Airplane on a Conveyor conundrum

[Apache]

You two seem to be argueing against no-one.

Not sure where the amount of wheels come into it, or whether they rotate or not.

My original argument against came because I had made the assumtion that the planes speed (not thrust or anything else, just its speed) was relative to the conveyor (or if you like, the ground speed is always the opposite of the aeroplanes speed, so there is never any airspeed), and so fixed in relation to a fixed point outside of the conveyor.

Your assumption is that the planes speed is relative to a fixed point outside of the conveyor, and thus variable. In this case, the conveyor may as well be cancelled out as it has no effect other than a tiny frictional effect on the planes wheels.

Using you assumption, the plane flies as there is a net difference in speed ref. the conveyor.

Using my assumption, there is never a net difference in speed so the plane doesn't fly.

As I said many posts ago, the answer (as in most science) depends on what assuptions you make in the first instance.

Ahhhh, 'popular' science. Nothing like not defining all of the variables properly in the first instance is there?

[Slugsie]

OK, I'm going to make one last serious post here.

Yes, there was a degree of ambiguity in the original question... what is the aircrafts speed measured relative to?

There are two possibilities:

1. The fixed static ground. In which case if the aircraft attains a speed of 50mph, then it is moving at 50mph relative to the ground (and the air - it's still air) so the wings will be generating lift, so it will be able to fly (assuming this particular aircraft has a 50mph take-off speed).

2. The moving surface of the conveyor belt. In this situation yes, the aircraft will have zero speed relative to the ground/air and thus no lift. However, there is a problem with this scenario. The only force preventing the aircraft from moving forward is that generated by the internal friction of the wheels/bearings (if the wheels/bearings had no friction, then the aircrafts inertia will tend to make it not want to change speed if no other forces are acting on it). I'm pretty sure that any aircraft can overcome the internal friction of its bearings with the engines running at around idle. So, given that the aircraft is attempting to take off (and thus its engines are running at nearly maximum) it will have no problem overcoming the friction of the wheels/bearings, and still manage to move through the air and generate lift. I will grant that you may end up with the situation that the conveyor will want to run at ridiculous speeds in order to counteract this, but it is constrained to run at the same speed as the aircraft. The worst that could happen is that you overload the wheels/bearings, and they disintegrate - but that is also a possibility for a normal take-off so you can't really use it here.

There are other problems with scenario 2 that just make trying to get it to work (or not) harder. The main one being that how can the aircraft move its self against the conveyor given that the only thing the aircraft can push against is the air. Another one is, if the aircraft is apparently not moving (relative to the fixed ground) where exactly is the thrust of its engines going? It's not going into the conveyor, as the free spinning wheels of an aircraft mean that there is no mechanism by which this can happen. So, because of the laws of motion (every action having an equal and opposite reaction) the air being thrust out of the back of the engines, must be forcing the aircraft forward.

My basic contention is that you could never actually get scenario 2 to do anything, because it just doesn't work. Therefore, even though it was never explicitly stated originally (I did add a clarification later on) when you work the problem through, you have to work on the basis that the aircrafts speed is measured relative to the fixed ground.

****

BTW, why are you all calling for this thread to be locked? Are people so afraid of healthy intellectual debate that it must be beaten down? Like pretty much all threads, this one will die a natural death when its time comes. Until then if you can't face the discussion any more, then just don't come back.

[Apache]

I cant face the discussion anymore - I'm off to talk about spammers or newbies...

[MattF]

Jeez, don't some get cranky. Simple point. Fixed ground reference point means both cancel each other out. Wheels or any other ancillaries are irrelevant. A fixed reference is a fixed reference, regardless of size/rotation ratios. It can't take off. Simple as. Unless it is a jumpjet, of course.

[KERRSURF]

You two seem to be argueing against no-one.

Just the 22 who seem to think the plane won't fly, and yes I do understand the point about the ambiguity of the question but our assumptions led os down different paths.

"If you assume you make an ass of you and me" can't remember who first said it but it does ring true.

[darkdezigns]

lololol this is so funny,ps im one of the 22 and i stand by it,guess that makes me slow eh yoshie lolol

[yoshie]

lololol this is so funny,ps im one of the 22 and i stand by it,guess that makes me slow eh yoshie lolol

yep

[yoshie]

My original argument against came because I had made the assumtion that the planes speed (not thrust or anything else, just its speed) was relative to the conveyor (or if you like, the ground speed is always the opposite of the aeroplanes speed, so there is never any airspeed), and so fixed in relation to a fixed point outside of the conveyor.

Your assumption is that the planes speed is relative to a fixed point outside of the conveyor, and thus variable. In this case, the conveyor may as well be cancelled out as it has no effect other than a tiny frictional effect on the planes wheels.

Using you assumption, the plane flies as there is a net difference in speed ref. the conveyor.

Using my assumption, there is never a net difference in speed so the plane doesn't fly.

As I said many posts ago, the answer (as in most science) depends on what assuptions you make in the first instance.

Ahhhh, 'popular' science. Nothing like not defining all of the variables properly in the first instance is there?

Yes mate the assumptions made would effect the result

Jeez, don't some get cranky. Simple point. Fixed ground reference point means both cancel each other out. Wheels or any other ancillaries are irrelevant. A fixed reference is a fixed reference, regardless of size/rotation ratios. It can't take off. Simple as. Unless it is a jumpjet, of course.

This fixed point ground referance was never in the original question

The reality can't be argued against thou a plane sat on a moving conveyor
would move forward as the thrust is not dependant on driven wheels against the moving / matching surface.

It was an enjoyable and frutrating thread all at the same time beats
Billy threads thou

[The Kid]

Looking at this simply (it's what I do Best!):

The speed of the wheels on the plane is irrelevant to whether or not it will fly
except that, as the wheels are touching the conveyor belt their speed has an effect on the speed that the conveyor belt runs.

As the conveyor belt is computer controlled there will therefore be a slight delay before it registers an increase in wheel speed and reacts.

The plane will thus actualy move forward slightly, relative to it's position on the conveyor belt, during this delay time.

If it has sufficient fuel, eventually it will reach a high enough speed to generate lift and will therefore be able to take off.

I think

Ken

PS
If the operating system on the computer is Vista then, of course, both the computer and the plane will both crash!

[yoshie]

Looking at this simply (it's what I do Best!):

The speed of the wheels on the plane is irrelevant to whether or not it will fly
except that, as the wheels are touching the conveyor belt their speed has an effect on the speed that the conveyor belt runs.

As the conveyor belt is computer controlled there will therefore be a slight delay before it registers an increase in wheel speed and reacts.

The plane will thus actualy move forward slightly, relative to it's position on the conveyor belt, during this delay time.

If it has sufficient fuel, eventually it will reach a high enough speed to generate lift and will therefore be able to take off.

I think

Ken

PS
If the operating system on the computer is Vista then, of course, both the computer and the plane will both crash!

You were doing well up till this point

[darkdezigns]

yep

ty so kind,but everything else aside u need air at speed passing over and under the wings for lift,where will this come from exactly?

[logey79]

i just rang my mate at NASA (and before woodzie or mattf or anyone else asks - yes it is the same guy who discovered my alien background).

he said that the plane would fly but only if the stewardesses were all naked and the cd player was playing Fuel by Metallica.

so, there you have it.

[yoshie]

ty so kind,but everything else aside u need air at speed passing over and under the wings for lift,where will this come from exactly?

see posts 96 134 135 its no hard ffs

[KERRSURF]

ty so kind,but everything else aside u need air at speed passing over and under the wings for lift,where will this come from exactly?

the plane will move forward! it will pass air over and under the wings!

what is it about this you cannot grasp!

the conveyor will have no effect on this as the plane does not need to power it's wheels to move!

ffs

[KERRSURF]

right bollox, I'm done with this thread.