Will it Fly?

[Tristam]

The weight of the plane overpowers the engines, that's why it needs to move forward to create lift. Even so, the jets cause a forward velocity in the plane, since the weels are in contact with the plane and the treadmill, and as long as the treadmill maintains the opposite speed of the plane, the plane will not move forward. If the wheels are faulty at high speeds, then they will fail.

I work with physicists and can call some engineers about this, but if they call me an idiot I'm taking it out here lol!

edit: got to it on the internet, someone had a good explanation of why the plane would take off even though the weels turned to molten lava beneath it.

it's here
http://www.boingboing.net/2006/12/11/ai ... ll_pr.html

I guess I just didn't think of the weels as "freewheels". Eventually the jets will cause the wheels to amount to negligible friction, and the plane would move forward while the wheels failed? Either way there are alot of good people talking about it on that thread. Although would the plane take off before the wheels, undercarriage, and wings burst into flames and asplode? Practically, the plane wouldn't take off, theoretically with awesome wheels? Sure

[Khamsin]

Now, imagine a helicopter enclosed completely within a box much much larger than it, but with a pole sticking out the top to prop up the box so it remains in the center of it.

Can it fly?!

What if it had an angled floor (an upside-down V shape, like this: /\ ), instead of a flat one, such that the downward thrust of the helicopter was split up and reflected outward equally to both sides?

[ozz]

There is counter-motion in the treadmill so the plane isn't really moving forward. If it's not moving forward it's not creating friction. If it's not creating friction, air isn't being pushed over its wings. If air isn't being pushed over its wings, it can't take off.

Seriously, for a simpler version of this... go running outside and feel the air pushing past your face. Then go run on a treadmill. You'll see significantly less air pushing on your face, if any at all, since the treadmill is counterbalancing your forward motion.

you're not understanding the point...say the plane goes 100mph at full power
if the plane is at full power on the tread-way,and the ground is moving in an opposite direction at 100mph,the plane is still going to be moving very fast relative to the non-treadmill ground,and the air...say,99mph,because the treadmill exerts very little force onto the plane.

as to your example on running on a treadmill,that would apply if the plane was being propelled by a force exerted on the wheels,but it's not. its being exerted by skyyla's pusher-guy standing on stationary ground,making your experience the air pushing on your face since you're moving forward relative to stationary ground.

the air the jets push isnt effected by the treadmill,so it lets the plane gain velocity relative to the earth

[Kaylia]

Dammit, was gonna photoshop a big fan in front of the wings, but couldnt find any fan picture on the side >_>

[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.

[Jotaru]

^^; Except, as you I keep reminding you and you keep skipping over, nobody ever said it was the size of a conventional treadmill. 8) The idea was to work with a ground that is moving against you, so the treadmill was used to explain the ground movement. The idea wasn't to limit the movement of the airplane via handlebars / any other stuff. Reread OP, its a runway.

[Tristam]

Skyyla: I think you're right, but just cuz' I'm still wrapping my head around this, for the RC car, you'd push it and the treadmill would speed up because your force caused the car to move faster? Eventually, you'd push it so hard that you overcame the force of friction between the car and the treadmill and THEN it would move forward correct? Just wanna make sure I'm not missing something.

[divisortheory]

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 can't understand why you keep dwelling on the length of the treadmill. The treadmill analogy was used to model a moving piece of ground, don't make it more complicated than it is. I find it utterly ridiculous that we're sitting here dwelling on how it's not possible to have a moving treadmill that's 10 miles long, yet it's perfectly ok to say "assume a plane is sitting on a treadmill trying to take off"

[Skyylya]

^^; Except, as you I keep reminding you and you keep skipping over, nobody ever said it was the size of a conventional treadmill. 8) The idea was to work with a ground that is moving against you, so the treadmill was used to explain the ground movement. The idea wasn't to limit the movement of the airplane via handlebars / any other stuff. Reread OP, its a runway.

I understand that, I haven't deny'd that a plane can take off of a ground that is moving counter to the planes propulsion as the ground is irrelevant. Just take the term treadmill out and we can all be happy, cause that implies a different construct. Just simply say could a plane take off if it was on a surface that was moving counter to the direction of the jets propulsion system.


In the case of an RC car on a treadmill. The situation is different because the force of the car is being applied directly to the wheels by the cars engine, however the concept is similar. The car itself would be able to remain stationary on the track even though the cars engine is providing acceleration and torque to the wheels in order to move it faster. Theoretically speaking and assuming that the track speed stayed equal to the wheel speed at all times, the car would not go anywhere because all of the acceleration is being applied at the wheelbase.

If you were to then push the vehicle from behind, it would be able to move forward on the track regardless of whatever torque is at the wheelbase because your force would be operating independantly of the wheels. Perhaps a better explanation would be, assume that the treadmill track was providing all of the power, and the car was in neutral and the wheels were reacting to the treadmills power instead of moving under the power of the cars engine. The car would still remain stationary. If you still then pushed the vehicle (or even pulled it if you wanna argue propeller vs. jet propulsion) the car would be able to move on the track regardless of it's wheel speed.

On this same basic subject. Why can't a car fly if you attach wings to it's side? Planes can fly at lower speeds of around 150-200 mph, speeds that cars are capable of. They can't fly because they lose their motility once the wheels leave the ground. There would no longer be anything to push the vehicle forward. The difference on a plane is that it's wheels contact to the ground has no bearing on it's ability to move forward, so whatever speed the wheels are moving at is irrelevant. The plane moves forward because the jets are pushing the vehicle.

[Saga]

Skyyla: I think you're right, but just cuz' I'm still wrapping my head around this, for the RC car, you'd push it and the treadmill would speed up because your force caused the car to move faster? Eventually, you'd push it so hard that you overcame the force of friction between the car and the treadmill and THEN it would move forward correct? Just wanna make sure I'm not missing something.

No, because no matter how much you push it the treadmill is still going to counteract that force by going however fast the car is going in the opposite direction.

[Tristam]

Skyyla: I think you're right, but just cuz' I'm still wrapping my head around this, for the RC car, you'd push it and the treadmill would speed up because your force caused the car to move faster? Eventually, you'd push it so hard that you overcame the force of friction between the car and the treadmill and THEN it would move forward correct? Just wanna make sure I'm not missing something.

No, because no matter how much you push it the treadmill is still going to counteract that force by going however fast the car is going in the opposite direction.

I agree, but only til' you beat friction.

The plane analogy I think is true, as long as you had a perfect bearing between the plane and the wheel. Otherwise after you beat friction, the wheel melts etc. But if you had an indestructable wheel I guess it would be ok. Either way I'm not so good with these theoretical physics problems.

[Jefe]

If the "treadmill" is going backwards at the same speed of the plane, only the planes tires and the "treadmill" have any true speed, the plane will have a speed of 0

No, the plane will have speed (if acceleration is constant then, the acceleration is 0), but I think you meant displacement.

Anyways, since the displacement of the plane is zero, there will not be any force exerted by the air to lift it off the ground.

[divisortheory]

If the "treadmill" is going backwards at the same speed of the plane, only the planes tires and the "treadmill" have any true speed, the plane will have a speed of 0

No, the plane will have speed (if acceleration is constant then, the acceleration is 0), but I think you meant displacement.

Anyways, since the displacement of the plane is zero, there will not be any force exerted by the air to lift it off the ground.

I think we previously established that the displacement of the plane will not be 0.

[Mysterio]

Can a plane land on a treadmill as well?

thats the real question, lol

[Jefe]

If the "treadmill" is going backwards at the same speed of the plane, only the planes tires and the "treadmill" have any true speed, the plane will have a speed of 0

No, the plane will have speed (if acceleration is constant then, the acceleration is 0), but I think you meant displacement.

Anyways, since the displacement of the plane is zero, there will not be any force exerted by the air to lift it off the ground.

I think we previously established that the displacement of the plane will not be 0.

How can it not be zero? Even if it moved, and ended in the same place, displacement is still zero. For instance, let's assume the plane takes off from LAX and arrives in JFK in NY, then it comes back from JFK to LAX, the displacement is still zero... Either I slept in my physics class, or missed some of the "conditions" set by the OP.

[Tristam]

Does this thread remind anyone else of the Monty Hall Problem thread?

[Skyylya]

I just don't know what else to say.

In a realistic world the plane could take off because it's propulsion could overpower whatever speed the treadmill like ground was going at every time. In an unrealistic world where the treadmill-ground has no constraints what-so-ever then who cares it's no longer a good discussion but a what if discussion.

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.

[divisortheory]

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.

[Flarega]

just kinda a theoretical question because I know some people like to sit and ponder relatively impossible situations (myself included) and its a bit of fun brainwork if you're bored.

[thestalkmore]

No, but will it blend?

I thought of this as soon as I saw the topic title lol.