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The "airplane on a conveyor belt" thought experiment... just... ouch.

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Baldour Ngarr Interwarp Plexus Controlled Chaos	Posted - 2008.09.09 18:51:00 - [91] Originally by: Ryysa Err... Plane measures airspeed, not speed at the wheels. Seriously, have you guys even finished school? Most schools don't cover aerodynamics. What people learnt at school has almost certainly got nothing to do with this. ________________________________________________ "I tried strip mining, but I lost, and it's cold flying around in space naked."
Ryysa Paisti Paisti Syndicate	Posted - 2008.09.09 18:54:00 - [92] Uh? Don't know about your country, but in my country you learn in school how a wing works. The most amazing thing is, that people can't grasp the concept of relativity. Ground speed and airspeed are two completely different things. EW Guide - KB Tool - My Music
Baldour Ngarr Interwarp Plexus Controlled Chaos	Posted - 2008.09.09 18:58:00 - [93] Originally by: Ryysa Uh? Don't know about your country, but in my country you learn in school how a wing works. And you just naturally assumed that every other country in the world must always do things exactly the way your country does? And you thought the OTHER people were stupid? ________________________________________________ "I tried strip mining, but I lost, and it's cold flying around in space naked."
Ryysa Paisti Paisti Syndicate	Posted - 2008.09.09 19:11:00 - [94] I do honestly think that these days, every decent school (or at least high-school) teaches you how a wing works. EW Guide - KB Tool - My Music
cold lazarus Amarr Imperial Shipment	Posted - 2008.09.09 19:12:00 - [95] Edited by: cold lazarus on 09/09/2008 19:19:19 Originally by: Ryysa Err... Plane measures airspeed, not speed at the wheels. Seriously, have you guys even finished school? And if you have, did you do so much drugs that nothing is left of your brain? A 12 year old can solve this. Right was not really relying on plane speed to lift the plane but just said that at 100 mph all the bits fit for a healthy take off because I am guessing pretty much that if the plane is lets say standing on a runway and there was a gust of wind that hits the plane it may take off but not in the direction you want it to, so thrust and all sorts of things regulate take off. so the plane is fooled into thinking it had hit 100mph when it has not it can not take off because ALL THE OTHER THINGS THAT REGULATE THE TAKE OFF DONT FIT. Just a guess though. Edited to add this the OP does not state what type of plane. we are all talking about jet engines and stuff when it could be a simple old plane with one engine at the front and that would totaly rely on the pilots skill at flying a plane as to when he has (all the right things in place) to take off wether on a stationery or mobile platform.
Ryysa Paisti Paisti Syndicate	Posted - 2008.09.09 19:24:00 - [96] Originally by: cold lazarus Right was not really relying on plane speed to lift the plane but just said that at 100 mph all the bits fit for a healthy take off because I am guessing pretty much that if the plane is lets say standing on a runway and there was a gust of wind that hits the plane it may take off but not in the direction you want it to, so thrust and all sorts of things regulate take off. so the plane is fooled into thinking it had hit 100mph when it has not it can not take off because ALL THE OTHER THINGS THAT REGULATE THE TAKE OFF DONT FIT. Just a guess though. What are you talking about? How is the airspeed of a plane modified by the conveyor? If it needs 100mph airspeed to take off, how does it matter if there is a converyor under it, or a huge sea, or whatever? Yes, it's ground speed relative the conveyer, is double as much... But how does that affect take off at all? Mh, anyway, this is a waste of time. EW Guide - KB Tool - My Music
Reven Cordelle Caldari School of Applied Knowledge	Posted - 2008.09.09 19:24:00 - [97] Originally by: Ryysa Err... Plane measures airspeed, not speed at the wheels. Seriously, have you guys even finished school? And if you have, did you do so much drugs that nothing is left of your brain? A 12 year old can solve this. You'd think so, but a lot of people have massive issues grasping the concept that the plane uses air as a medium of gaining its motion as well as its lift. Its a shame to see so many people falling flat on their face concerning this one.

CCP Greyscale	Posted - 2008.09.09 19:33:00 - [98] The thing is, anyone who thinks it won't take off is demonstrating that they DO understand aerodynamics (I don't see how you can reach that conclusion without grasping the principles of lift), they're just making a faulty assumption about the effect the conveyor belt would have on the plane's absolute velocity. It's very easy to phrase the question in a way that fairly strongly implies zero velocity as an assumption without actually stating it (at which point it would be flat out impossible rather than merely misleading), which is (in my experience!) a source of confusion. I'd like to go further and suggest that it's the people who don't go through the "don't be daft, it can't take off without any airspeed" phase who don't get aerodynamics, but it's possible I'm just trying to cover my own backside there

Bei Bao Caldari Honey Cluster	Posted - 2008.09.09 19:39:00 - [99] I wonder why landing strips are hundreds of meters long and not all neatly 50 meter conveyor belts? Strip for landing and belt for take off. Would save so much space and noise generated there must be something wrong with the simple example stated by the op me thinks :s
Vabjekf	Posted - 2008.09.09 19:54:00 - [100] Its so frustrating because all you people who don't realize that it will take off are making this much more complicated than it has to be. I want you to 'get it' ;_; Lets try it this way. An aircraft moves through the air. Normally it uses lift to keep it from crashing into the ground. When an aircraft is landed, it also moves through the air. Only it is not making enough lift, so it uses its wheels to keep it from crashing into the ground. The only difference between the aircraft flying and it going along on the ground is what is keeping it from crashing. The wheels do nothing but try their best to eliminate friction. There is no difference between a landed aircraft accelerating itself and a flying aircraft accelerating itself. They both push against the AIR to go forward. What keeps them from hitting the ground (lift while flying, or wheels while landed) DOES NOT MATTER! It moves forward in the same fashion either way! An aircraft on a treadmill is the same as an aircraft on a runway. If you had a runway that was a huge treadmill and a regular runway, and two aircraft side by side, one on each. They would both go down the runway at about the same speed and take off at about the same time. The ONLY difference is that the wheels on the plane that was on the treadmill would have to spin a lot faster, because they are not only countering the friction that the airplane is making moving forward, but ALSO countering the friction that the treadmill is making moving backwards. Since there is a tiny bit of friction still from the wheels it is plausible to say the airplane on the treadmill may be a tiny bit slower at moving forward, but the wheel friction would be small enough to not really make much of a difference. What you guys need to understand is that the airplane IGNORES THE GROUND AT ALL TIMES ANYWAY! Saying that the ground is moving backwards and thus the airplane can not go forward to generate lift is the same as saying since regular ground stays in place the airplane can also not go forward to generate lift! You see, you are all over thinking it. The obvious and simple solution is that the way an aircraft propels itself, and the way its wheels work, the ground does not matter at all! You do not have to even think about the treadmill, its useless! It may as well not even be there as far as the airplane is concerned. Only its wheels may complain, as they will have to spin faster than usual to compensate.
cold lazarus Amarr Imperial Shipment	Posted - 2008.09.09 20:22:00 - [101] Originally by: cold lazarus I have no doubt the plane will take off eventually this with a simple plane but while not being brain box about this stuff I am fairly certain that on a lets say 747 there are quite a few checks that have to be ticked by the computer on the plane if they are not ticked the plane WONT take off, because the plane wheels are going in excess of what they should be get it? ITS NOT about pure physics here or wind speeds and what ever its a question of our beloved health and safety rules and regulations. The question is not specific enough to justify a simple yes it will take off or no it will not. let me run this by you I know that the 747 safety procedure rule 831.4567 states that if physics mumbo-jumbo is all ok but ground speed is xxx% under/over a certain limit plane will not take off. I bet you $2b that a plane on a moving platform as OP has posted said plane WILL NOT take off because I know land speed will be in excess of its limit and safety protocol demands plane does not lift off. (even though it could) would I win the bet ? answer is yes its a technicality that the plane wont lift off but its the technicalities that count.
Akita T Caldari Navy Volunteer Task Force	Posted - 2008.09.09 20:37:00 - [102] Originally by: Bei Bao I wonder why landing strips are hundreds of meters long and not all neatly 50 meter conveyor belts? Strip for landing and belt for take off. Would save so much space and noise generated there must be something wrong with the simple example stated by the op me thinks :s The plane needs the same length of runway to take off, wether it's tarmac or conveyor belt... actually, no, due to small degrees of additional friction, you would need a slightly LONGER conveyor than you need tarmac to take-off if the conveyor moves like described in the OP. Obviously, if the situation was reversed (i.e. conveyor and plane moving in the SAME direction, not opposite), you'd need a (very slightly) smaller conveyor than runway. Still, the differences are negligible (think below 1%, tops). What would make sense is if the conveyor could accelerate the conveyor plus aircraft faster than the airplane could do by itself, but you'd need a system that can lock the wheels to the conveyor until it's time to lift-off, then suddendly release them. At the landing however, it's exactly the opposite... with a conveyor belt moving "backwards", you actually DO need less total ground length to stop, since you apply brakes on the wheels that touch the conveyor. [sarcasm] You know, it's almost as if somebody could have thought of that already... ...oh, wait, they DID. It's called an aircraft carrier. [/sarcasm] The take-off is via hydraulic catapult which locks on to the wheel train, accelerating the plane faster as it can do by itself, and releasing it at the end of the runway, thus reducing the needed take-off length. Not only that, but launches and landings are made (whenever possible) while moving "into" the wind to even further increase the air-speed while minimizing plane-to-carrier speed. _ SHOPS \|\| Mission rewards revamp \|\| better nanofix
Lance Fighter Amarr	Posted - 2008.09.09 22:23:00 - [103] Yep :) dont forget the catch cable thingies in the back to land on. Originally by: Dheorl Originally by: Akita T yawn I never knew it was possible to stretch your ego THAT much in 1 post
Pria Pus	Posted - 2008.09.09 22:52:00 - [104] Forgive me for being a total jerk in physics... but for these ever again mentioned Mythbustersthing - i saw it. And, guess what, the plane actually moves forward before lifting off. The conveyor was at no point fast enough to negate movement totally. Even if i **** somebody off now - but when referring to an experiment, please do so to a proper executed one. I thought the joke of an airplane lifting from the ground is its speed with wich it is moving through the surrounding air. So if the belt underneath the plane is negating all movement from the plane - how can it lift off then? Only by the engines? Then every single plane would be a jump jet. As long as the surrounding airspeed is not exeeding its liftoff speed nothing is happening, or? A plane inflight getting too slow to even glide will drop like the said stone into the ground. So if there is no movement at all from the plane it can't lift off. so where is my mistake? The plane stands still in relativity to the surrounding air as long as the belt works properly. Engines loud, wheels spinning like crazy - only the poor plane is sitting point. So how to lift off, then? Somebody try to explain it in simple words, plieeesss? Even with the carrier-example something is borked. Because here also the plane is speeding through the surrounding air up until speed reaches takeoff limits and then it starts to fly. Or is the main mistake i make that i still have a jetengine propelled craft in my mind and i need a propeller to maintain 'wind'?
Akita T Caldari Navy Volunteer Task Force	Posted - 2008.09.09 23:09:00 - [105] Originally by: Pria Pus So if the belt underneath the plane is negating all movement from the plane - how can it lift off then? That's the problem... you're ASSUMING that the plane SHOULDN'T be able to move forward. Take a look at the picture linked at the end of the OP, re-read the bolded part, look again at the picture if needed... and just try to understand that there's absolutely NO REASON for the plane to be unable to move forward. _ SHOPS \|\| Mission rewards revamp \|\| better nanofix
Sharupak Minmatar Brutor tribe	Posted - 2008.09.10 00:01:00 - [106] Edited by: Sharupak on 10/09/2008 00:03:10 Edited by: Sharupak on 10/09/2008 00:01:29 Here is probably a better visual with something everyone here has more experience with. Get rid of the plane and imagine you are in your car on a treadmill as long and wide as a normal road except the treadmill is slanted at a 45 degree angle your car is pointed in the direction downhill. Now put the ****ing car in neutral at the same time the treadmill starts moving uphill. How many of you still think your car is going to stay in one place? If you still do, please imagine a cliff at the end of the treadmill road so that you car will fly off of it into a canyon and you die! _______________________________________________ RuntimeError: ChainEvent is blocking by design, but you're block trapped. You have'll have to find some alternative means to do Your Thing, dude.
Daelorn Perkone	Posted - 2008.09.10 01:52:00 - [107] The money used to build the LHC would of been put to better use to making a runway sized treadmill. I honestly think it wouldn't take off if the treadmill was constantly matching the speed of the airplane. Planes have a maximum speed. Some of you say that the air around the plane is standing still but the ENGINE still sucks in air so the engines can reach its top speed, but it still standing still, and its the wings that provide lift. DOES I MAEK CENTS?!
Sharupak Minmatar Brutor tribe	Posted - 2008.09.10 02:22:00 - [108] Look, its not that hard! Teh speed is teh samez!!!! _______________________________________________ RuntimeError: ChainEvent is blocking by design, but you're block trapped. You have'll have to find some alternative means to do Your Thing, dude.
Woodwraith Digital assassins G00DFELLAS	Posted - 2008.09.10 02:55:00 - [109] Originally by: Pria Pus Or is the main mistake i make that i still have a jetengine propelled craft in my mind and i need a propeller to maintain 'wind'? It doesnt matter, its newtonian physics, you can just as well picture the plane laying on the ground with a perfectly frictionless grease on its belly, or a maglev levitation, or anything else. were assuming for the sake of it that the wheel bearings are frictionless, and the wheels have zero mass. In reality, the wheels would overheat and come off the hubs and everybody dies, but in reality no ones got a treadmill to do this anyway, so whatev. the thrust goes backwards, the plane goes forwards, and takes off at some arbitrary airspeed, dont worry about what the wheels are doing, thats the bit thats in there to throw people off.
NanDe YaNen The Funkalistic	Posted - 2008.09.10 03:54:00 - [110] I'm compelled to answer this one. It takes off. The reason is that the force exerted by the conveyor belt is only due to friction. The plane will basically remain at rest as long as the breaks are off. The conveyor belt moves. The wheels turn as if the plane is moving forward. The plane effectively goes nowhere. Add thrust. The force balance is now such that the airplane takeoff appropriate thrust is only having to overcome a very minimal amount of force exerted by the conveyor belt via overcoming friction and inertia of the wheels. Takeoff thrust = Big Frictional force + force required to counteract reaction force at the pivot of the wheels as they are accelerated about the pin = Small From a ground perspective, the plane has a net forward force and will accelerate forward until it has achieved takeoff velocity. Only wrench thrown in this is if the conveyor belt moves fast enough to cause the tires to heat up and blow out and the friction of the naked landing gears is enough to accelerate the plane in the other direction. Similarly, the plane might go out of control if the wheels blow up one by one (likely). There's also the possibility it's fitted with a cloaking device and the operator never knows to turn the conveyor belt on, but this also means the plane only has one burst of MWD available to leave the bubble without getting decloaked. --------------------------------------- Originally by: Red Raider A happy gamer isnt on the forums, they are playing the game unless they have an idea that they honestly think is helping out.
micki	Posted - 2008.09.10 05:36:00 - [111] Looking at the 2 extremes 1 stick wheels on a firework, light it, wave goodbye 2 old boy in his pedal powered glider, peddling furiously, doing nothing apart from sweating. So no right answer
YouGotRipped Ewigkeit	Posted - 2008.09.10 05:52:00 - [112] Of course it will take off. WTF is this? Oh, it's an Akita T thread. lol
NanDe YaNen The Funkalistic	Posted - 2008.09.10 06:11:00 - [113] Originally by: CCP Greyscale 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. You wrote destiny, didn't you! Everything forgiven as long as you have the "oh, duh" moment the next time around :-) --------------------------------------- Originally by: Red Raider A happy gamer isnt on the forums, they are playing the game unless they have an idea that they honestly think is helping out.
Rawrior Gallente Neo Spartans	Posted - 2008.09.10 09:44:00 - [114] Originally by: Death4free the answer is yes because its a harrier jump jet... this should have killed the thread, why are you still talking??? Owing to lack of Eve-related content, signature removed. If you would like to discuss this, please mail [email protected] - Mitnal
ivar R'dhak Sebiestor tribe	Posted - 2008.09.10 11:22:00 - [115] Interesting. I actually first thought NO in a knee jerk reaction. Then came the mental god-youa-dump-b!tchslap. It¦s very telling how our natural everyday locomotion (legs pushing at ground = movement in opposite direction) dictates our perception of ALL movement. I find it very disturbing that even supposedly "intelligent" people fall for the No-Argument and vehemently defend it. No wonder that the pinnacle of scientific accomplishment nowadays is akin to people throwing rocks at each other to find out what happens next (LHC ). _ Mal-`Appears we got here just in a nick of time. What does that make us?¦ Zoe-¦Big damn heroes sir.¦ Mal-¦Aint we just.¦
Evanade Rionnag Alba Triumvirate.	Posted - 2008.09.10 11:24:00 - [116] it's called 'airspeed' for a reason --------------------------- sok alt - main got banzored
MotherMoon Huang Yinglong	Posted - 2008.09.10 11:26:00 - [117] it's been done. watch mythbuster the plane stays still and it takes off. why? Because the wheels are not powered they don't help the plane move forward or backwards or any such way, you turn on the engine and the wheels stay it place for a moment and then the plane moves forward over the belt no matter how fast the belt is moving because the propellers or jets or whatever push the plane forward and thus up ignore the belt.
MotherMoon Huang Yinglong	Posted - 2008.09.10 11:30:00 - [118] Edited by: MotherMoon on 10/09/2008 11:36:28
Myrhial Arkenath Ghost Festival	Posted - 2008.09.10 11:31:00 - [119] Mothermoon is correct. They even redid the experiment I believe because viewers weren't happy with the original one. Diary of a pod pilot
P'uck	Posted - 2008.09.10 13:09:00 - [120] This thread, it makes me wanna slam my head against the wall, more than any of my girlfriends ever did... and the last one even had a black belt in PMS'ing. But I guess I'll just have to accept it. The "Monty Hall paradoxon" is easy to solve, too, just like this one. But I'm better with physics than with probability calculations (or however you call it in english). But AT LEAST I know that, and therefor refrain from shouting around my (most likely) wrong answers in the monty hall thread. Seriously, this feels like a science thread for creationists.

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