Will it Fly?

[aurik]

It's not that complicated.

*The jet engines create a forward force on the object.
* Since we are assuming a perfect wheel, any tangential force applied to the wheel (ie, that from a treadmill) creates no force on the object.
* Therefore the net force on the object is forward.
* Therefore the object attains a forward velocity.
* Assuming the air is stationary, this creates a velocity of the wing through the air
* This creates an upward force due to the shape of the wing

If you have a perfect wheel, no amount of speed is going to stop the plane from moving forward.

If you have an imperfect wheel, then it is no different than offsetting the jet force with a tether to a nearby tree: the treadmill creates a perfectly opposing force to the thrust of the engine, therefore the plane has no net force, does not move, and does not get an upward force from the velocity of the wing through the are.

[Skyylya]

I was arguing on the base that this was theoretically realistic but if there are no parameters on the speed of the treadmill-ground then it is no longer theoretically realistic and there is no finite answer to the question as anything could be possible, or impossible.

I disagree. The parameters were very clearly defined in the original problem. It said specifically that at any point in time t, if the velocity of the plane is v(t), then the velocity of the treadmill is -v(t). As such, the parameters on the speed of the treadmill are as follows:

K > v(t) >= 0

where K = max| { V : an actual plane has achieved lift at velocity V at some time between 1900 and now } |

Are you saying that theoretically unrealistic problems do not have answers? That's odd, because mathematics does not depend on physics, it's the other way around. As long as the mathematics is valid, then so is the answer, regardless of how nonsensical the problem is.

I can talk about a plane with a velocity of 4 + 7i, where i is the square root of -1, and it makes for perfectly solvable problems.

I suck at math, i'm good at understanding concepts. So while we might discuss the same thing I don't understand the language you're speaking. There are a lot of things I can do and understand because I get the concept behind it, but still not know mathematically how it works.

Basically Aurik said what i'm trying to say better than anyway that I said it and more concise. Regardless of what is going on, on the ground the force from the jet propulsion will still push the plane forward. The ground is re-active and not pro-active on the planes movement and technically has no 'force' of it's own that is holding the plane back. So your equation while mathematically correct assumes that the ground has a negative force on the propulsion of the plane.

[Jotaru]

Hm.. Well, even on an imperfect wheel, it will have a resistive force, but not one to match the engines, or a plane would never take off. The situation comes down to (in theory) the wheels having to spin twice as fast and generating 2x as much frictional force, but that's no different than if a plane that normally rotated for liftoff at 150mph just had to stay on the ground till 300. It's not just gonna magically lock up the wheels and stop, pending the landing gear doesn't asplode.

[ozz]

mythbusters ses it takes off
btw sorry for necro but its a worthy addition!

[Skyylya]

god damnit ozz you beat me to it.

but damnit I WAS RIGHT

[ozz]

gonna have to say you weren't...although you said it would fly if the treadmill was an unreasonable length, that's the way the mythbusters tested it so you should be considering it an invalid, pointless test

Jotaru: I'm not taking anything personally, but the fact of the matter is that when you change the size of the treadmill to be anything other than the relative size of the plane it is no longer a 'treadmill' and the concept is no longer valid of if it can fly on a treadmill or not. If you run on a treadmill and set the speed to something that you can moderately run on but still go faster, the size of the treadmill inhibits you from being able to move forward on it, if you took a treadmill and stretched it out 20 feet and set it to the same speed, you could run from one side to the other but what's the point, it's not longer a treadmill because it doesn't inhibit your potential for forward mobility and you might as well go jog outside. I know you took it from somewhere else and it's not your idea, but that doesn't change anything except it's not your idea that's faulty.

[Skyylya]

In what you quoted, I was debating that terminology of calling an elongated moving ground a treadmill, not the concept of if a plane would take off on said moving ground.

read the rest of my posts and you'll see that.

I may have been splitting hairs with that, but I was not wrong in my prediction about the plane taking off.

[Metah]

The plane would generate enough forward thrust to be able to penetrate a wall of diamond Dragonforce, generally regarded as the hardest metal in the world.

[Cheerios]

gonna have to say you weren't...although you said it would fly if the treadmill was an unreasonable length, that's the way the mythbusters tested it so you should be considering it an invalid, pointless test

Jotaru: I'm not taking anything personally, but the fact of the matter is that when you change the size of the treadmill to be anything other than the relative size of the plane it is no longer a 'treadmill' and the concept is no longer valid of if it can fly on a treadmill or not. If you run on a treadmill and set the speed to something that you can moderately run on but still go faster, the size of the treadmill inhibits you from being able to move forward on it, if you took a treadmill and stretched it out 20 feet and set it to the same speed, you could run from one side to the other but what's the point, it's not longer a treadmill because it doesn't inhibit your potential for forward mobility and you might as well go jog outside. I know you took it from somewhere else and it's not your idea, but that doesn't change anything except it's not your idea that's faulty.

If a big treadmill was going backwards at the same speed you were going forward, how would you get from 1 end to another?

[Jotaru]

gonna have to say you weren't...although you said it would fly if the treadmill was an unreasonable length, that's the way the mythbusters tested it so you should be considering it an invalid, pointless test

Yeah, maybe worded a bit poorly, never intended it to be a treadmill as they are. Point in case: an airplane won't even fit on a standard treadmill... so I didn't think it was necessary to point out that wasn't the size it'd be.

If a big treadmill was going backwards at the same speed you were going forward, how would you get from 1 end to another?

Because it just makes the wheels spin, it doesnt counteract any of the forces pulling the plane forward (namely, the jet engines). If you were in a car, you wouldn't move, for that very reason, but since the force is outside, it works.

[Skyylya]

gonna have to say you weren't...although you said it would fly if the treadmill was an unreasonable length, that's the way the mythbusters tested it so you should be considering it an invalid, pointless test

Jotaru: I'm not taking anything personally, but the fact of the matter is that when you change the size of the treadmill to be anything other than the relative size of the plane it is no longer a 'treadmill' and the concept is no longer valid of if it can fly on a treadmill or not. If you run on a treadmill and set the speed to something that you can moderately run on but still go faster, the size of the treadmill inhibits you from being able to move forward on it, if you took a treadmill and stretched it out 20 feet and set it to the same speed, you could run from one side to the other but what's the point, it's not longer a treadmill because it doesn't inhibit your potential for forward mobility and you might as well go jog outside. I know you took it from somewhere else and it's not your idea, but that doesn't change anything except it's not your idea that's faulty.

If a big treadmill was going backwards at the same speed you were going forward, how would you get from 1 end to another?

I said in one or more of my posts in this thread, the force generated by the engine/propellers is completely separate from the wheelbase and therefore does not restrict it's movement.

As I said if you put an RC car on the treadmill like they did in mythbusters, it will sit absolutely still and if you put your hand behind it and push it forward there will be almost no force against you, and you can easily push it forward.

The concept is the same for the engine of the place, it has nothing to do with the wheelspeed, and because of that the plane will still move forward as it should enough so that it can take off.

[ozz]

In what you quoted, I was debating that terminology of calling an elongated moving ground a treadmill, not the concept of if a plane would take off on said moving ground.

read the rest of my posts and you'll see that.

I may have been splitting hairs with that, but I was not wrong in my prediction about the plane taking off.

i read them all before i posted, and i know you said the plane would take on in a situation akin to what the mythbusters presented. i guess what i'm saying is, the guys on tv and jotaru both presented the same problem but you disagreed with their interpretation of the problem. so,if you were asked if a plane on a giant treadmill would takeoff (read: OP) you would say...

Please go back to whereever you found this and tell the people that think it can fly that they are idiots and should spend 45 minutes each day banging their head into a wall.

but if the mythbusters/jotaru were asked that question, they would say it would take off

[Skyylya]

The point that a lot of you are missing, is that friction, wheelspeed, treadmill speed etc.. is all irrelevant.

Ground torque and forward propulsion via jets are two different sources of acceleration. What you all are saying would be true if the jet was moved by torque at the wheelbase and not by a jet propulsion system that has nothing to do with ground contact.

Here's a way to test this, sorta. Take a treadmill and take an RC car. Set the treadmill at a speed that the car can keep up with so that the car is essentially stationary while the engine is providing power to the wheels. Now while that is running, take your hand and push the RC car forward from behind. Regardless of how fast the wheels are going and regardless of the ground conditions under the wheel, you acting as a different source of the movement will still move the RC car forward, the concept is the same for the plane. The wheels will turn at whatever speed the track is going at, but the other source of propulsion will still push the plane forward because it operates independant of the ground.

The ground condition is irrelevant because there is no restriction on the wheels or ground torque to generate forward movement. The force moving the plane comes from the jet propulsion which will move the plane forward regardless of whatever is under it, ground/water/treadmill/air etc...

Jotaru: I'm not taking anything personally, but the fact of the matter is that when you change the size of the treadmill to be anything other than the relative size of the plane it is no longer a 'treadmill' and the concept is no longer valid of if it can fly on a treadmill or not. If you run on a treadmill and set the speed to something that you can moderately run on but still go faster, the size of the treadmill inhibits you from being able to move forward on it, if you took a treadmill and stretched it out 20 feet and set it to the same speed, you could run from one side to the other but what's the point, it's not longer a treadmill because it doesn't inhibit your potential for forward mobility and you might as well go jog outside. I know you took it from somewhere else and it's not your idea, but that doesn't change anything except it's not your idea that's faulty.

I think this post kinda explains what I'm saying. My arguement about what to call a 'treadmill' was kinda stupid and I admit that. Not sure why I was argue such an irrelevant point. But, what I was saying about the principals of flight and the driving force to take off were accurate.


Edit: even in my first response to this thread that you quoted, it was more to the fact that the plane would move forward and therefore would not take off while stationary, because the plane would not remain stationary.

[ozz]

I think this post kinda explains what I'm saying. My arguement about what to call a 'treadmill' was kinda stupid and I admit that. Not sure why I was argue such an irrelevant point.

thats why i said you were wrong...was kinda mad during the thread's initial run tbh because jotaru kept trying to tell you that you were right but said that jotaru was wrong and that making the treadmill long enough for the aircraft to move was defeating the point of the question. everyone knows a stationary plane won't fly, it's not debatable in the least

[Quixotic]

Don't call it a treadmill, I'm pretty sure the original question says its a conveyor belt (same thing more or less). And I've read through the RIDICULOUS debates about this over on other forums (seriously like 30 page long debates), and most people get tricked by the fact that a plane is not powered by its wheels, and that its wheels are on bearings (and even if you did apply the force of friction and what not, I doubt they'd be able to overcome the thousands of lbs of thrust that jet engines generate).

[Khamsin]

Well, it's kind of like a car on ice. Will a car on a perfectly frictionless, polished, flat surface be able to move forward? What if it had a nitro boost? It's probably easier to see what would happen then.

[Skyylya]

I think this post kinda explains what I'm saying. My arguement about what to call a 'treadmill' was kinda stupid and I admit that. Not sure why I was argue such an irrelevant point.

thats why i said you were wrong...was kinda mad during the thread's initial run tbh because jotaru kept trying to tell you that you were right but said that jotaru was wrong and that making the treadmill long enough for the aircraft to move was defeating the point of the question. everyone knows a stationary plane won't fly, it's not debatable in the least

And I can admit that I was off on a tanget in the whole 'what is a treadmill' debate that didn't matter. But for everything I said about the plane itself and whether it would take off is another story, I was right about that.

Either way I was glad to see this, it was cool to see it actually work.

[Lockecole7]

Uggh...I think it's pretty obvious that Skyylya's lack of math concepts (the fact that you didnt understand those simple equations states A LOT) shows through in his realization of how this system would work.

First of all you have to decide on a static situation.

1) You have a treadmill type ground, with no obstructions. This treadmill will always use enough counterforce to equate the spinning of the wheels.
2)Wheelbase spins on its own
3)Wheels spin FASTER due to the jets propulsion.

This where most of you are missing things, and just like what divistheory stated...

I disagree. The parameters were very clearly defined in the original problem. It said specifically that at any point in time t, if the velocity of the plane is v(t), then the velocity of the treadmill is -v(t). As such, the parameters on the speed of the treadmill are as follows:

K > v(t) >= 0

That is that at ANY point the wheel base starts moving faster, (wether its a huge giant pushing it, or a jet propulsion system) all of these things make the wheels move faster, correct? Otherwise if they didnt, it would either A)Be off the ground or B)Moving faster than the speed of the wheels spinning, essentially demolishing them, and causing the plane to crash. Neither of these are possible if the treadmill ground moves at the same speed of the wheelbase. If they were then that would mean the treadmill was not adhering to the parameters that were stated in the OPs, that the speed of both the wheels (REGARDLESS OF THE REASON FOR THEIR SPEED) would always be matched by the ground its on.

If the above was not true, then why even have the treadmill, if at one point it's going to fail in up-keeping the same speed, and essentially be useless. If at any point the plane starts moving forward, the treadmill's purpose in the theory is null and void, and therefore nullifies the whole experiment imo.

Anyone get any of that?

[Quixotic]

People are reading too deep into the parameters imo. Yes, its true that if the treadmill constantly matched velocity of the plane, then the bearings would probably just melt and the plane would crash, but the overall idea is that the conveyorbelt/treadmill cannot restrict the plane from flying. My knowledge of physics is very hazy nowadays, but I'm pretty sure if you drew force diagrams on the system, it'd show that the treadmill has no real effect on the body of the plane because of how free spinning wheels work (the treadmill acts on the wheels, but the wheels aren't necessarily part of the body of the plane), while the plane is obviously being pushed by the force of the jet engines.

[Jotaru]

jotaru was wrong and that making the treadmill long enough for the aircraft to move was defeating the point of the question. everyone knows a stationary plane won't fly, it's not debatable in the least

So we were debating whether an aircraft could fit on a jenny craig treadmill and successfully take off from said miniature platform?

/boggle