If that’s what you think, then you don’t know what treis is talking about.
But there is no point in talking further till you confirm that we are talking about a version of the question and background assumptions per 1/ and 2/ of my post above.
If you do confirm that, then we can talk more.
Christi7df, will you at least acknowledge that the force from friction between the wheel and the treadmill is imparted onto the body of the plane through the axel?
I will repeat one more time in case you missed it.
If you want to twist it into the ridiculous, then you can torture the puzzle to say that the belt can move at ridiculous speeds as Cecil stated. But if you can give the belt ridiculous magic capability to hold the plane back, then why can’t I give the airplane ridiculous magic capability to overcome the force of the magic conveyer?
If you can do that with the belt, then why can’t I do the same with the airplane? Then you have a paradox as Cecil stated.
I prefer to stick to real world possibilities.
Under your premise perhaps the plane would fly. However, the original premise of the question was that the treadmill matches speed with the plane’s wheels - there is no forward movement to generate wing lift.
I’ve said nothing about the speed of the treadmill merely its acceleration.
Treis is basically answering the question “how fast do I need to accelerate a treadmill in order to hold an aircraft at full power motionless?” If you don’t wish to discuss that question then I fail to see why you are engaging Treis at all.
The puzzle is already ridiculous just by having a treadmill the size of a runway. I think it is reasonable, if you are to exagerate the abilities of something, to exagerate the abilities of the treadmill as it is already outside the realms of practicality.
Then you should avoid answering the question entirely as there is nothing real world about it, no matter how you interpret it.
The question as answered by Cecil is so simple that it doesn’t even deserve to be asked (let alone answered.) Allowing the treadmill very high acceleration makes for a slightly more interesting discussion.
Either way. The speed would eventually have to reach the ridiculous in order to hold the airplane still.
But then, as long as you are playing make believe, you just give the airplane the as much capability is needed to overcome the ridiculous belt.
If you read Cecil’s answer carefully you’ll note that he uses the same premise that I do. The aircraft moves forwards at 100 mph, the conveyor moves backwards at 100 mph, relative speed between aircraft and conveyor is 200 mph, relative speed between aircraft and the air/ground is 100 mph, aircraft flies.
If you want the conveyor to stop the aircraft from moving at all then of course the aircraft won’t fly, however you’ll need to justify how the conveyor actually manages to keep the aircraft from moving, which is what Treis is doing.
Dude, I am playing make believe just as much as you are. The engine required to turn a 11,000 foot treadmill at 500 mph is ridiculous. The 22,000+ foot continous piece of rubber for a treadmill is ridiculous. The support required to hod up a 400 ton object on a treadmill is ridiculous. The whole damn problem is ridiculous. I have no idea why you are putting your fingers in your ears and going “LALALLALLA” over one ridiculous treadmill and not the other. I also have no idea why I am even bothering with this anymore.
That is fine as long as you are just playing make believe.
But the problem as I see it is when you are playing make believe, you can make believe anything.
Are we children just playing make believe?
We can just discuss all kind of impossible things then. I thought this board was supposed to be science related.
I guess that this is not the place for me.
It is all “make believe”. The whole concept is ridiculous. However, everyone else is playing “controlled make believe”.
I don’t see why you are happy to have a treadmill the size of a runway (a ridiculous proposition) but as soon as someone asks what may happen if we give the treadmill some extreme acceleration, you throw your hands up and say “oh it’s all make believe now, you’ve taken away my real world 2 km long 60 m wide treadmill and replaced it with one that can do other stuff! Well, we may as well have the plane piloted by blue elephants!”
Not necessarily. You don’t have to use a large airplane. The puzzle does not require that. Some airplanes have takeoff speeds much less than 100 mph. I think it may be possible to make a belt that could get up to that speed.
I think that it is possible to actually do this experiment if someone wanted to go to the trouble with a smaller propeller airplane.
And I would prefer to stick to the puzzle as written, not saying that the belt is actually trying to hold the airplane still. Only as stated in the puzzle that it matches the forward motion of the airplane. To me that means air speed.
You would not even have to have a long belt as I stated before. Keep the belt low to the ground. All you have to show is that the airplane would just roll off the end of the belt and continue on to takeoff.
“Now’s where the sniveling solipsists/philosophic idealist infants start whining about ‘How can you KNOW objective reality? Isn’t everything appearance?’ At which point, I grab a beefy, hardbound copy of Kant’s Critique of Pure Reason, and whomp 'em upside the head but good !” — Joseph Moore.
Thought that was a good quote.
Well friend, this is as a good time as any to discover that not everyone reads the problem the same way as you nor is your interpetation somehow superior in this case.
I’m going to have to chalk this one up to the poor wording of the original question, by my reading - “conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same” - means that the plane will have no forward motion and hence no wing lift. Granted it is 1AM here and I’ve been up for about 32 hours, am I missing something obvious? The plane remains stationary - no forward motion, no wing lift, no flight.
Discussion of impossible things is fine as long as you define what you are discussing. Often impossible things are brought in to a thought experiment in order to shed light on the subject that we are investigating. That’s what a thought experiment is relly, it’s why it’s not a real world experiment, because it can’t be done in the real world. But it is still ok to play “what if.”
Not necessarily true. There are a lot of different people and discussions here. Plenty of people stay well clear of debates, prefering to talk about movies or their weekend or just stick to factual questions. There is a place here for most.
The puzzle, as written, is not worth building a huge conveyor for. The answer is simple and obvious, the aircraft flies.
Really, you either assume the aircraft can move in which case it obviously flies. Or you assume it doesn’t, in which case it obviously doesn’t fly. The only time it gets anything like interesting is if you try and figure out just what kind of conveyor belt could possibly stop the aircraft from moving.
We played “make believe” all the time in high school physics. Ever heard of massless pulleys? Frictionless bearings? Fully rigid bodies? None of those exist in the real world; instead, they are concepts we used to simplify problems when the effects of friction, mass, and deflections were small enough to ignore. Believe me, it’s much easier for 16-year-old to learn about free acceleration when you don’t have to solve differential equations to account for the effects of the atmosphere.
Even in graduate-level mechanical engineering courses, we make simplifying assumptions all the time – sacrificing a few percentage points of accuracy isn’t such a loss if you’re saving hours or days of computing time. Especially if your simulation is still has higher accuracy than your measurements. 
As 1920s Style “Death Ray” says, it’s make believe within a strictly defined framework of physics. The military does this all the time with their wargames, and they’re not playing Calvinball. Airline pilots can be exposed to anything and everything that will go wrong by using the safety of a simulator. And here, we’re developing thought experiments based on undergrad-level physics. Why? It’s a workout for our minds, an exercise of creativity in an otherwise rigid discipline. That is what inspires discovery, and that it why the Straight Dope exists.
Yes it is poorly worded. There are two distinct interpretations. Yours is not wrong at all, but it is not the same as Cecil’s interpretation, therefore you can’t say that he is “wrong”, only that the question he is answering is different from the one you are answering (despite them having the same words :))
But if the plane has no forward motion, then why is the belt moving at all?
Thanks for the clarification “Ray” I joined the discussion late in the game. Your right I should have been clearer.