Will the plane take off?

[KSXNSX]

It conserves. The thread mill doesnt run on free will.

:biggrin:

 

[KSXNSX]

I will rent the plane and get a treadmill. I think if we put you up in a Hoilday Inn Express the night before we should be A.O.K.:wink:

:biggrin:

 

[KSXNSX]

This was absolutely NOT the point of the question. The point was for YOU to figure out if given the scenario, would the plane move or not. It was not telling you the plane was stationary, it was not telling you it would move. It's up to you to SOLVE that given the data. THAT was the entire point of the question and once you solve that, THEN you have the answer. Way too many have jumped to the conclusion that if the treadmill speed matched the plane speed, then it would be stationary. That is not an assumption, that's an incorrect answer to the question.

If I solve the QUESTION then what would that LEAVE pretentious PEOPLE to do with THEIR spare time?


:biggrin:

 

[Vega$ NSX]

Again, this should help visualize the problem. If any of you still feel the need to be convinced, take your car to get dyno'd. Let me know how much wind burn you get from loading the engine up.

Or if you still concede that the plane moves forward relative to the ground--that is fine by me. That's certainly a valid assumption to be made. So it moves forward--how is this a difficult question and how do you know if you can take off without knowing at what speed the plane is traveling relative to the ground, how heavy the plane is how far the plane travels etc? Those parameters aren't given because that wasn't the point of the poorly-worded question and if they were it seems like it would be just like any other takeoff.

Again, this is NOT a car. That is the source of yours any many other's confusion. A car uses it's wheels to generate forward movement. It needs a friction force between the contact of the wheels to the ground/pavement/treadmill/dyno in order to move forward. That is why a car will move forward only as fast as the tires will hold forces. It is no different then if you put a car on ice. When there is no friction between the tires and the ice, the car goes nowhere.

That is NOT the case with a plane. The plane uses thrust from an engine to move forward. It does not use the wheels. So if you put a plane on that same piece of ice, it WILL move forward, while the car will not. Put a plane and a car in space. Give the car 1,000,000 whp and floor it. Will it move? No. Give the plane 10 hp of thrust. Will it move. Yes.

They are not the same and if you can't understand why then you will not be able to see why a plane can move forward on a treadmill. It is the same reason a plane can move foward in space and a car can't.

 

[Aero]

I hope you mean space like within the atmosphere and not outer space. :wink:

What if its one of these?

http://www.aerocar.com/

 

[KSXNSX]

Again, this is NOT a car. That is the source of yours any many other's confusion. A car uses it's wheels to generate forward movement. It needs a friction force between the contact of the wheels to the ground/pavement/treadmill/dyno in order to move forward. That is why a car will move forward only as fast as the tires will hold forces. It is no different then if you put a car on ice. When there is no friction between the tires and the ice, the car goes nowhere.

That is NOT the case with a plane. The plane uses thrust from an engine to move forward. It does not use the wheels. So if you put a plane on that same piece of ice, it WILL move forward, while the car will not. Put a plane and a car in space. Give the car 1,000,000 whp and floor it. Will it move? No. Give the plane 10 hp of thrust. Will it move. Yes.

They are not the same and if you can't understand why then you will not be able to see why a plane can move forward on a treadmill. It is the same reason a plane can move foward in space and a car can't.

I totally agree with your point--I never disagreed with it. All I am saying is no matter what, according to the scenario you are going to have to make one of two assumptions. I already explained this previously. The plane moves relative to the ground. The plane doesn't move relative to the ground. In the former scenario, the plane may be able to take off. In the latter, it is impossible.

If the plane is able to move forward relative to the ground, I really don't see much point to the riddle at all--futhermore, it would be impossible to answer the ultimate question of whether or not it would be able to take off without more data.

If you are going to assume that everything below the fuselage of the plane is frictionless, then why even include the treadmill? Why go to the trouble of explaining that the belt tracks the planes speed and runs in the opposite direction at an equal speed? If it is frictionless, then all of that is immaterial. If everything was frictionless, and I started the belt, the plane would just sit there. Then I turn on the engines and the plane moves forward. What is the point of the riddle? Isn't everything quite obvious? If it isn't frictionless, then you can't come to an answer without more information.

Personally, I think the problem was meant to imply the plane remained stationary relative to the ground (i.e. to test the reader's knowledge of lift and fluid dynamics--how a plane flies). The question requires an assumption, and depending on which assumption you make, you will either be able to answer the question definitively or not.

You assume the plane is static relative to the ground: your answer is definitive--the plane does not take off

You assume the plane can move relative to the ground: the plane may be able to take off, but you'd have to know more before you could say for sure. You'd have to achieve the same speed relative to the ground as the least amount of speed needed for a nominal take-off. If the plane can move forward, what's the point of the set-up? It seems like the answer--or lack thereof--is obvious.

 

[Vega$ NSX]

I'm pretty sure my last post sums it up. You either believe the plane moves or the plane doesn't--relative to the ground. There are no other options. The list is exclusive and exhaustive.

If the plane doesn't move relative to the ground, it won't take off. Argue whatever you want--you are going to be wrong.

If you believe it moves, fine. Then it takes off if it reaches a certain speed/distance just like any other normal takeoff. Why bother with the question and the elaborate--yet vague--set up? There is no point to the treadmill if you are going to let the plane move forward any distance relative to the ground. You may as well say something like: you cut the engines to X% of the normal output used in a nominal takeoff; you cut the distance allowed for takeoff by X%.

The problem is that you are thinking about distance displaced by the plane relative to the runway it is on. Normally, this is the ground. In the question, it is the belt of the treadmill. You need to be thinking about the plane relative to the surrounding air. Once you understand how we are able to fly, the solution becomes obvious. Again, we are talking about a normal passenger airplane--not a harrier or some kind of jet with thrust vectoring.

You could put wings on a treadmill, and if you passed enough air over and under the wings the treadmill will takeoff. That'd be a funner scenario. Or an NSX. That'd be better.

The question is worded correctly. All it says is that the treadmill moves backwards at the same rate the plane moves forward. It specifically does not state that the plane does not move forward. That is it's intention because allows the reader to make the incorrect assumption that the plane will not move either. This question was originally dubbed as a "brain teaser" and that is the point of a brain teaser. It gives you enough information to lead you to a common misunderstanding so that the average person who doesn't really think about the question falls for it.

Example:

There is a red house, blue house and white house. The red house is located to the left of the blue house. The blue house is in the middle. Where is the white house located?

Now the common person would make assumptions. Maybe it's on the left, maybe it's on the right. Or maybe they will claim there is not enough information provided to answer the question. However, they have fallen for the brain teaser because they are making assumptions. They are assuming that the "white house" has anything to do with the red or blue house. If you were just asked the question, "where is the white house?" you would easily reply with the correct answer of "Washington DC". However, it is all the verbiage above that let the reader make their own incorrect assumptions and clouding their mind from the correct answer.

So in the plane and treadmill question, all of the talk of a treadmill moving backwards at the speed of the plane moving forward is to cloud the reader into thinking the movement of the treadmill has anything to do with the movement of the plane. The simple answer is that for the most part (aside from frictional forces etc.) it does not. The wheels are free spinning so it does not matter what is spinning underneath the plane because it is the force of the engine that is moving the plane forward, not the wheels. If the question clearly stated "the plane does not move" then what is the point of the treadmill? If we know the plane can not move, what difference does it make what method is used to immobilize the plane. Why not say it's bolted to the ground or attached to an anchor? The question HAS to leave the plane's movement ambiguous because anyone knows that a plane that does not move cannot fly.

As for your argument of relative velocities, it is a moot point. What we are claiming is that the plane will move forward relative to the ground. Since the treadmill is on the ground it is also considered ground, in that it is the fixed stationary point. Velocity is defined as movement of an object relative to or from a fixed stationary point. We’ve explained over and over again that the plane can move forward relative to that fixed stationary point. If we assume that wind velocity is zero, it too is considered ground because it too is not moving relative to ground (a fixed stationary point). Which is a reasonable assumption because if the wind velocity was moving fast enough towards or away from the plane, then it would make the point of the treadmill moot; the plane would either never take off or just take off without having to move at all. So if the wind velocity is zero, and the plane moves through it with velocity, then fluid dynamics take over and lift is generated.

 

[Vega$ NSX]

I hope you mean space like within the atmosphere and not outer space. :wink:

Actually I was talking about Inner Space, that craptacular movie starring Martin Short. :tongue:

 

[Vega$ NSX]

You might want to re-think this question. The engines are operating nominally--combustion is nominal, output is nominal. I don't understand why you would think there is a problem with conservation of energy. Explain why you think this law is being violated and I think you'll find the solution to your own question.

What he is talking about is what I've detailed in my post earlier.

Newtons Laws are simple. If you do not put any forces on an object it doesn't move. If you put a force on an object it moves. However, if you put a force on an object and then apply an equal and opposite reactive force, then the object will not move because the net balance of forces equals zero.

Example: If we jump out of a plane, we fall relative to the ground. Why? Becuase that is the force of gravity pushing down on us (hence, put a force on an object it moves). So when we are standing on the ground, aren't we still feeling the force of gravity? Then why are we free falling past the ground into the center of the earth? That is because the earth is pushing back up on us with an equal force. The net balance is zero and thus we don't move anywhere.

SO in the example of the plane I drew a free body diagram, which in dynamics shows ALL of the forces acting on an object. If the net balance of the forces is zero, then the plane does not move. However, in my example I show that the plane has about 192,000 ft-lbs of force moving the plane forward. In order the plane to remain stationary (as you are claiming), there needs to be an equal force of 192,000 ft-lbs of force pushing right back against the force of the engine to keep the plane from moving (there needs to be a net zero balance of forces). However, I showed that the force pushing back on the plane (rolling resistance) is only about 32,000 ft-lbs. That means the net balance is of the forces is about 160,000 ft-lbs of force pushing the plane forward. Therefore it moves and will fly. This is all relative to ground (as stated above).

 

[Vega$ NSX]

And almost all airplanes take off in a range of about 50-130kts.

Excellent! Now we can solve this problem. You probably have the resources to do this. If we assume that the plane to be travelling at about 100 kts. at the point of takeoff, then we know the treadmill is moving backwards at 100 kts. Correct? That would have to mean the wheels are spinning as if the plane were travelling at 200 kts, right? Look up what the rolling resistance force is at 200 kts, and I guarantee you it will be less than the force of the plane thrusters moving forward. If the plane can overcome the rolling resistance of the wheels at 200 kts, then we know the plane must fly.

 

[JoeSchmoe]

What he is talking about is what I've detailed in my post earlier.

Newtons Laws are simple. If you do not put any forces on an object it doesn't move. If you put a force on an object it moves. However, if you put a force on an object and then apply an equal and opposite reactive force, then the object will not move because the net balance of forces equals zero.

Example: If we jump out of a plane, we fall relative to the ground. Why? Becuase that is the force of gravity pushing down on us (hence, put a force on an object it moves). So when we are standing on the ground, aren't we still feeling the force of gravity? Then why are we free falling past the ground into the center of the earth? That is because the earth is pushing back up on us with an equal force. The net balance is zero and thus we don't move anywhere.

SO in the example of the plane I drew a free body diagram, which in dynamics shows ALL of the forces acting on an object. If the net balance of the forces is zero, then the plane does not move. However, in my example I show that the plane has about 192,000 ft-lbs of force moving the plane forward. In order the plane to remain stationary (as you are claiming), there needs to be an equal force of 192,000 ft-lbs of force pushing right back against the force of the engine to keep the plane from moving (there needs to be a net zero balance of forces). However, I showed that the force pushing back on the plane (rolling resistance) is only about 32,000 ft-lbs. That means the net balance is of the forces is about 160,000 ft-lbs of force pushing the plane forward. Therefore it moves and will fly. This is all relative to ground (as stated above).


Excellent! Now we can solve this problem. You probably have the resources to do this. If we assume that the plane to be travelling at about 100 kts. at the point of takeoff, then we know the treadmill is moving backwards at 100 kts. Correct? That would have to mean the wheels are spinning as if the plane were travelling at 200 kts, right? Look up what the rolling resistance force is at 200 kts, and I guarantee you it will be less than the force of the plane thrusters moving forward. If the plane can overcome the rolling resistance of the wheels at 200 kts, then we know the plane must fly.

We need to add this to the wiki.

-- Joe

 

[KSXNSX]

The question is worded correctly. All it says is that the treadmill moves backwards at the same rate the plane moves forward. It specifically does not state that the plane does not move forward. That is it's intention because allows the reader to make the incorrect assumption that the plane will not move either. This question was originally dubbed as a "brain teaser" and that is the point of a brain teaser. It gives you enough information to lead you to a common misunderstanding so that the average person who doesn't really think about the question falls for it.

Example:

There is a red house, blue house and white house. The red house is located to the left of the blue house. The blue house is in the middle. Where is the white house located?

Now the common person would make assumptions. Maybe it's on the left, maybe it's on the right. Or maybe they will claim there is not enough information provided to answer the question. However, they have fallen for the brain teaser because they are making assumptions. They are assuming that the "white house" has anything to do with the red or blue house. If you were just asked the question, "where is the white house?" you would easily reply with the correct answer of "Washington DC". However, it is all the verbiage above that let the reader make their own incorrect assumptions and clouding their mind from the correct answer.

So in the plane and treadmill question, all of the talk of a treadmill moving backwards at the speed of the plane moving forward is to cloud the reader into thinking the movement of the treadmill has anything to do with the movement of the plane. The simple answer is that for the most part (aside from frictional forces etc.) it does not. The wheels are free spinning so it does not matter what is spinning underneath the plane because it is the force of the engine that is moving the plane forward, not the wheels. If the question clearly stated "the plane does not move" then what is the point of the treadmill? If we know the plane can not move, what difference does it make what method is used to immobilize the plane. Why not say it's bolted to the ground or attached to an anchor? The question HAS to leave the plane's movement ambiguous because anyone knows that a plane that does not move cannot fly.

As for your argument of relative velocities, it is a moot point. What we are claiming is that the plane will move forward relative to the ground. Since the treadmill is on the ground it is also considered ground, in that it is the fixed stationary point. Velocity is defined as movement of an object relative to or from a fixed stationary point. We’ve explained over and over again that the plane can move forward relative to that fixed stationary point. If we assume that wind velocity is zero, it too is considered ground because it too is not moving relative to ground (a fixed stationary point). Which is a reasonable assumption because if the wind velocity was moving fast enough towards or away from the plane, then it would make the point of the treadmill moot; the plane would either never take off or just take off without having to move at all. So if the wind velocity is zero, and the plane moves through it with velocity, then fluid dynamics take over and lift is generated.

No the question is not worded sufficiently--if you think it is, then there is nothing else I can say. I already provided all the possible outcomes, and not one of your arguments or conclusions disagree with mine. I said if the plane is moving forward relative to the ground, it is possible that it will take off--but you need to have more information. I don't see what the disagreement is about besides you are absolutely sure the author's wording is sufficient and that he intended for the plane to be able to move forward relative to the ground (i.e. he didn't meant for the plane to be stationary and just worded everything so poorly that it turned out he accomplished the exact opposite). You seem to think that it is impossible the plane remains stationary relative to the ground. Tell me, if the plane is put on a treadmill and it remains still relative to the ground, what is its speed? 0 Now, the conveyor belt tracks the speed of the plane, and matches it in an opposite direction. What is its speed? 0. No problems thus far right? Is the plane taking off? Nope. What is the problem here? You are assuming the plane is moving at a nominal speed the instant we start the observation of this experiment. Did he tell us if the plane moved from a static start or a rolling start? Nope. Was the author's question sufficient? Nope.

now lets clear some things up, before we move on, I think we should clear up speed and velocity. Velocity is speed with a direction. So let's arbitrarily say the plane's nose faces to the right and the conveyor belt moves to the left.

OK. So we move up to 1 m/s (or 1 mph if you are more comfortable with that). The plane moves 1 m/s to the right. oh wait, 1 m/s relative to what? to the conveyor belt or to the ground? Either way, the plane is moving right? If you are already giving the plane movement by giving it a speed, then isn't it a given that it is already moving? Why set up the whole conveyor belt that tracks its speed and matches it in the opposite direction? If the plane is able to move, then isn't it obvious that it will be able to fly as I already proposed? Eventually 1 will get up to the minimum speed necessary for take-off.

My personal opinion is that the author of the riddle is a complete moron, and anyone that thinks that the details provided in the question are sufficient to answer it without making any assumptions won't listen to reason.

I think what you keep focusing on, along with several others, is if the plane will move forward relative to the earth--or the conveyor belt. If the plane has a speed/velocity, then wouldn't it necessarily have to be moving forward? What problem did you exactly solve? None. Can the plane take off? Of course. What was the point of the "riddle"?

I covered all possible scenarios and laid out the possible outcomes for those scenarios. So I really don't see how we can be at disagreement except for the fact that you believe the set-up to be sufficient. Go ahead is my opinion. We could be here for years. You focus on if the plane will move forward or not--although it's already a given if the plane has been given a velocity--and I'll focus on lift.

 

[THE STIG]

If we jump out of a plane, we fall relative to the ground.

I don't believe it.

 

[Deltron Zero]

KSXNSX. I still don't understand what you think keeps the plane from moving forward. Do you think the treadmill keeps the plane from moving forward. It's like your skipping that whole step.

 

[KSXNSX]

KSXNSX. I still don't understand what you think keeps the plane from moving forward. Do you think the treadmill keeps the plane from moving forward. It's like your skipping that whole step.

If you actually read what I stated 5 times or so, you would have the answer.

My first post stated you have to make an assumption of what the author actually intends in the hypothetical situation. If the plane is motionless relative to the ground, then there is no take-off because there is no lift.

If it moves, then of course it can take off if you reach a certain speed.

Personally, I think the author intended for the plane to be stationary--hence describing the belt matching the speed of the wheels in the exact opposite direction. Of course, by wording it this way he accomplished the exact opposite. If you interpret it as stated, then yes the plane takes off as I mentioned because the plane moves forward--but then it wouldn't be much of a brain teaser would it?

 

[Deltron Zero]

If you actually read what I stated 5 times or so, you would have the answer.

My first post stated you have to make an assumption of what the author actually intends in the hypothetical situation. If the plane is motionless relative to the ground, then there is no take-off because there is no lift.

If it moves, then of course it can take off if you reach a certain speed.

Personally, I think the author intended for the plane to be stationary--hence describing the belt matching the speed of the wheels in the exact opposite direction. If you interpret it as stated, then yes the plane takes off as I mentioned because the plane moves forward--but then it wouldn't be much of a brain teaser would it?

Okay. Let me rephrase the question. Why are you assuming the plane is not moving forward?

Just because you think the author was a moron and used a treadmill instead of anchor or any other device that would keep the plane from moving forward? If so, then I really don't think it would be much of a riddle.

Your interpretation of the riddle is like asking "will the plane fly if it cannot move." Real brain teaser there!!!

 

[Vega$ NSX]

No the question is not worded sufficiently--if you think it is, then there is nothing else I can say. I already provided all the possible outcomes, and not one of your arguments or conclusions disagree with mine.

No, because there is only 1 possible outcome. There is no outcome where the plane cannot gain velocity and remains stationary.

You seem to think that it is impossible the plane remains stationary relative to the ground.

No, I'm saying if the plane applies a thrust, the force of the treadmill is not sufficient to keep the plane from moving.

Tell me, if the plane is put on a treadmill and it remains still relative to the ground, what is its speed? 0 Now, the conveyor belt tracks the speed of the plane, and matches it in an opposite direction. What is its speed? 0. No problems thus far right? Is the plane taking off? Nope. What is the problem here? You are assuming the plane is moving at a nominal speed the instant we start the observation of this experiment. Did he tell us if the plane moved from a static start or a rolling start? Nope. Was the author's question sufficient? Nope.

This would all be fine and dandy if the authors question was "Is the plane currently taking off or not?" You are assuming only a fixed situation given a specific time. But that was NOT the author's question. The author's question was "CAN the plane take off?" Meaning does the plane have the capability to take off regardless if the plane starts off stationary or moving. If we enter the scene where the plane is stationary, CAN the plane take off. The answer is still yes, even though the velocity is 0. It is not asking IS the plane taking off, it is asking CAN the plane take off. There is a big difference between the two. The question is independent of time or what the plane is currently doing.

now lets clear some things up, before we move on, I think we should clear up speed and velocity. Velocity is speed with a direction. So let's arbitrarily say the plane's nose faces to the right and the conveyor belt moves to the left.

OK. So we move up to 1 m/s (or 1 mph if you are more comfortable with that). The plane moves 1 m/s to the right. oh wait, 1 m/s relative to what? to the conveyor belt or to the ground?

Both. The conveyor belt IS the ground. The plane moves forward relative to both. But more importantly it moves relative to the air surrounding it too. And it is that movemet that allows the wings of the plane to create lift.

Either way, the plane is moving right? If you are already giving the plane movement by giving it a speed, then isn't it a given that it is already moving? Why set up the whole conveyor belt that tracks its speed and matches it in the opposite direction? If the plane is able to move, then isn't it obvious that it will be able to fly as I already proposed? Eventually 1 will get up to the minimum speed necessary for take-off.

No the plane doesn't have to start off moving. It can start off stationary. And many people believe that once the plane is stationary that it CANNOT move. They believe that any forward motion is counteracted by the treadmill spinning backwards, like a car on a dyno. The wheels move, the threadmill moves but the plane moves nowhere relative to the ground. In this case, people think that the plane will not gain any speed, it will just spin it's wheels while remaining stationary. That is because they confuse how a plane generates speed as compared to a car.

My personal opinion is that the author of the riddle is a complete moron, and anyone that thinks that the details provided in the question are sufficient to answer it without making any assumptions won't listen to reason.

I would have to disagree on both counts.

I think what you keep focusing on, along with several others, is if the plane will move forward relative to the earth--or the conveyor belt. If the plane has a speed/velocity, then wouldn't it necessarily have to be moving forward?

Yes, but that's the big "IF" in question. That is the basis of the entire debate. People have been arguing that the plane will not move forward, even if the plane is thrusting at full force. We are trying to explain to them that the plane will move forward relative to the earth/belt.

What problem did you exactly solve? None. Can the plane take off? Of course. What was the point of the "riddle"?

Again, the point of the riddle is to confuse people about how planes and cars achive speed/velocity. A car on a treadmill would not gain speed or velocity because the spinning of the wheels would be counteracted by the treadmill. The wheels would spin and the treadmill would spin the other way and the car will not have moved relative to the ground or treadmill (i.e. it is not moving further away from the treadmill then when it started). A plane is different. When it thrusts, it can move on the treadmill because the force is not generated at the wheels. Thus, it will generate velocity/speed (it will start to move away from the treadmill). People try to apply the car logic to the plane, and thus the point of the riddle.

 

[KSXNSX]

Okay. Let me rephrase the question. Why are you assuming the plane is not moving forward?

Just because you think the author was a moron and used a treadmill instead of anchor or any other device that would keep the plane from moving forward? If so, then I really don't think it would be much of a riddle.

Your interpretation of the riddle is like asking "will the plane fly if it cannot move." Real brain teaser there!!!

And your interpretation of the riddle is like asking "will the plane fly if it moves?" Real brain teaser there!!!

:biggrin:

I love it when ppl get upset over this riddle. Keep me updated. Read my first post and you know where I stand.

http://www.nsxprime.com/forums/showpost.php?p=916394&postcount=172

 

[sahtt]

If you actually read what I stated 5 times or so, you would have the answer.

My first post stated you have to make an assumption of what the author actually intends in the hypothetical situation. If the plane is motionless relative to the ground, then there is no take-off because there is no lift.

If it moves, then of course it can take off if you reach a certain speed.

Personally, I think the author intended for the plane to be stationary--hence describing the belt matching the speed of the wheels in the exact opposite direction. Of course, by wording it this way he accomplished the exact opposite. If you interpret it as stated, then yes the plane takes off as I mentioned because the plane moves forward--but then it wouldn't be much of a brain teaser would it?

I can't really consider your answer as anything besides incorrect. Your emphasis on the ground, "minor air flow", molecules, etc. has no bearing on the question IMO. I'm not saying they are completely "wrong" from every possible point of view, but the question is worded exactly to provoke the uncertainty you've demonstrated, once again IMO. I also originally asked this question in a different thread.

 

[KSXNSX]

Frankly, I don't care. I tried to point out that the question is flawed and depending on how you interpret it, you have two possible outcomes. I personally interpret the question one way, and you interpret it the other.

Yet you are the only ones insisting on a definitive answer with the information provided--and I can say incontrovertibly that you need more information to answer the question of if the plane will take off or not.

If you read my posts, I doubt we'll have any point of contention. If not--which is what most ppl seem to favor--then enjoy.

 

[Vega$ NSX]

Personally, I think the author intended for the plane to be stationary--hence describing the belt matching the speed of the wheels in the exact opposite direction.

This is the entire point of this arguement. You, along with so many others, think that the belt of the treadmill has any effect on keeping the plane from moving. In other words, a treadmill cannot keep a plane stationary in reference to any point. It can keep a car stationary, but not a plane.


Also note, the question does not say the belt matches the speed of the wheels, it says it matches the speed of the plane. That means the plane can be moving at 100 mph, the belt moves at 100 mph and the wheels travel at 200 mph. The plane still moves forward 100 mph. The belt matching the speed of the plane does not equate to stationary plane.

 

[KSXNSX]

This is the entire point of this arguement. You, along with so many others, think that the belt of the treadmill has any effect on keeping the plane from moving. In other words, a treadmill cannot keep a plane stationary in reference to any point. It can keep a car stationary, but not a plane.


Also note, the question does not say the belt matches the speed of the wheels, it says it matches the speed of the plane. That means the plane can be moving at 100 mph, the belt moves at 100 mph and the wheels travel at 200 mph. The plane still moves forward 100 mph. The belt matching the speed of the plane does not equate to stationary plane.

Do you even read my posts or do you just skim over them?

1. "Imagine a plane is sitting on a massive conveyor belt, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation.

Can the plane take off?"

http://boards.straightdope.com/sdmb/showthread.php?t=348452

I had to look up the question because it is so old

2. Please peruse my posts at your leisure. I am sure there will be no source of debate if you actually take the time.

3. Fine, the plane is moving at 100 mph. What exactly is the riddle? You already said the plane was moving. That's an assumption you made. The plane moves--> the plane can fly if it reaches whatever speed it needs to take-off.

Done? I know I am.

 

[Vega$ NSX]

I tried to point out that the question is flawed and depending on how you interpret it, you have two possible outcomes. I personally interpret the question one way, and you interpret it the other.

Yet you are the only ones insisting on a definitive answer with the information provided.

That is because one of your intepretations uses flawed logic, thus one of your outcomes is incorrect, thus is not a possible outcome. The treadmill cannot keep the plane stationary. There are no means by which it can keep the plane from moving. Just because the treadmill spins, no matter how fast, it does not mean the plane cannot move. That is why your interpretation is wrong because it is based on the belief that the movement of the treadmill can keep the plane stationary. It cannot. Read all of the prevous posts to see why the treadmill is not capable of this.

 

[KSXNSX]

That is because one of your intepretations uses flawed logic, thus one of your outcomes is incorrect, thus is not a possible outcome. The treadmill cannot keep the plane stationary. There are no means by which it can keep the plane from moving. Just because the treadmill spins, no matter how fast, it does not mean the plane cannot move. That is why your interpretation is wrong because it is based on the belief that the movement of the treadmill can keep the plane stationary. It cannot. Read all of the prevous posts to see why the treadmill is not capable of this.

Oh gawd, see previous post (i.e. read). Actually, read + comprehend. I don't know how many unsubstantiated assumptions you have made, but even I have to admit this discussion is getting less and less fun/interesting each time you put words in my mouth.

I said I believe the author intended for the plane to remain stationary, no matter how poorly he set up the problem.

And to say that it is impossible for the treadmill to keep the plane stationary...really? Everything else seems possible to you huh? It's almost comical that you have a definitive answer to a question that is impossible to answer based only on the information given.

 

[Vega$ NSX]

Do you even read my posts or do you just skim over them?

1. "Imagine a plane is sitting on a massive conveyor belt, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation.

Can the plane take off?"

http://boards.straightdope.com/sdmb/showthread.php?t=348452

I had to look up the question because it is so old

2. Please peruse my posts at your leisure. I am sure there will be no source of debate if you actually take the time.

3. Fine, the plane is moving at 100 mph. What exactly is the riddle? You already said the plane was moving. That's an assumption you made. The plane moves--> the plane can fly if it reaches whatever speed it needs to take-off.

Done? I know I am.

That is not the version that I have seen or read. The version I have read clearly states that the belt matches the speed of the plane, in which case, everything I've stated is correct.

Now, to your version, where the belt matches the speed of the wheels. If the question is phrased that way, then it is unanswerable because it is known as a dichotomy paradox or zeno (xeno) paradox. The dichotomy paradox states that if I want to get somewhere I need to get halfway there first. And from that point I need to get halfway to my destination. A from that point I need to get halfway there. And so on and so forth. So will I ever reach my destination if I keep only getting halfway first?

The point is, the answers go to infinity since you can always split the distance by one half. And thus becomes a paradox, because once you introduce infinity to the equation, it becomes a theoretical concept. You never get to finish the answer. It goes to infinity.

So in regards to the plane/treadmill, the same paradox applies. The wheel always "attempts" to go 1 mph faster than the treadmill and the treadmill catches up in speed. But then the wheel tries to go 1 mph faster, and again the treadmill catches up. This goes on to infinity. Infinity isn't a number, it's a concept. Thus there is no answer because the analysis keeps going on forever. It is "unfinished" to say the least.

So in response to your statements. If the question is was phrased as you put it, there is still not two outcomes as you stated. There still is only one outcome. We just don't know what it is because the answer will never be finished.

But again, I do not believe the original question was a theoretical, cerebral and philosophical as this. Again, the version I have read, and many others, was the belt matching the speed of the plane, not the wheels. And as you can see has it's own set of debates. Yet it has a correct answer and a pretty technical explanation behind it. It seems to be a much more satisfying brain teaser.

The question in the form you pose is purely an exercise in theory and philosophy. It's another form of "what's the sound of one hand clapping" type question, where there is no answer. It's not that the answer or interpretation is debatable, it's that there is no answer. While I can't say for sure, I don't think someone would pose such a question with technical details, if all they were looking for was some buddist meditation and zen-like enlightenment. Why not then ask, "what is infinity?", why go to the details of describing such a mechanical system? Therefore, it is my opinion that the version describing the treadmill matching the speed of the wheels, is an incorrect variant of the original question.