

And that is why the plane cannot take off.

 

[PurdueRy]

Originally posted by: mugs

Listen carefully... the conveyor belt cannot hold the plane in place. Not in this physical world. It can't. So IF the conveyor belt is trying to match the wheel's speed, there WILL be some lag. It is impossible for the conveyor belt to match the speed of the wheel while the plane is moving relative to the ground next to the conveyor belt. In order for the conveyor belt to even BEGIN to move, the plane has to move relative to the ground next to the treadmill, because the plane cannot make its wheels rotate like a car does. So if the treadmill catches up instantaneously, you'll have instantaneous infinite acceleration.

The conveyor belt simply cannot hold the plane in place, not without defying the laws of physics. The situation described in the OP's question is impossible.

Actually the situation in the OP is fine. As he said "The speed the wheels move FORWARD" This direction implies linear speed. It was when he added a follow up post of his own incorrect interpretation that all this confusion came about. The question is if the treadmill matched the forward speed of the aircraft....that is all. The OP agreed this situation causes takeoff. Therefore the answer is YES

 

[PurdueRy]

Originally posted by: spidey07

Originally posted by: mugs
The conveyor belt simply cannot hold the plane in place, not without defying the laws of physics. The situation described in the OP's question is impossible.

Exactly.

And that is why the plane cannot take off.

Yet another one of your TYPICAL posts in this thread. Wait for someone to say something, agree with them, and say nothing in regards to physics.

See my post above, answer the REAL question, and then move on.

 

[EyeMWing]

The plane takes off if you ignore the physics-defying stipulations of the OP, which mandate that the plane DOES NOT take off.

I hereby propose that we hand the Mythbusters a Cessna 152 and laugh as they build a runway-sized treadmill, and smash the plane 3 times before achieving flight.

 

[NanoStuff]

Originally posted by: mugs

Originally posted by: DLeRium

Originally posted by: So

Originally posted by: jagec

Originally posted by: So
Show me a conveyor belt that cad do well over 2000kph and I'll show you a great deal on a Bridge in Brooklyn.

I know it would never happen in a real-world situation, but just the fact that it's hypothetically possible weakens our argument.

Not to mention that the 2000kph accounts for ALL the energy in a fully fueled Cessna's tank...How long do they take to burn through that at full throttle? A few hours? Which means that the conveyor WILL be able to keep the plane from taking off for quite a long time, until finally it reaches its top speed and the plane starts coasting down the runway (or the wheels explode). Not to mention I didn't take into account friction losses (works against the Cessna, assuming the belt has a big enough motor).

Of course, the control system for the belt WILL have to be changed from that described in the OP. I suggest a PI control system based on aircraft position.

Therein lies the main point of contention. The OP is proposes an impossible control system. The plane begins to accelerate, so if the belt tries to match it's speed, you get an n = n+1 situation with the speeds raching infinity quickly.

Plus, if we're going into a theoretical world where we have belts that don't exist, why not put magnetic bearings on the wheels of the plane and make friction ~0, putting us back at the original 'the plane will take off' scenario?

You can't reach infinity. You just keep going higher and higher in speeds. The matching is instantaneous, why do people always think matching is 1mph slower? It's instantaneous damnit. Think of a freaking computer that adjusts perfectly and reads the plane so well that it knows how the velocity will change...

Listen carefully... the conveyor belt cannot hold the plane in place. Not in this physical world. It can't. So IF the conveyor belt is trying to match the wheel's speed, there WILL be some lag. It is impossible for the conveyor belt to match the speed of the wheel while the plane is moving relative to the ground next to the conveyor belt. In order for the conveyor belt to even BEGIN to move, the plane has to move relative to the ground next to the treadmill, because the plane cannot make its wheels rotate like a car does. So if the treadmill catches up instantaneously, you'll have instantaneous infinite acceleration.

The conveyor belt simply cannot hold the plane in place, not without defying the laws of physics. The situation described in the OP's question is impossible.

The question in the OP is very possible. The correct interpretation is infact FORWARD, as in 'linear speed' of the wheel, rather than rotation.

My intention was to imply wheel rotation to add a twist to the original question... I must have missed that bit so that just brings us back to the original question, in which case the plane will take off, even though people seem to disagree as to how easy it would be for the plane to take off.

As for infinite acceleration for the alternate scenario, I don't agree with that, but perhaps that's another story.

 

[PurdueRy]

Originally posted by: NanoStuff

Originally posted by: mugs

Originally posted by: DLeRium

Originally posted by: So

Originally posted by: jagec

Originally posted by: So
Show me a conveyor belt that cad do well over 2000kph and I'll show you a great deal on a Bridge in Brooklyn.

I know it would never happen in a real-world situation, but just the fact that it's hypothetically possible weakens our argument.

Not to mention that the 2000kph accounts for ALL the energy in a fully fueled Cessna's tank...How long do they take to burn through that at full throttle? A few hours? Which means that the conveyor WILL be able to keep the plane from taking off for quite a long time, until finally it reaches its top speed and the plane starts coasting down the runway (or the wheels explode). Not to mention I didn't take into account friction losses (works against the Cessna, assuming the belt has a big enough motor).

Of course, the control system for the belt WILL have to be changed from that described in the OP. I suggest a PI control system based on aircraft position.

Therein lies the main point of contention. The OP is proposes an impossible control system. The plane begins to accelerate, so if the belt tries to match it's speed, you get an n = n+1 situation with the speeds raching infinity quickly.

Plus, if we're going into a theoretical world where we have belts that don't exist, why not put magnetic bearings on the wheels of the plane and make friction ~0, putting us back at the original 'the plane will take off' scenario?

You can't reach infinity. You just keep going higher and higher in speeds. The matching is instantaneous, why do people always think matching is 1mph slower? It's instantaneous damnit. Think of a freaking computer that adjusts perfectly and reads the plane so well that it knows how the velocity will change...

Listen carefully... the conveyor belt cannot hold the plane in place. Not in this physical world. It can't. So IF the conveyor belt is trying to match the wheel's speed, there WILL be some lag. It is impossible for the conveyor belt to match the speed of the wheel while the plane is moving relative to the ground next to the conveyor belt. In order for the conveyor belt to even BEGIN to move, the plane has to move relative to the ground next to the treadmill, because the plane cannot make its wheels rotate like a car does. So if the treadmill catches up instantaneously, you'll have instantaneous infinite acceleration.

The conveyor belt simply cannot hold the plane in place, not without defying the laws of physics. The situation described in the OP's question is impossible.

The question in the OP is very possible. The correct interpretation is infact FORWARD, as in 'linear speed' of the wheel, rather than rotation.

My intention was to imply wheel rotation to add a twist to the original question... I must have missed that bit so that just brings us back to the original question, in which case the plane will take off, even though people seem to disagree as to how easy it would be for the plane to take off.

As for infinite acceleration for the alternate scenario, I don't agree with that, but perhaps that's another story.

Thank you dude. :thumbsup:

I agree with everything you said. No more semantics.

 

[mugs]

Originally posted by: PurdueRy

Originally posted by: mugs

Listen carefully... the conveyor belt cannot hold the plane in place. Not in this physical world. It can't. So IF the conveyor belt is trying to match the wheel's speed, there WILL be some lag. It is impossible for the conveyor belt to match the speed of the wheel while the plane is moving relative to the ground next to the conveyor belt. In order for the conveyor belt to even BEGIN to move, the plane has to move relative to the ground next to the treadmill, because the plane cannot make its wheels rotate like a car does. So if the treadmill catches up instantaneously, you'll have instantaneous infinite acceleration.

The conveyor belt simply cannot hold the plane in place, not without defying the laws of physics. The situation described in the OP's question is impossible.

Actually the situation in the OP is fine. As he said "The speed the wheels move FORWARD" This direction implies linear speed. It was when he added a follow up post of his own incorrect interpretation that all this confusion came about. The question is if the treadmill matched the forward speed of the aircraft....that is all. The OP agreed this situation causes takeoff. Therefore the answer is YES

He phrased it two different ways in the OP. No wonder people are discussing two different questions.

Version 1:

The belt compensates for the rotation of the wheels in reverse

Version 2:

as in the belt moves in reverse exactly as fast as the wheels move forward.

Those mean the opposite.

At least we can all agree that DLeRium is a pompous ass.