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Akita T
Caldari Navy Volunteer Task Force
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Posted - 2008.09.09 12:01:00 -
[1]
Seriously, I never heard of it before today (although it's supposedly quite a heated "internet argument"), and it was just an obscure reference in the latest XKCD "footnote" (but the discussion thread in the forums was quite... ahem... lively).
Still, I almost couldn't believe it IS an argument at all in the first place.
I mean, I knew there's plenty of dense people who never paid any attention in basic physics, but to hear that people who CLAIM to be pilots or engineers are arguing about the incorrect answer is just... ungh.
If you are like me and never heard of the thought experiment until today, I'll spare you the google search time and just post it here... I'm curious what the rationale any of you can provide for the WRONG answer.
" An airplane is standing on a (very/sufficiently) long, powerful and fast conveyor belt.
The airplane pilot attempts to take off moving forward.
The controller of the conveyor belt is making the conveyor belt move in the opposite direction with the same speed.
Can the plane take off, yes or no ? "
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Taua Roqa
Minmatar
Groping Hand Social Club
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Posted - 2008.09.09 12:05:00 -
[2]
it will have thrust but no lift, infact the engines would probably stall or something due to little air intake...but then again i am not a pilot :/
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Le Skunk
Low Sec Liberators
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Posted - 2008.09.09 12:06:00 -
[3]
NO
My justification? Well when im down the gym pushing weights and all the birds checking me out and shit. I sometimes have a go on the running machine (i push one of the wimps on it out of the way first, the birds all luagh and giggle behind their hands).
And i dont take off do i.
SKUNK
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Moneeh
Minmatar
Pator Tech School
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Posted - 2008.09.09 12:07:00 -
[4]
I think it's pretty obvious that it will not take off.
Using my advanced physics skills (  ) I'd say that the plane's speed will be annihilated by the opposite direction of the conveyor belt. So from a 3rd person perspective it would appear that the plane stands still.
..i think :S
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Death4free
Caldari
Ninjas N Pirates
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Posted - 2008.09.09 12:10:00 -
[5]
the answer is yes because its a harrier jump jet...
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Nalta Nightbringer
Amarr
Angels of the Abyss
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Posted - 2008.09.09 12:12:00 -
[6]
Mythbusters had a special on this kind of thing. Turns out, the plane took off. Something about how it still moved forward because the thrust was on a different level or something, it's been awhile.
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Kyrall
A Few Killers
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Posted - 2008.09.09 12:16:00 -
[7]
I was working in a defence research place a couple of years back and this came up, so the type of people working there lead to some interesting discussions. Most of them were from a computer science background, and as the only one from a mathematics background I was the one to say that it absolutely depends on very careful interpretation of the exact meaning of the question.
The question is usually pretty short, so there are many different things not covered by it, so you can examine loads of different situations depending on the many variables. For example: there are a few ways you can handle things like friction, and whether the conveyor belt is always at exactly the same speed as the aircraft (or its wheels) or if it is just trying to keep up (so there is a slight delay).
One situation leads has the wheels spun up to infinite speed as soon as the aircraft starts to move. Then of course you have to decide whether the wheels are infinitely strong or if they melt/explode...
_____ Originally by: Pwett
You sir, underestimate the things I have and will pee on.
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Lord Zoran
House of Tempers
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Posted - 2008.09.09 12:24:00 -
[8]
Originally by: Death4free
the answer is yes because its a harrier jump jet...
rofl.....
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Akita T
Caldari Navy Volunteer Task Force
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Posted - 2008.09.09 12:25:00 -
[9]
Originally by: Moneeh
Using my advanced physics skills () I'd say that the plane's speed will be annihilated by the opposite direction of the conveyor belt. So from a 3rd person perspective it would appear that the plane stands still.
Ok, let me ask you a DIFFERENT question then, just for you... to understand just where you're wrong...
If you and me (assumed to be identical in physical stats) are sitting on an icy lake and there's two wooden planks on top of eachother, and I want to move the upper plank in my direction, while you attempt to stop me from doing that by pulling the bottom plank in the opposite direction... can you stop me ?
Or, better still, what exactly do you think it will happen ?
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Taua Roqa
Minmatar
Groping Hand Social Club
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Posted - 2008.09.09 12:28:00 -
[10]
so what's the right answer? i am saying it could take off - as the wheels would act like a kind of gear negating the movement of the conveyor belt.
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KaiTech
Polaris Project
Curatores Veritatis Alliance
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Posted - 2008.09.09 12:29:00 -
[11]
The plane would only take of if the airspeed around it's wings would be high enough, it's got nothing to do with the groundspeed.
for instance why do U think airplanes lift off faster if they take off in opposite direction of the wind direction (face the wind)
The only thing that is relevat to flying is the speed of the air, another example, ...:
ever observed an Eagle float above U and it looks as it was standing on 1 place in the air ? ... well that's only possible if it can face the wind and if the wind is blowing fast enough for it to be able to support the weight of the Eagle. Would the wind stop blowing a t the minimal speed it would fall like a rock or it would have to flap it's wings.
So the answer in the case that if U'r conveyor belt isn't producing a sufficient airstream to make the plane lift off it's gonna stay on the ground.
So basically the short answer is : no!
cya in game soon
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Reven Cordelle
Caldari
School of Applied Knowledge
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Posted - 2008.09.09 12:29:00 -
[12]
Since a plane is not powered through its wheels, the plane will still take off.
Consider the fact a plane will move itself by "grabbing" the air in front of it. the air is there, it is not moving with the conveyor.
The plane will therefore merely take off as per usual, its landing gear will be moving in the direction of the conveyor, but since the landing gear has no drive and is merely freewheeling, it'll provide no problem for the plane to travel along the conveyor regardless of how fast the conveyor is moving. Since the wheels can move as fast as they can, the plane is free to take off at its own will.
Pretty simple, barely requires debate.
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cytomatrix
Caldari
Carebear Killers Inc.
Anarchy.
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Posted - 2008.09.09 12:31:00 -
[13]
I think it will. Because the plane is not propelled by its wheels, but by its propeller/jet engine. Plane's energy is working on Air. Wheels are they to avoid friction between plane and the ground. I could be wrong. I am not very good at physics.
______________________________________________________________
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Kaeten
Hybrid Syndicate
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Posted - 2008.09.09 12:33:00 -
[14]
it WON'T take off due to the fact that it's the wings that lift the plane, and as the wings are basiccly stadning still how could they lift the plane, it needs air passing around the wings for it to generate lift.
What stupid idiots thought of that.
________________________
I'M POOR
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Etumretniw
Minmatar
Sebiestor tribe
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Posted - 2008.09.09 12:35:00 -
[15]
Originally by: Reven Cordelle
Since a plane is not powered through its wheels, the plane will still take off.
Consider the fact a plane will move itself by "grabbing" the air in front of it. the air is there, it is not moving with the conveyor.
The plane will therefore merely take off as per usual, its landing gear will be moving in the direction of the conveyor, but since the landing gear has no drive and is merely freewheeling, it'll provide no problem for the plane to travel along the conveyor regardless of how fast the conveyor is moving. Since the wheels can move as fast as they can, the plane is free to take off at its own will.
Pretty simple, barely requires debate.
This.
The only difference between this scenario and a normal take off, is that the wheels will spin twice as fast.
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Akita T
Caldari Navy Volunteer Task Force
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Posted - 2008.09.09 12:38:00 -
[16]
Originally by: Kyrall
it absolutely depends on very careful interpretation of the exact meaning of the question.
The question is usually pretty short, so there are many different things not covered by it, so you can examine loads of different situations depending on the many variables. For example: there are a few ways you can handle things like friction, and whether the conveyor belt is always at exactly the same speed as the aircraft (or its wheels) or if it is just trying to keep up (so there is a slight delay).
Well, while it's a short version, it's not really up for interpretation.
The only sound logical conclusion to the exact wording I used in the OP is that the speed of the conveyor is the same as the speed of the plane (relative to the ground/air), but in the oppposite direction.
So the airplane WILL take off, but its wheels will be spinning at double the usual rate at take-off.
The only other (ill-)conceivable (mis-)interpretation option would be the one you just presented as absurd already, in which the conveyor belt attempts to match the wheel contact speed instead of that of the airplane ground/air speed, up to the point where friction in the wheels (assuming they could handle it without exploding) would create enough drag to nullify the propeller thrust, keeping the airplane stationary.
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Ryysa
Paisti
Paisti Syndicate
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Posted - 2008.09.09 12:39:00 -
[17]
Originally by: Kaeten
it WON'T take off due to the fact that it's the wings that lift the plane, and as the wings are basiccly stadning still how could they lift the plane, it needs air passing around the wings for it to generate lift.
What stupid idiots thought of that.
Actually, you are the idiot.
It's a plane, not a car. Who the hell cares how fast or slow it's wheels spin...
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clone 1
Laughing Leprechauns Corporation
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Posted - 2008.09.09 12:47:00 -
[18]
YES
Of course it would, silly internet people
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The Angels Have the Phone Box |
Reven Cordelle
Caldari
School of Applied Knowledge
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Posted - 2008.09.09 12:48:00 -
[19]
Originally by: Kaeten
it WON'T take off due to the fact that it's the wings that lift the plane, and as the wings are basiccly stadning still how could they lift the plane, it needs air passing around the wings for it to generate lift.
What stupid idiots thought of that.
So the planes wings are now connected to the ground? The wings are a device of lift, not propulsion.
Plane landing gear is freewheeling, the prop/turbine moves the plane. If the AIRSPEED was moving at the same rate as required for the plane to take off, THEN the plane would essentially FLY on the spot providing it could get up to the local airspeed before crashing.
Ground speed is not even a factor for a plane taking off. The wheels can spin as fast as the conveyor, essentially negating any effect of the conveyor in the first place.
Unless you factor in material thresholds, friction and operational boundaries of the wheels, bearings and axles of the planes landing gear. In that instance the conveyor would have to be moving incredibly fast and merely poses the debate of variables.
Since that view is moot to the original debate;
The plane will take off.
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Voltain
BEER Inc.
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Posted - 2008.09.09 13:18:00 -
[20]
Air needs to pass over a wing at the correct velocity and angle to create lift.
If you run on a treadmill in a gym itĘs not bloody windy is it.
A plane running flat out on a treadmill is not moving through the air, its position is static, there is no airflow, engines will not magically create this, and if they did we wouldn't need runways.
What this theory needs is a MASSIVE FAN, the airflow over the wings will create lift, the thrust from the engines will propel the plane into said MASSIVE FAN where it will be chopped to bits and a fireball will erupt when the blades smash into the fuel tanks.
DesuSig |
clone 1
Laughing Leprechauns Corporation
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Posted - 2008.09.09 13:21:00 -
[21]
Originally by: Voltain
Air needs to pass over a wing at the correct velocity and angle to create lift.
If you run on a treadmill in a gym itĘs not bloody windy is it.
A plane running flat out on a treadmill is not moving through the air, its position is static, there is no airflow, engines will not magically create this, and if they did we wouldn't need runways.
What this theory needs is a MASSIVE FAN, the airflow over the wings will create lift, the thrust from the engines will propel the plane into said MASSIVE FAN where it will be chopped to bits and a fireball will erupt when the blades smash into the fuel tanks.
Stop it you're killing me 
--------------------------------------------------
The Angels Have the Phone Box |
Reven Cordelle
Caldari
School of Applied Knowledge
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Posted - 2008.09.09 13:24:00 -
[22]
Originally by: Voltain
Air needs to pass over a wing at the correct velocity and angle to create lift.
If you run on a treadmill in a gym itĘs not bloody windy is it.
A plane running flat out on a treadmill is not moving through the air, its position is static, there is no airflow, engines will not magically create this, and if they did we wouldn't need runways.
What this theory needs is a MASSIVE FAN, the airflow over the wings will create lift, the thrust from the engines will propel the plane into said MASSIVE FAN where it will be chopped to bits and a fireball will erupt when the blades smash into the fuel tanks.
Haha,
Thats hilarious.. massive fan...
Lol.
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Kirala Hcsirf
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Posted - 2008.09.09 13:25:00 -
[23]
Exactly.
http://en.wikipedia.org/wiki/Bernoulli's_Principle
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Voltain
BEER Inc.
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Posted - 2008.09.09 13:27:00 -
[24]
You read it hear first.
MASSIVE FANS will be coming to BAA Airports near you soon.
DesuSig |
Vabjekf
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Posted - 2008.09.09 13:33:00 -
[25]
The answer to the question is that it will take off. In reality however it would depend on how good the wheels were. Wheels are not frictionless.
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Int3r
Minmatar
Athena Enterprises
Caduceus Alliance
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Posted - 2008.09.09 13:34:00 -
[26]
Originally by: KaiTech
The plane would only take of if the airspeed around it's wings would be high enough, it's got nothing to do with the groundspeed.
for instance why do U think airplanes lift off faster if they take off in opposite direction of the wind direction (face the wind)
The only thing that is relevat to flying is the speed of the air, another example, ...:
ever observed an Eagle float above U and it looks as it was standing on 1 place in the air ? ... well that's only possible if it can face the wind and if the wind is blowing fast enough for it to be able to support the weight of the Eagle. Would the wind stop blowing a t the minimal speed it would fall like a rock or it would have to flap it's wings.
So the answer in the case that if U'r conveyor belt isn't producing a sufficient airstream to make the plane lift off it's gonna stay on the ground.
So basically the short answer is : no!
cya in game soon
This.
I can't believe that there's actually an argument about it
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Akita T
Caldari Navy Volunteer Task Force
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Posted - 2008.09.09 13:36:00 -
[27]
Edited by: Akita T on 09/09/2008 13:36:43
Originally by: Voltain
If you run on a treadmill in a gym it’s not bloody windy is it.
That's because you're running on the treadmill USING YOUR LEGS ONLY to move with relation to the treadmill.
Try to put on rollerskates, THEN try to move forward.
After that, strap some high-pressure fire extinguishers to your back and just sit still while you fire them.
Quote:
A plane running flat out on a treadmill is not moving through the air, its position is static
Says who ?
Did you actually read the OP ?
The conveyor is MATCHING the airplane's speed in the opposite direction, therefore the airplane IS moving (say left) while the conveyor is moving (right) at the same speed.
The velocity DIFFERENCE between the airplane and the conveyor is exactly double of that between the ground/air and the conveyor surface or the airplane and the air, therefore the wheels will be spinning twice as fast.
It's no different than, say, the airplane trying to lift-off with wind BLOWING FROM THE BACK at the same speed it would need to take off... the plane WILL take off, but the actual speed at take-off (compared to the ground) is double.
The reverse case (wind blowing from the front) would be the plane taking off while standing still (horizontally, with regards to the ground, that is).
Hell, imagine wind blowing at higher speed than needed for take-off... the plane would take off moving BACKWARDS.
The WHEELS of an airplane don't provide propulsion, the propellers do.
The PROPELLERS provide propulsion against the air, not the ground.
The conveyor does NOT cause the air to move, it can only cause the wheels to spin faster.
Wheel friction drag is negligible compared to propeller thrust, unless you move the conveyor at insane speeds risking to actually break the wheels (but you were limited to the speed of the plane anyway, so it's not an issue).
Therefore, the plane DOES move forward.
And because it moves forward, it WILL eventually take off.
P.S.
Seriously, I had to see this to believe it... some people REALLY ARE that dense, are they not ?
And apparently, they also post before reading the bolded parts of the OP carefully, let alone parse the entire thread.
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Int3r
Minmatar
Athena Enterprises
Caduceus Alliance
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Posted - 2008.09.09 13:41:00 -
[28]
The plane will not take off at all, because the propellors have to provide all the airflow for the entire wings.
In normal circumstances, the propellors provide the speed, and the air (standing still) provides lift because the plane moves through it.
Now there's no airflow from the air, just the air that the propellors move backward, that won't be enough, not even at twice the speed.
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Akita T
Caldari Navy Volunteer Task Force
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Posted - 2008.09.09 13:42:00 -
[29]
Edited by: Akita T on 09/09/2008 13:44:26
Propellers provide THRUST.
Wings provide LIFT.
Wheels provide SUPPORT and low friction.
Conveyor only affect the WHEELS. NOT the propeller.
The airplane IS moving forward.
Wheels are just spinning twice as fast as normal.
The airplane WILL take off.
Also, reread the post right before yours, please, if you STILL don't get it.
If you still disagree... *sigh*
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SHOPS || Mission rewards revamp || better nanofix
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CCP Greyscale
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Posted - 2008.09.09 13:42:00 -
[30]
My initial reaction was "no, if it's stationary there's obviously no way it'll get lift". Then I did some poking around the interwebs because I figured that if it was that simple there's no way the argument would get off the ground (har har), which in turn led to the "oh, duh, i r dum" moment. Plane speed, even on the ground, is determined by the engine thrust, and the conveyor belt won't make the blindest bit of difference to that. The implicit assumption that the conveyor belt is keeping the plane stationary is complete bunk when you actually think about it - there's no mechanism by which the fact that the ground is moving backwards can have any effect on the acceleration generated by the engines, ignoring tiny amounts of bearing friction.
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