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Yes..... Physics Vol 3

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By *ralbisw OP Man over a year ago

Exeter

This is going to annoy some but I do not think we have really concluded the problem!!

So to kick off Vol 3 (which is more than threads about Trump)

It will take off!!!!!!!!

In my humble opinion

Sorry all!!!!

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By (user no longer on site) over a year ago

Not read all of the last one but, where is the upwards thrust coming from to lift the wings?

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By *avrick15Man over a year ago

glasgow

"This is going to annoy some but I do not think we have really concluded the problem!!

So to kick off Vol 3 (which is more than threads about Trump)

It will take off!!!!!!!!

In my humble opinion

Sorry all!!!!"

You bastard!!!! Lol

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By *inky-MinxWoman over a year ago

Grantham

"Not read all of the last one but, where is the upwards thrust coming from to lift the wings?"

There isn't any because the plane is sitting completely still

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By *avrick15Man over a year ago

glasgow

"Not read all of the last one but, where is the upwards thrust coming from to lift the wings?"

Don't get involved man it will consume your soul

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By (user no longer on site) over a year ago

Don;t understand why there's even a discussion about it? Title is physics....yet basic physics dictates no forward momentum: no upwards thrust.....not that complicated!

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By (user no longer on site) over a year ago

As has been explained countless times....what the conveyor belt is doing is irrelevant

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By *ensualtouch15Man over a year ago

ashby de la zouch

"Not read all of the last one but, where is the upwards thrust coming from to lift the wings?

There isn't any because the plane is sitting completely still

Wrong again

In the OP we are told the plane is moving

I am amazed

Seems we need to draw a picture

First level is ground . For this we shall say not moving

Second level is moving surface moving backwards let's say at 100 kph

Third level is a wheel attached to an under carriage and the brakes are off , it can spin freely touching the moving surface . The wheel has a circumference of 1 meter

The undercarriage is tethered to the ground

The wheel is now rotating at 1666 rpm however it's speed relative to the ground is 0 kph

The drag on the undercarriage from the moving surface is about 100 pounds

Attached to the undercarriage is a jet engine that can push at 100 000 pounds

Set the engine to produce 100 pounds thrust

The carriage stays still

Reduce the thrust the undercarriage follows the direction of the moving surface

Increase the thrust to 50 000 pounds and the carriage accelerates forward bringing it's wheels forwards relative to the ground , the moving surface and most importantly the air mass

The only equation that is relevant here is

Acceleration equals mass divided by force

Thus as long as the force on the undercarriage is less than that of the engine the plane accelerates

As wheels are attached to bearings and designed to reduce drag and no where is it suggested the brake would be applied

It seems many are thinking that with the moving runway it is being suggested the plane does not need to move forward but can stand still and fly , some one mentioned why have long run ways if a conveyer would work lol lol

This is a misunderstanding the plane still needs to move forwards relative to both ground and air mass , it's just the moving runway has no influence upon this action it just rolls forward , it's wheels move forward at the planes speed, BUT rotate at twice the rpm

Gosh simple physics

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By *avrick15Man over a year ago

glasgow

"Don;t understand why there's even a discussion about it? Title is physics....yet basic physics dictates no forward momentum: no upwards thrust.....not that complicated! "

Look at the last post on the previous thread, clearly another person with physics knowledge

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By (user no longer on site) over a year ago

It depends on the integrity of the experiment. It can't and it won't if the engines are used simply to keep the plane in the same position. It can and it will if the engines are used to match the speed of the conveyor belt.

I read that on t'interweb and understood it but couldn't possibly explain it cos I'm not a physicist and it made my head hurt.

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By *ensualtouch15Man over a year ago

ashby de la zouch

"Don;t understand why there's even a discussion about it? Title is physics....yet basic physics dictates no forward momentum: no upwards thrust.....not that complicated! "

There is lots of forward motion and the belt does not counter this in any way

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By (user no longer on site) over a year ago

Hmm I read the original post and there's no mention of being tethered to the ground or jet propulsion......?

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By (user no longer on site) over a year ago

If you're taking it extremes...

How fast will the treadmill need to go for the wheels to generate sufficient wind to cause the plane to lift?

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By *ensualtouch15Man over a year ago

ashby de la zouch

"Hmm I read the original post and there's no mention of being tethered to the ground or jet propulsion......?"

It's a plane ? They are usually propelled by a spinning air screw ?

The tether was only a visual aid to show the wheels spinning and plane stationary

Try it the other way the moving surface drags the plane back at 100 mph would need to be a long moving surface , in this case the wheels are not rotating but moving backwards at 100 mph

Now start plane propulsion system the plane will first slow down and then move forward exactly as any normal runway as regardless of any movment of the surface beneath

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By (user no longer on site) over a year ago

It will take off

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By *aucy tiggerWoman over a year ago

Back where I belong

Abandon hope all ye who post on here xx

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By *ohnaronMan over a year ago

london

"Don;t understand why there's even a discussion about it? Title is physics....yet basic physics dictates no forward momentum: no upwards thrust.....not that complicated! "

But you have neglected the ground effect from the moving conveyor.

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By *inky-MinxWoman over a year ago

Grantham

"If you're taking it extremes...

How fast will the treadmill need to go for the wheels to generate sufficient wind to cause the plane to lift?"

I read that the treadmill goes at the same speed as the wheels, but in opposite directions?

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By *inky-MinxWoman over a year ago

Grantham

This thread make me think of that age old statistic; 50% of the population are under average intelligence

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By (user no longer on site) over a year ago

"If you're taking it extremes...

How fast will the treadmill need to go for the wheels to generate sufficient wind to cause the plane to lift?

I read that the treadmill goes at the same speed as the wheels, but in opposite directions?"

Yes but at some point the wheels (and the conveyor for that matter) must generate turbulence. So putting aside that the materials wouldn't hack it in reality... is there a point at which that turbulence would be sufficient to lift the plane?

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By *inky-MinxWoman over a year ago

Grantham

Original post, just for clarification

“A plane is standing on a runway that can move (some sort of band conveyer belt). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?”

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By *ensualtouch15Man over a year ago

ashby de la zouch

"If you're taking it extremes...

How fast will the treadmill need to go for the wheels to generate sufficient wind to cause the plane to lift?

I read that the treadmill goes at the same speed as the wheels, but in opposite directions?"

That's just so misleading

What it's trying to do is compare with a car on a treadmill where the speed can be matched and is measured through its wheels

A plane measures it's speed through the air , it's wheels have no bearing upon anything

So regardless of the treadmill speed as soon as thrust comes from engine the plane and it's wheels will note forward relative to the only important factor here the air mass xx

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By *eliz NelsonMan over a year ago

The Tantric Tea Shop

Aah! But is Tom Cruise flying the plane...I am sure he was pretty top pilot in some film or other and....actually, I'm bored and off to another thread

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By *inky-MinxWoman over a year ago

Grantham

"Aah! But is Tom Cruise flying the plane...I am sure he was pretty top pilot in some film or other and....actually, I'm bored and off to another thread

My Dad was on the design team for that plane

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By (user no longer on site) over a year ago

OK I think there's a difference in interpretation here.

When the question posed is; 'can the plane take off?' Are you taking that to mean, 'how much opposing force will need to be generated in order for it to move forward?'

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By *eliz NelsonMan over a year ago

The Tantric Tea Shop

"Aah! But is Tom Cruise flying the plane...I am sure he was pretty top pilot in some film or other and....actually, I'm bored and off to another thread

My Dad was on the design team for that plane

Ooh! The real plane or the one in the Movie, whatever it was

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By *ohnaronMan over a year ago

london

I believe at least one man powered plane used the ground effect to provide additional lift at take off. Admittedly the wings were near the ground for this effect to be significant but the OP places no restiction on the distance of the wings from the ground.

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By *eliz NelsonMan over a year ago

The Tantric Tea Shop

I also take it, that the areoplane in question is not fro the fleet of Cheesyjet or Lyingair

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By (user no longer on site) over a year ago

"If you're taking it extremes...

How fast will the treadmill need to go for the wheels to generate sufficient wind to cause the plane to lift?

I read that the treadmill goes at the same speed as the wheels, but in opposite directions?

That's just so misleading

What it's trying to do is compare with a car on a treadmill where the speed can be matched and is measured through its wheels

A plane measures it's speed through the air , it's wheels have no bearing upon anything

So regardless of the treadmill speed as soon as thrust comes from engine the plane and it's wheels will note forward relative to the only important factor here the air mass xx"

I get that. It's been explained to death several times over.

But as people are ignoring reality... my hypothesis is worthy.

At what point will that sufficient air mass be generated via the wheels & conveyor?

Or to put it more simply - yes the fucking plane will take off one way or an other eventually

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By *ohnaronMan over a year ago

london

An interesting point - when the conveyor belt goes super-sonic in which ditection will the principal shock wave propergate?

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By *ensualtouch15Man over a year ago

ashby de la zouch

"I believe at least one man powered plane used the ground effect to provide additional lift at take off. Admittedly the wings were near the ground for this effect to be significant but the OP places no restiction on the distance of the wings from the ground."

Ok seems two questions have formed from one

OK the plane is the the moving platform

The turbine produces a tiny amount of thrust to perfectly equal the tredmill drag

The plane stands still

As the treadmill increases speed the thrust is adjusted ever ever so slightly to match a still extremely small force

The plane relative to air mass is static

The plane does not fly

The engine is then allowed to power up vastly exceeding any plausible drag effect from moving runway , the plane accelerates through the air mass and takes off

Third , if plane was tiny let's say 20 grams and the belt was wide ridged and moving fucking fast, the plane could indeed lift off from the draft

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By *unandbuckCouple over a year ago

Sheffield

Mavrik

Just wanted to pick up from pt2 and your kind compliments on my post and your admiration of my nice ass. Thanks gorgeous

Mr B

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By (user no longer on site) over a year ago

" Third , if plane was tiny let's say 20 grams and the belt was wide ridged and moving fucking fast, the plane could indeed lift off from the draft "

I want to see this - this sounds ace

Anyone have a really big treadmill and a free weekend?

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By *ohnaronMan over a year ago

london

Ok seems two questions have formed from one

OK the plane is the the moving platform

The turbine produces a tiny amount of thrust to perfectly equal the tredmill drag

The plane stands still

As the treadmill increases speed the thrust is adjusted ever ever so slightly to match a still extremely small force

The plane relative to air mass is static

The plane does not fly

The engine is then allowed to power up vastly exceeding any plausible drag effect from moving runway , the plane accelerates through the air mass and takes off

Third , if plane was tiny let's say 20 grams and the belt was wide ridged and moving fucking fast, the plane could indeed lift off from the draft "

Well said.

May I ad the OP makes no observation about possibility of plane taking off backwards (perhaps I should fly this cannard elsewhere (joke)).

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By *unandbuckCouple over a year ago

Sheffield

I think by now everybody except one or two knows the plane will fly.

For those that still don't believe it watch the mybusters youtube clip in pt2.

Beyond that I cant explain it any more different ways.

There is a 'does god exist' thread running now that should be less controversial than this one

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By *avrick15Man over a year ago

glasgow

"Mavrik

Just wanted to pick up from pt2 and your kind compliments on my post and your admiration of my nice ass. Thanks gorgeous

Mr B

You're welcome and I'm staying with the bum on this one!!! Lol

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By *avrick15Man over a year ago

glasgow

"I think by now everybody except one or two knows the plane will fly.

For those that still don't believe it watch the mybusters youtube clip in pt2.

Beyond that I cant explain it any more different ways.

There is a 'does god exist' thread running now that should be less controversial than this one

Fck I'm on that one too...

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By *eliz NelsonMan over a year ago

The Tantric Tea Shop

"I think by now everybody except one or two knows the plane will fly.

For those that still don't believe it watch the mybusters youtube clip in pt2.

Beyond that I cant explain it any more different ways.

There is a 'does god exist' thread running now that should be less controversial than this one

Did God make the plane fly

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By *unandbuckCouple over a year ago

Sheffield

"Mavrik

Just wanted to pick up from pt2 and your kind compliments on my post and your admiration of my nice ass. Thanks gorgeous

Mr B

You're welcome and I'm staying with the bum on this one!!! Lol "

Did you notice this is Mister B ???

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By (user no longer on site) over a year ago

"I think by now everybody except one or two knows the plane will fly.

For those that still don't believe it watch the mybusters youtube clip in pt2.

Beyond that I cant explain it any more different ways.

There is a 'does god exist' thread running now that should be less controversial than this one

Did God make the plane fly

He's the bastard operating the treadmill.

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By *unandbuckCouple over a year ago

Sheffield

Did God make the plane fly

Well, only God could stop it flying, the belt can't

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By *eliz NelsonMan over a year ago

The Tantric Tea Shop

"I think by now everybody except one or two knows the plane will fly.

For those that still don't believe it watch the mybusters youtube clip in pt2.

Beyond that I cant explain it any more different ways.

There is a 'does god exist' thread running now that should be less controversial than this one

Did God make the plane fly

He's the bastard operating the treadmill."

Thats open to conjecture....heeeere we go

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By *avrick15Man over a year ago

glasgow

"Mavrik

Just wanted to pick up from pt2 and your kind compliments on my post and your admiration of my nice ass. Thanks gorgeous

Mr B

You're welcome and I'm staying with the bum on this one!!! Lol

Did you notice this is Mister B ???"

I did lol but of course I was admiring your good lady with your permission of course... I'm sure you have a lovely bum too but that's not my forte

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By *unandbuckCouple over a year ago

Sheffield

I did lol but of course I was admiring your good lady with your permission of course... I'm sure you have a lovely bum too but that's not my forte

Neither is Physics !

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By *avrick15Man over a year ago

glasgow

I did lol but of course I was admiring your good lady with your permission of course... I'm sure you have a lovely bum too but that's not my forte

Neither is Physics !"

Touché but ''tis physical

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By (user no longer on site) over a year ago

"I think by now everybody except one or two knows the plane will fly.

For those that still don't believe it watch the mybusters youtube clip in pt2.

Beyond that I cant explain it any more different ways.

There is a 'does god exist' thread running now that should be less controversial than this one

Did God make the plane fly

He's the bastard operating the treadmill.

Thats open to conjecture....heeeere we go

He's also a she. I regularly tell him to go fuck himself. And let's face it if you were a god, well why not.

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By *inky-MinxWoman over a year ago

Grantham

"Aah! But is Tom Cruise flying the plane...I am sure he was pretty top pilot in some film or other and....actually, I'm bored and off to another thread

My Dad was on the design team for that plane

Ooh! The real plane or the one in the Movie, whatever it was"

The real one that was also in the movie, the F14 Tomcat

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By *inky-MinxWoman over a year ago

Grantham

"An interesting point - when the conveyor belt goes super-sonic in which ditection will the principal shock wave propergate? "

Throughout the forums?

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By *inky-MinxWoman over a year ago

Grantham

"I think by now everybody except one or two knows the plane will fly."

More than that, I say it won't and I asked my Dad

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By *avrick15Man over a year ago

glasgow

"Aah! But is Tom Cruise flying the plane...I am sure he was pretty top pilot in some film or other and....actually, I'm bored and off to another thread

My Dad was on the design team for that plane

Ooh! The real plane or the one in the Movie, whatever it was

The real one that was also in the movie, the F14 Tomcat

And I'm maverick... say hi to your dad for me

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By *inky-MinxWoman over a year ago

Grantham

"Aah! But is Tom Cruise flying the plane...I am sure he was pretty top pilot in some film or other and....actually, I'm bored and off to another thread

My Dad was on the design team for that plane

Ooh! The real plane or the one in the Movie, whatever it was

The real one that was also in the movie, the F14 Tomcat

And I'm maverick... say hi to your dad for me

Oh yeah, I'll need a really really good cover story

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By *ee VianteWoman over a year ago

Somewhere in North Norfolk

And still nobody has read the XKCD blog post

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By *unandbuckCouple over a year ago

Sheffield

"I think by now everybody except one or two knows the plane will fly.

More than that, I say it won't and I asked my Dad

What? I thought you were a 'it will move and fly' ?

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By (user no longer on site) over a year ago

"And still nobody has read the XKCD blog post

The what now?

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By (user no longer on site) over a year ago

Whoosh

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By (user no longer on site) over a year ago

What's goes up must come down.

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By *ohnaronMan over a year ago

london

"What's goes up must come down. "

Knickers

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By *ee VianteWoman over a year ago

Somewhere in North Norfolk

"And still nobody has read the XKCD blog post

The what now?"

I mentioned it a couple of times on thread 2.

I can't post a link but it's called "The Goddamn Airplane on the Goddamn Treadmill" and is a blog post on XKCD. It'll be simple enough to find.

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By *unandbuckCouple over a year ago

Sheffield

"And still nobody has read the XKCD blog post

The what now?

I mentioned it a couple of times on thread 2.

I can't post a link but it's called "The Goddamn Airplane on the Goddamn Treadmill" and is a blog post on XKCD. It'll be simple enough to find."

But those threads are longer than ours!

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By *ee VianteWoman over a year ago

Somewhere in North Norfolk

"And still nobody has read the XKCD blog post

The what now?

I mentioned it a couple of times on thread 2.

I can't post a link but it's called "The Goddamn Airplane on the Goddamn Treadmill" and is a blog post on XKCD. It'll be simple enough to find.

But those threads are longer than ours!"

Not a thread, a blog post. It's not that long.

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By (user no longer on site) over a year ago

"And still nobody has read the XKCD blog post

The what now?

I mentioned it a couple of times on thread 2.

I can't post a link but it's called "The Goddamn Airplane on the Goddamn Treadmill" and is a blog post on XKCD. It'll be simple enough to find.

But those threads are longer than ours!

Not a thread, a blog post. It's not that long."

Think that's enough for me. I kinda took a step back and thought "what am i doing talking about aerodynamics on a swingers site!".....it's no wonder I never get laid! :P

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By *unandbuckCouple over a year ago

Sheffield

"And still nobody has read the XKCD blog post

The what now?

I mentioned it a couple of times on thread 2.

I can't post a link but it's called "The Goddamn Airplane on the Goddamn Treadmill" and is a blog post on XKCD. It'll be simple enough to find.

But those threads are longer than ours!

Not a thread, a blog post. It's not that long."

I've just read it and am in #2 camp. But I think most of the 'it wont fly' posters previously, were actually 'I dont actually get any of it' . I might be being unfair and am sure some were #3 .

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By *orwegian BlueMan over a year ago

Iceland, but Aldi is closer..

I ran this past a room of physicists with a combined Iq greater than the mass of a black hole..

They also design things that go whizz, so know a little bit about this kinda stuff..

I read them the text from the original post..

The instant and unanimous response Was it couldn't take off, followed by fits of giggles that I didn't know the answer to a question so simple!!!

So any credibility as a dynamacist I have now lost with the senior scientists I work with, so thanks Op...

but the answer was conclusive..

Apparently it is to do with Newton's first and second laws only..

It still makes no sense to me, it should be able to take off..

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By *avrick15Man over a year ago

glasgow

"I ran this past a room of physicists with a combined Iq greater than the mass of a black hole..

They also design things that go whizz, so know a little bit about this kinda stuff..

I read them the text from the original post..

The instant and unanimous response Was it couldn't take off, followed by fits of giggles that I didn't know the answer to a question so simple!!!

So any credibility as a dynamacist I have now lost with the senior scientists I work with, so thanks Op...

but the answer was conclusive..

Apparently it is to do with Newton's first and second laws only..

It still makes no sense to me, it should be able to take off..

Thank god... oh hang on I mean a non existent entity that gives thanks selflessly

And rest....

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By *ee VianteWoman over a year ago

Somewhere in North Norfolk

And still!

Unbelievable!

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By (user no longer on site) over a year ago

Well Ive just got off the blower with my mate Dave over at the large hadron collider. he said haven't you lot got anything better to do on a website full of people looking to get laid

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By *ohnaronMan over a year ago

london

"I ran this past a room of physicists with a combined Iq greater than the mass of a black hole..

They also design things that go whizz, so know a little bit about this kinda stuff..

I read them the text from the original post..

The instant and unanimous response Was it couldn't take off, followed by fits of giggles that I didn't know the answer to a question so simple!!!

So any credibility as a dynamacist I have now lost with the senior scientists I work with, so thanks Op...

but the answer was conclusive..

Apparently it is to do with Newton's first and second laws only..

It still makes no sense to me, it should be able to take off..

That their response was instant says a lot. The subtleties of the question have eluded them. I assume they have found secure jobs that will lead to a pension.

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By *ommenhimCouple over a year ago

wigan

"If you're taking it extremes...

How fast will the treadmill need to go for the wheels to generate sufficient wind to cause the plane to lift?

I read that the treadmill goes at the same speed as the wheels, but in opposite directions?

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By *avrick15Man over a year ago

glasgow

"Well Ive just got off the blower with my mate Dave over at the large hadron collider. he said haven't you lot got anything better to do on a website full of people looking to get laid "

lol this is mental foreplay

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By *ee VianteWoman over a year ago

Somewhere in North Norfolk

I'm seeing why certain other sites have banned the question!

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By *ohnaronMan over a year ago

london

"If you're taking it extremes...

How fast will the treadmill need to go for the wheels to generate sufficient wind to cause the plane to lift?

I read that the treadmill goes at the same speed as the wheels, but in opposite directions?

No"

Depending on circumstances - yes. Ground effect.

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By (user no longer on site) over a year ago

"Well Ive just got off the blower with my mate Dave over at the large hadron collider. he said haven't you lot got anything better to do on a website full of people looking to get laid

lol this is mental foreplay

Well we could at least discuss something worthwhile like ohms law

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By (user no longer on site) over a year ago

"Not read all of the last one but, where is the upwards thrust coming from to lift the wings?

There isn't any because the plane is sitting completely still

Wrong again

In the OP we are told the plane is moving

I am amazed

Seems we need to draw a picture

First level is ground . For this we shall say not moving

Second level is moving surface moving backwards let's say at 100 kph

Third level is a wheel attached to an under carriage and the brakes are off , it can spin freely touching the moving surface . The wheel has a circumference of 1 meter

The undercarriage is tethered to the ground

The wheel is now rotating at 1666 rpm however it's speed relative to the ground is 0 kph

The drag on the undercarriage from the moving surface is about 100 pounds

Attached to the undercarriage is a jet engine that can push at 100 000 pounds

Set the engine to produce 100 pounds thrust

The carriage stays still

Reduce the thrust the undercarriage follows the direction of the moving surface

Increase the thrust to 50 000 pounds and the carriage accelerates forward bringing it's wheels forwards relative to the ground , the moving surface and most importantly the air mass

The only equation that is relevant here is

Acceleration equals mass divided by force

Thus as long as the force on the undercarriage is less than that of the engine the plane accelerates

As wheels are attached to bearings and designed to reduce drag and no where is it suggested the brake would be applied

Gosh simple physics

the undercarriage is tethered to the ground you say? then it's probably not going anywhere.

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By *ohnaronMan over a year ago

london

"Well Ive just got off the blower with my mate Dave over at the large hadron collider. he said haven't you lot got anything better to do on a website full of people looking to get laid

lol this is mental foreplay

Well we could at least discuss something worthwhile like ohms law

Are people with metal plates in their heads allowed to work on the LHC?

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By *ohnaronMan over a year ago

london

"Well Ive just got off the blower with my mate Dave over at the large hadron collider. he said haven't you lot got anything better to do on a website full of people looking to get laid "

Ask him why the Higgs field has got it in for fat birds?

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By (user no longer on site) over a year ago

It's a plane chartered by Southern Rail so the air crew are on strike and the passengers sit like lemons on board with the plane going nowhere! No-one knows how to switch on the engines or the runway belt!

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By (user no longer on site) over a year ago

Then the aircraft faces a 250mph headwind. It lifts vertically!

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By (user no longer on site) over a year ago

It's a plane for Buzz airways! It gets taken down by a SWAT team!

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By *avrick15Man over a year ago

glasgow

"Well Ive just got off the blower with my mate Dave over at the large hadron collider. he said haven't you lot got anything better to do on a website full of people looking to get laid

lol this is mental foreplay

Well we could at least discuss something worthwhile like ohms law

Ok sure Oh my god you look gorgeous bent over in those pics

hubba

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By (user no longer on site) over a year ago

Then along comes a Virgin Atlantic plane! You know the big blue ocean thing! Ok, yeah, I know none of you understand the other word!

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By *oo hotCouple over a year ago

North West

It is not even complicated.

No movement of air across the wings means no lift.

End of story.

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By *oncupiscentTonyMan over a year ago

Kent

"It is not even complicated.

No movement of air across the wings means no lift.

End of story."

Oh Christ not another one ffs, so what is the prop doing then!?

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By *enard ArgenteMan over a year ago

London and France

[Removed by poster at 19/11/16 08:11:54]

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By *enard ArgenteMan over a year ago

London and France

The prop is providing thrust ( as does a jet engine) do you think that aircraft lift is generated by the propeller " blowing air over the wings?"

If so, then jet aircraft can't fly as the jets don't " blow air over the wings"

Neither can a rocket powered aircraft

Or an aircraft with the propeller at the back ( "pusher-prop").

The prop/ jet/ rocket pushes the plane forward; as soon as the plane has enough speed relative to the surrounding air, the airflow over the wings creates lift.

The only way that the pjane doesn't take off, is if the pilot collides with the treadmill operator to ensure that he only applies enough thrust to overcome the friction in the wheel bearings.

Or if you reinterpret the question such that the treadmill and the planes wheels must always ( instantaneously) match each other; if you start with the wheels and the treadmill stationary, then nothing happens at all; they must both match each other; if neither is moving, then neither will change, and, according to that interpretation, there is no way that you can put anything into the system, it is a constant state, the wheels and treadmill are matched ( not moving or rotating at all) and logic demands that nothing happens at all. You don't even turn the planes engines on.

The whole thing is simply a logics thought experiment, designed to make people interpret it different ways; depending on your interpretation, you will come up with different ( seemingly logical) answers. The logic demands that you interpret the question.

But there are two unrelated elements of the problem; and the mistake is to relate the two elements together; one element is the treadmill/ wheel conundrum; which is a valid question about control systems, and how instantaneous feedback needs to be to maintain a steady state, the other is simple; if the thrust is applied to a body, and the thrust overcomes inertia and then any frictions, will the body move?

That's it. The airplane and its thrust is one issue, simply solved; the treadmill and wheel issue demonstrates that instantaneous changes to two elements of a system is physically impossible; ( except when a system is in total equilibrium steady state; in which it can never change) and that matching of elements of a system need feedback and then an input to synchronise.

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By *enard ArgenteMan over a year ago

London and France

Collides/ colludes

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By (user no longer on site) over a year ago

I don't think anyone is claiming that if the plane is stationary it can take off. I think everyone agrees that the plane needs airflow over the wings.

(Trying to find some common ground!)

The area to focus on is will the plane move forward?

Clearly if there is an equal and opposite force to the engines which pushes the plane backwards, it won't move.

However the moving band doesn't give that. It only spins the wheels (fast!)

The plane doesn't get pushed along by its wheels. They are free spinning. Therefore there is no opposite force to the engines. The plane will move and take off.

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By *aucy tiggerWoman over a year ago

Back where I belong

I'm enjoying all this talk about thrust so please keep going

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By *enard ArgenteMan over a year ago

London and France

"I don't think anyone is claiming that if the plane is stationary it can take off. I think everyone agrees that the plane needs airflow over the wings.

(Trying to find some common ground!)

The area to focus on is will the plane move forward?

Clearly if there is an equal and opposite force to the engines which pushes the plane backwards, it won't move.

However the moving band doesn't give that. It only spins the wheels (fast!)

The plane doesn't get pushed along by its wheels. They are free spinning. Therefore there is no opposite force to the engines. The plane will move and take off."

Correct

Always

Unless the brakes are on, or there is so much friction in the wheels and bearings that the engines thrust cannot overcome it. ( which in the real world is impossible) But that ends up in a illogical closed loop, because then the wheels won't turn, and since the conveyor belt has to match the wheels, it won't move either, do absolutely nothing happens; the conveyor doesn't move, the wheels don't turn, and the whole problem vanishes in a puff of illogicality.

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By *ait88Man over a year ago

Plymouth

"I don't think anyone is claiming that if the plane is stationary it can take off. I think everyone agrees that the plane needs airflow over the wings.

(Trying to find some common ground!)

The area to focus on is will the plane move forward?

Clearly if there is an equal and opposite force to the engines which pushes the plane backwards, it won't move.

However the moving band doesn't give that. It only spins the wheels (fast!)

The plane doesn't get pushed along by its wheels. They are free spinning. Therefore there is no opposite force to the engines. The plane will move and take off."

The wheels under an aircraft are not by any means free-spinning. There is no way that you could spin just one wheel of even a light aircraft, let alone all of them, or the wheels of a jumbo jet!

The wheels are rammed into the runway / conveyor belt by gravity – the weight of the aircraft. They are “locked-down” very firmly indeed. Go outside and spin one of the front wheels of your car by hand. See what I mean? When the belt moves, the aircraft must move with it. There is no force pushing it along the belt in the opposite direction. It stays still on the belt.

I’ll try again: Put a sheet of paper on a table. Put something with wheels on the paper. Move the paper smoothly, like an aircraft starting to roll forward under power – no sudden jerk. The wheels will remain stationary on the paper. Nothing is pushing or pulling the wheels along on the paper. The weight, gravity, is holding them still.

Yet again: when the belt starts moving, what pushes the aircraft in the OPPOSITE DIRECTION at the same speed if the engine is off? Please, please, please, tell us!

The rate of acceleration of the belt is exactly the same as the rate of acceleration of the aircraft. They move at exactly the same speeds, but in opposite directions. The aircraft it moved backwards by the belt at the same speed that it is moved forwards by the engine. There is no air flow on the wings. They generate no lift. The aircraft cannot fly.

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By *ait88Man over a year ago

Plymouth

And oh yes! An aircraft parked out of doors with its brakes on and wheels chocked can take off if a wind is blowing directly from ahead at a speed which is greater that its take-off speed. But it will need a damned good pilot!

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By *ensualtouch15Man over a year ago

ashby de la zouch

"I ran this past a room of physicists with a combined Iq greater than the mass of a black hole..

They also design things that go whizz, so know a little bit about this kinda stuff..

I read them the text from the original post..

The instant and unanimous response Was it couldn't take off, followed by fits of giggles that I didn't know the answer to a question so simple!!!

So any credibility as a dynamacist I have now lost with the senior scientists I work with, so thanks Op...

but the answer was conclusive..

Apparently it is to do with Newton's first and second laws only..

It still makes no sense to me, it should be able to take off..

They were wrong or you described the question incorrectly

It seems you described it implying the engines were not creating thrust and would the mere movement of the backwards runway create vertical lift

That was not the question

The question is clearly asking does the reverse action of the moving runway counter act the forward thrust from the engines and prevent forward motion and lift

The answer is of course it does not and the plane moves forward bye takes off

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By *ralbisw OP Man over a year ago

Exeter

"It is not even complicated.

No movement of air across the wings means no lift.

End of story.

Oh Christ not another one ffs, so what is the prop doing then!?"

Provides thrust

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By *ensualtouch15Man over a year ago

ashby de la zouch

"I don't think anyone is claiming that if the plane is stationary it can take off. I think everyone agrees that the plane needs airflow over the wings.

(Trying to find some common ground!)

The area to focus on is will the plane move forward?

Clearly if there is an equal and opposite force to the engines which pushes the plane backwards, it won't move.

However the moving band doesn't give that. It only spins the wheels (fast!)

The plane doesn't get pushed along by its wheels. They are free spinning. Therefore there is no opposite force to the engines. The plane will move and take off.

The wheels under an aircraft are not by any means free-spinning. There is no way that you could spin just one wheel of even a light aircraft, let alone all of them, or the wheels of a jumbo jet!

Yet again: when the belt starts moving, what pushes the aircraft in the OPPOSITE DIRECTION at the same speed if the engine is off? Please, please, please, tell us!

That's rubbish xxx

Have you not seen an aircraft engine overcome the rolling. Resistance of the wheels , like every time they take off ? Or are manoeuvring around the airport

The op question even tells us the plane is moving

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By *enard ArgenteMan over a year ago

London and France

"I don't think anyone is claiming that if the plane is stationary it can take off. I think everyone agrees that the plane needs airflow over the wings.

(Trying to find some common ground!)

The area to focus on is will the plane move forward?

Clearly if there is an equal and opposite force to the engines which pushes the plane backwards, it won't move.

However the moving band doesn't give that. It only spins the wheels (fast!)

The plane doesn't get pushed along by its wheels. They are free spinning. Therefore there is no opposite force to the engines. The plane will move and take off.

The wheels under an aircraft are not by any means free-spinning. There is no way that you could spin just one wheel of even a light aircraft, let alone all of them, or the wheels of a jumbo jet!

Yet again: when the belt starts moving, what pushes the aircraft in the OPPOSITE DIRECTION at the same speed if the engine is off? Please, please, please, tell us!

You have been fooled by the ( deliberate ) ambiguity of the question; so are answering a question that is not there. And you are examining wheels, when they are irrelevant, and not even in the question.

By the way, the " wheels on paper " you explain is incorrect, because you are saying the object doesn't move on the paper. Misinterpretation; it isn't moving relative to the paper; it is moving relative to everything else and it isn't gravity that is moving it; it's the force of the hand moving the paper that is moving it; due to the friction between the wheels/ paper and bearings, the paper and the wheeled object are one item. Gravity only enables the friction to have an effect as it keeps the object touching the paper. If the inertia of the vehicle overcomes the friction, then the paper and the wheeled object will start to move at different speeds.

It's the same phenomenon as the " whipping tablecloth out from under place settings" pulling the cloth slowly, the force due to friction overcomes the inertia of the cutlery; doing it quickly, the inertia overcomes the force due to friction ( coulomb component of friction in this case)

None of the above, however, have any bearing at all on this aircraft and it's conveyor belt. Apart from that it's not gravity, it's friction, and due to the magnitude difference between friction and thrust, for the purposes of this thought experiment, friction is assumed to be zero, and have no effect on the system.

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By *unandbuckCouple over a year ago

Sheffield

EVERYBODY PAUSE !! THIS IS NOT A PHYSICS PROBLEM !!

Please read this, I'm not trying to prove any point, only to get us to take a step back for a moment.

First , thanks to dee-viant for posting a link yesterday that would have helped all of us.

Things to know:

1 This question is banned on lots of engineering, physics and uni forums.

2 It is NOT a physics question.

3 It is a word /logic puzzle.

4 It is written using 'slight of hand'

5 It is intended to deceive.

99% of people read the question, and come up with an answer. They are then gobsmacked at the 'stupidity' of the other people for getting the answer 'wrong' .

We all then post massive answers explaining physics, lift, airflow, force etc etc.

I did the same and have personally put about 10 posts on here - I'm not Mr know-it-all, I've been sucked in too.

So, empty your mind of Physics and slowly read this word logic puzzle.

Here is the question, exactly as it was originally posted.

So, forgetting any physics, it says the belt copies the speed of the plane, but in the opposite direction.

So for the belt to have any speed the plane has to have speed. Belt at 0mph means plane at 0mph. Belt at 100mph means plane at 100mph.

The explanations we've all been giving are pointless. I include mine in that too. It is just a word logic puzzle.

This puzzle only teaches us that we see something, come to a conclusion and stick to it stubbornly.

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By *rightonsteveMan over a year ago

Brighton - even Hove!

.......so would it take off?

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By *unandbuckCouple over a year ago

Sheffield

[Removed by poster at 19/11/16 10:47:45]

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By *unandbuckCouple over a year ago

Sheffield

".......so would it take off? "

Yes, but only because the puzzle says the plane can move. Can move = can take off.

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By *ensualtouch15Man over a year ago

ashby de la zouch

"EVERYBODY PAUSE !! THIS IS NOT A PHYSICS PROBLEM !!

Please read this, I'm not trying to prove any point, only to get us to take a step back for a moment.

First , thanks to dee-viant for posting a link yesterday that would have helped all of us.

Things to know:

1 This question is banned on lots of engineering, physics and uni forums.

2 It is NOT a physics question.

3 It is a word /logic puzzle.

4 It is written using 'slight of hand'

5 It is intended to deceive.

99% of people read the question, and come up with an answer. They are then gobsmacked at the 'stupidity' of the other people for getting the answer 'wrong' .

We all then post massive answers explaining physics, lift, airflow, force etc etc.

I did the same and have personally put about 10 posts on here - I'm not Mr know-it-all, I've been sucked in too.

So, empty your mind of Physics and slowly read this word logic puzzle.

Here is the question, exactly as it was originally posted.

So, forgetting any physics, it says the belt copies the speed of the plane, but in the opposite direction.

So for the belt to have any speed the plane has to have speed. Belt at 0mph means plane at 0mph. Belt at 100mph means plane at 100mph.

The explanations we've all been giving are pointless. I include mine in that too. It is just a word logic puzzle.

This puzzle only teaches us that we see something, come to a conclusion and stick to it stubbornly.

Exactly pointed out very early on the question gives the answer

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By *ait88Man over a year ago

Plymouth

" That's rubbish xxx

Have you not seen an aircraft engine overcome the rolling. Resistance of the wheels , like every time they take off ? Or are manoeuvring around the airport

The op question even tells us the plane is moving

The engine does indeed move the aircraft along the belt, which is moving it backwards at the same speed. If we were watching, the aircraft would be stationery. Its backwards motion caused by the belt moving is cancelled by the forward motion caused by the engine's thrust.

Also, friction is not a force. If you stand on ice in leather shoes, there is very little friction. But you don't fly off into space. Friction opposes movement, it does not cause it. What can move the aircraft along the belt if the engine os off? Not friction!

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By *ee VianteWoman over a year ago

Somewhere in North Norfolk

Oh for goodness sake

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By *unandbuckCouple over a year ago

Sheffield

" That's rubbish xxx

Have you not seen an aircraft engine overcome the rolling. Resistance of the wheels , like every time they take off ? Or are manoeuvring around the airport

The op question even tells us the plane is moving

STOP THE PHYSICS!

this is a word puzzle and trick!

Look a few posts up then post

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By *ommenhimCouple over a year ago

wigan

"If you're taking it extremes...

How fast will the treadmill need to go for the wheels to generate sufficient wind to cause the plane to lift?

I read that the treadmill goes at the same speed as the wheels, but in opposite directions?

Depending on circumstances - yes. Ground effect."

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By *nequeenslutWoman over a year ago

rugeley

"Original post, just for clarification

yes the plane takes off

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By *ralbisw OP Man over a year ago

Exeter

I think you are right!!

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By *ait88Man over a year ago

Plymouth

STOP THE PHYSICS!

this is a word puzzle and trick!

NO!

We do not take orders from you!

If we wish to answer a question on a Forum we shall do so, regardless of whether it is called a "science" question, a "word puzzle", a "logic" question, or a "trick", or anything else.

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By *inky-MinxWoman over a year ago

Grantham

"I think by now everybody except one or two knows the plane will fly.

More than that, I say it won't and I asked my Dad

What? I thought you were a 'it will move and fly' ?"

Of course not

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By *inky-MinxWoman over a year ago

Grantham

"And still nobody has read the XKCD blog post

The what now?

I mentioned it a couple of times on thread 2.

I can't post a link but it's called "The Goddamn Airplane on the Goddamn Treadmill" and is a blog post on XKCD. It'll be simple enough to find.

But those threads are longer than ours!

Not a thread, a blog post. It's not that long."

I think we prefer to argue it out

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By *ee VianteWoman over a year ago

Somewhere in North Norfolk

STOP THE PHYSICS!

this is a word puzzle and trick!

NO!

We do not take orders from you!

If we wish to answer a question on a Forum we shall do so, regardless of whether it is called a "science" question, a "word puzzle", a "logic" question, or a "trick", or anything else."

Oh dear...

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By (user no longer on site) over a year ago

Bump

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By *ee VianteWoman over a year ago

Somewhere in North Norfolk

"Bump

You are very naughty! Go and stand in the corner and think about what you've done!

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By (user no longer on site) over a year ago

"Bump

You are very naughty! Go and stand in the corner and think about what you've done!

I've been thinking about venturing to the politics forum

Then I thought better of it....much better to get this fire burning again than argue the toss down there

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By *unandbuckCouple over a year ago

Sheffield

" That's rubbish xxx

Have you not seen an aircraft engine overcome the rolling. Resistance of the wheels , like every time they take off ? Or are manoeuvring around the airport

The op question even tells us the plane is moving

Ok, thanks for the post

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By *icolerobbieCouple over a year ago

walsall

"Original post, just for clarification

yes the plane takes off "

Course it cant take off planes dont have wings, you could take 1/4" off the bottom of your new door with it though to stop it gagging on your carpet

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By *ait88Man over a year ago

Plymouth

Come on! We can’t let this one die yet. There are still people who don’t understand why the aircraft can’t take off.

The problem of explaining the reasons why the aircraft doesn’t take of is to finding convincing real-life examples of the principles involved.

There are two Youtube vids that purport to show an actual aircraft on an actual conveyor belt. I’ll take them in turn:

One vid is at: https://www.youtube.com/watch?v=4owlyCOzDiE. The demonstrator has a very small model aircraft on a man-sized treadmill. He demonstrates very clearly that there is a threshold speed at which the model plane’s tiny wheels lose their grip on the treadmill’s surface. At speeds below the threshold, the treadmill’s speed influences the model plane’s speed – he can match them exactly as required by The Question. He shows the model moving backwards and forwards on the treadmill in response to changing throttle settings. At speeds above the threshold, the treadmill speed has no influence on the model’s speed – its tiny wheels are just skidding over the surface. He shows the model maintaining a constant position as he varies the treadmill’s speed. He says: “Once the plane’s speed overcomes the rolling friction of the wheel bearings, the treadmill speed has no influence on the plane”. This is not true. It has nothing to do with “the rolling friction of the wheel bearings”, whatever this quasi-scientific gibberish is supposed to mean. The friction between the surfaces of the treadmill and tiny model wheels has been lost. The wheels are slipping, sliding, skidding, because their tyre surfaces have lost their grip on the treadmill surface. Our diligent investigator offers no reasons for this, no suggestions for scaling the model up to full size along with the treadmill surface and their speeds, and no explanation about how it relevant to The Question. I would guess that the vibrations of the treadmill surface would have a significant effect on the tiny model wheels at a comparatively low speed. Likewise, tiny bumps that would be insignificant to normal aircraft tyres. Our full-sized aircraft is on a full-sized runway, and when it starts to move, the wheels go round. No argument. The problem to solve is: Do the tyres reach their threshold speed (completely lose their grip on the tarmac) before take off speed? Answer: No! Why? Read-on, MacDuff!

The other vid is at: https://m.youtube.com/watch?v=0ul_5DtMLhc. This is the infamous “Mythbuster” vid, and it’s hilarious! It is just “entertainment”, and poor entertainment at that. If features some Good Ole Boys and their Chevvy at the levy, after they’d done a fair bit of drinking whisky and rye!. They do have a light aircraft, sure enough. But their idea of a conveyor belt is a very long cloth towed behind their Chevvy!. Have you every seen a cloth conveyor belt! Why not? Clue; one Good Ole Boy ran a long it, which tore huge holes in it. The damn thing flapped in the breeze! So, ready, steady, go! Watch the background. The aircraft rolls along the “conveyor” like it isn’t there, right from the start. This is in complete contrast to the model experiment. Why? Because, as far as the aircraft is concerned, the “conveyor belt” REALLY isn’t there! The aircraft’s weight forces the weave into the runway surface, and that friction turns the wheels. The cloth just stretches under the weight. Conveyor belts are very rigid. They do not conform to the rollers underneath that support them. But the cloth will conform to the runway surface irregularities under the weight of the aircraft and its wheels. The Question says that the conveyor and aircraft move at exactly the same speeds in opposite directions. The Good Ole Boys don’t show the speeds of either. What actually happened? The pilot firewalled the throttle, sat back, and steered the aircraft. It probably took off at somewhere between 60 and 80 mph. So what about the Good Ole Boy in his cloth-towing Chevvy? How did he match his acceleration with the aircraft’s. Ever seen a Chevvy that can do 0 to 60 IN FIRST GEAR? The best auto-box in the world loses acceleration during shifts. Perhaps their aero engine needed to change gear, too.

The same vid has an insert of a red model aircraft taking off from what we are supposed to think is a conveyor belt. But we are not shown what the belt is made of, how it is moved, or what speeds it and the aircraft are doing at any point in this pointless demo.

A major point of confusion is what happens to the aircraft’s wheels. Are they held tightly down on the conveyor by gravity and friction? Or are they free-spinning because they are not being directly driven round and round – the aircraft is being moved by engine thrust.

My car is rear-wheel driven. The front wheels are not directly driven round and round, they are responding to the engine’s thrust via the rear wheels. They weight of my car makes sure that the front wheels go round and round at the same speed as the rear ones, and enable me to steer around bends. This is true for the whole speed range from 0 to 100 mph.

The wheels on the aircraft in The Question, and in the first part of the model demo, are rotating on the conveyor at a speed which is commensurate with the aircraft’s throttle setting. Therefore when the conveyor moves at the same speed in the opposite direction, the aircraft stays stationary in respect to the ground and ambient air. The wings are not experiencing an airflow. They can not generate life. The aircraft stays put!

Or where have I gone wrong? Exactly.

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By *iamondjoeMan over a year ago

Glastonbury

Still discussing this shit?

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By *iamondjoeMan over a year ago

Glastonbury

The answer is:

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By *iamondjoeMan over a year ago

Glastonbury

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By *enard ArgenteMan over a year ago

London and France

"Come on! We can’t let this one die yet. There are still people who don’t understand why the aircraft can’t take off.

The problem of explaining the reasons why the aircraft doesn’t take of is to finding convincing real-life examples of the principles involved.

There are two Youtube vids that purport to show an actual aircraft on an actual conveyor belt. I’ll take them in turn:

Or where have I gone wrong? Exactly.

Where you have gone wrong is that you are trying to give a physics/ science answer, to a question which is one of logic; and is framed ( deliberately) so that the question can be interpreted in at least 3 ways;

interpretation 1: the aircraft cannot take off as it never moves forward relative to the air

Interpretation 2. The aircraft will always take off because it always moves forward relative to the air

Interpretation 3. The question is framed such that it is an illogical question that can't have an answer, as it is self- contradictory.

All 3 interpretations could be correct.

Thus depending on how you interpret the question;

Th answer that it does take off, and the answer that it doesn't are both valid answers.

What is amusing is seeing people who have taken an interpretation that has an answer that it can take off, proving to themselves that it can't; and vice versa.

And the exposure that a worryingly high number of people have absolutely no idea how a plane flies

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By *ee VianteWoman over a year ago

Somewhere in North Norfolk

"Come on! We can’t let this one die yet. There are still people who don’t understand why the aircraft can’t take off."

Oh do give it a rest.

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By *ait88Man over a year ago

Plymouth

OK. Here is the question again:

I have answered the question – “No”. I will not dispute your definition of what type of question it is, and have given the type of answer that suits my kind of mind. Exactly why can there be no “Logical” answer please? I can see that it would be clearer if the question said “..... The plane THEN moves in one ....”. There is nothing to indicate that the plane moves in any other direction than “forwards”.

Perhaps the question could be more precisely framed:

“A plane moves forward on a runway, which is a large conveyer that moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?”

The question is “Can the plane take off”. It is very specific. The answer can only be “Yes”, “No”, or “Maybe”.

You are aware that there are two Youtube vids about this. It seems that very few people find the question in any way ambiguous. Most people believed they had sufficient understanding to post an answer. Hopefully, a few of them learned something from all of the other answers.

From your observations about the people who posted answers, I would guess that you are quite young. As you get older, you will realise that our hugely expensive education system is an almost complete waste of money for the majority of the children who are forced to submit to it. Most people don’t want to learn. They just want to be entertained. Always have. Always will.

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By *ait88Man over a year ago

Plymouth

Oh do give it a rest."

No!

Stop looking!!!

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By (user no longer on site) over a year ago

I've long since stopped caring about the answer. I'll just make sure there are no conveyor belts at the airports I choose to fly from

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By *ee VianteWoman over a year ago

Somewhere in North Norfolk

Oh do give it a rest.

No!

Stop looking!!!"

Stop bumping it up to the bloody top. It's been done to death.

Are you really this invested in everyone agreeing you are right about whether a hypothetical aircraft takes off? You need a hobby.

It's been explained there are different interpretations of the question possible and different answers as a result. I, myself, have posted info on two articles that explain in detail why there is so much argument over this and how there isn't one right answer.

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By *oo hotCouple over a year ago

North West

"And oh yes! An aircraft parked out of doors with its brakes on and wheels chocked can take off if a wind is blowing directly from ahead at a speed which is greater that its take-off speed. But it will need a damned good pilot!"

A party piece of mine once was to fly "backwards" at 2,000' above the airfield.

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By *oo hotCouple over a year ago

North West

"It is not even complicated.

No movement of air across the wings means no lift.

End of story.

Oh Christ not another one ffs, so what is the prop doing then!?"

A propellor (or a jet engine) provides thrust to propel the whole aircraft forwards and the movement of air across the wings causes lift.

It is not by chance that airport runways are aligned in certain directions and that aircraft take off and land in different directions according to wind speed.

Lets say an aircraft needs an air speed of 100 knots to become airborne. If the wind is 25 knots on the nose, the aircraft only needs to reach 75 knots ground speed to become airborne. Less fuel used, less runway used = more efficient. If the aircraft took off with 25 knot tailwind it would have to achieve 125 knots ground speed before becoming airborne. More fuel used, more runway used and generally less safe and more ineffecient.

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By *ohnaronMan over a year ago

london

Will the rain affect things?

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By *inky-MinxWoman over a year ago

Grantham

"NO"

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By *ohnaronMan over a year ago

london

But aerodynamics is a branch of fluid mechanics.

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By *ralbisw OP Man over a year ago

Exeter

Bump

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By *erbyDalesCplCouple over a year ago

Derbyshire

" Bump"

Turbulence?

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By *enard ArgenteMan over a year ago

London and France

"Will the rain affect things?"

Not the rain as such;

But if it's raining, atmospheric pressure is lower, do air density is lower; you need more velocity to generate lift.

So you need a longer runway and more ground speed to generate the necessary lift.

And if you are in a propeller driven aircraft, the propellor is less efficient in lower pressure air.

That's

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By *unandbuckCouple over a year ago

Sheffield

Correct, this is excatly the reason for not having underwater aeroplanes.

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By *oo hotCouple over a year ago

North West

"Correct, this is excatly the reason for not having underwater aeroplanes."

Except that all submersible water craft manoeuvre underwater using fins that operate in the water on the same principle that a wing operates in the air.

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By *enard ArgenteMan over a year ago

London and France

"Correct, this is excatly the reason for not having underwater aeroplanes.

Except that all submersible water craft manoeuvre underwater using fins that operate in the water on the same principle that a wing operates in the air."

Or hydrofoils

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By (user no longer on site) over a year ago

Bump

Sorry but not sorry

Please think of me when voting for twat of the year award

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By (user no longer on site) over a year ago

"As has been explained countless times....what the conveyor belt is doing is irrelevant

The conveyor belt is keeping the plane stationary relative to the air. So no upthrust.

I put the problem to my eight year old nephew the other week. He was disgusted that he had been asked such a simple problem....especially as his uncle Chris (that's me) has a physics degree.

The thread should have been closed after the second post of thread one.....but let's keep it going to wind up the folks who think the plane might suddenly levitate by narnian magic...

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By *ralbisw OP Man over a year ago

Exeter

Lol..... some bump for a Christmas Eve!

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By *unandbuckCouple over a year ago

Sheffield

"As has been explained countless times....what the conveyor belt is doing is irrelevant

The conveyor belt is keeping the plane stationary relative to the air. So no upthrust.

I put the problem to my eight year old nephew the other week. He was disgusted that he had been asked such a simple problem....especially as his uncle Chris (that's me) has a physics degree.

The thread should have been closed after the second post of thread one.....but let's keep it going to wind up the folks who think the plane might suddenly levitate by narnian magic..."

Nobody thinks the plane will do a vertical take off!

Read thread 1 post 1 very carefully, you'll see why. But I'm not posting an explanation. The answers are in threads 1, 2 and 3.

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By *ralbisw OP Man over a year ago

Exeter

And as it's Christmas .....

I think it will take off. Need a long treadmill though!!

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By *horltzMan over a year ago

heysham

I think this is the one time when I would be happy to see a terrorist blow up a plane

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By *ohnaronMan over a year ago

london

"Will the rain affect things?

Not the rain as such;

But if it's raining, atmospheric pressure is lower, do air density is lower; you need more velocity to generate lift.

So you need a longer runway and more ground speed to generate the necessary lift.

And if you are in a propeller driven aircraft, the propellor is less efficient in lower pressure air.

That's"

You need a fluid mechanic.

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By *eliz NelsonMan over a year ago

The Tantric Tea Shop

What if it was pulled by a red nosed rheindeer?

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By (user no longer on site) over a year ago

I know bugger all about physics and air speed/lift etc but science geeks turn me on. So, I'm hanging around this thread.

I'm going to say no, it won't lift up off the ground. But, if I chuck a paper plane in the air, from a standing position, it flies. So, the plane on the belt, what gives it thrust?

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By (user no longer on site) over a year ago

"What if it was pulled by a red nosed rheindeer?

You would have been drinking too much

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By *obin_and_marionMan over a year ago

Beaconsfield

"Don;t understand why there's even a discussion about it? Title is physics....yet basic physics dictates no forward momentum: no upwards thrust.....not that complicated! "

The plane's forward acceleration is in reaction due to the rearward thrust from the jets, relative to the air, Newtons laws.

So the plane experiences a forward force in reaction to the rearward thrust from the engines.

The friction between the wheels and the conveyor belt determines what happens. Either the tires slip and spin, or they stick.

If they slip then the plane will take off. If they stick then the forward force on the plane and the stuck wheels will force the plane to tip over.

(BTW this explanation from a Cambridge Physics MPhys).

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By *unandbuckCouple over a year ago

Sheffield

The belt can spin at a million miles an hour if it wants to. The engines just exert thrust against the air and the plane moves forward exactly as normal. The wheels are free spinning and just free wheel as fast as the conveyor belt turns them.

The plane moves forward and flies as normal.

Just on this night they can catch up to Santa.

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By *ralbisw OP Man over a year ago

Exeter

This /\/\/\

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By *ait88Man over a year ago

Plymouth

"The belt can spin at a million miles an hour if it wants to. The engines just exert thrust against the air and the plane moves forward exactly as normal. The wheels are free spinning and just free wheel as fast as the conveyor belt turns them.

The plane moves forward and flies as normal.

The wheels are forced down onto the conveyor by gravity, just like the wheels on your car are forced down on the road. The aircraft will move forward in relation to a fixed point on the CONVEYOR. But the conveyor is moving backwards at the same speed, so the aircraft is stationary in relation to a fixed point on the GROUND, and the air surrounding it. There is no “wind” around the wings, so they generate no lift. The aircraft can’t take off.

If you jump onto a treadmill and stand still, it will move you in the same direct as it does, at the same speed, and throw you off. If you “turn on your engine” and walk on the treadmill against its direction of motion and at the same speed, you will be stationery in relation to the gym. If you hold up a hang glider, you will not take off because it can’t “feel” any wind.

The whole thing is hard to get your head around if you don’t have a logical-type mind. References to wheel bearings and daft Youtube vids don’t help!

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By *ohnaronMan over a year ago

london

A watch placed near to the moving belt will run slightly slower due to the gravitational tow indicating the deformation of space/time relative to the aircraft which will now be very slightly father away and thus may be considered to have lifted. Nothing more remains to be said.

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By *unandbuckCouple over a year ago

Sheffield

The plane moves forward and flies as normal.

The whole thing is hard to get your head around if you don’t have a logical-type mind. References to wheel bearings and daft Youtube vids don’t help!

That's true for a car, driven by its wheels, and for you driven by your feet. The aircraft is driven by its engines pushing the air. Its wheels are free spinning on its axles.

If you went on a treadmill at the gym wearing roller skates, and held a rope that's tied to the wall, as the treadmill span, you would stay still and then move forwards as you pulled the rope. The plane would do the same thing. So it could move forward relative to the stationary ground and air around it and would fly.

ps what you are saying and what I'm am saying have been said 175 times in parts 1,2 and 3

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By *ait88Man over a year ago

Plymouth

That's true for a car, driven by its wheels, and for you driven by your feet. The aircraft is driven by its engines pushing the air. Its wheels are free spinning on its axles.

Great. You are on your roller skates on the treadmill. The rope which allows you to stay still in relation to the gym is the aircraft’s engine running at a speed that keeps the skate’s wheels running at exactly the same speed as the treadmill’s, but in the opposite direction. Your “thrust” is the effort you exert holding the rope steady. If you let go (kill the thrust), you move backwards and fall off the end. If you exert greater thrust by pulling on the rope, you move forwards in respect of the gym, and your wheels move at a higher speed than the treadmill speed. This isn’t allowed. The aircraft speed must be equal and opposite to the conveyor speed, and it can only take off if the wheels lose their grip on it. Remember the wheels are held down on the belt by gravity, just like ALL of your car’s wheels (driven or not) are held down on the road, and the skate’s wheels on the treadmill. Try to think about “forces” – effort needed to move.

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By *ait88Man over a year ago

Plymouth

When a plane reaches take-off speed along a runway at say, 150mph, all of the wheels are going round at a speed commensurate with that speed. Abera-cadabera! I wave my magic wand, and the runway instantly becomes a conveyor belt moving at the same speed as the wheels, which is 150mpoh, but in the opposite direct. The aircraft is moving at 150mph along the moving conveyor, but looks stationery to someone in Departures”. No wind around the wings. No flying.

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By *unandbuckCouple over a year ago

Sheffield

Here is a section of the original question:

"This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction)"

So for the belt to have speed the plane has to have speed.

If the plane has speed, it flies.

Remember this is set up as a word puzzle to confuse, and cause argument/discussion.

The question is banned on lots of Physics and University forums.

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By (user no longer on site) over a year ago

The plane is moved forward by its engines not it's wheels, the thrust of the engines will move the plane forward how ever quick the treadmill is moving

Let's say the plane is moving forward at 100 miles an hour, and the convey belt is moving at 100 miles an hour the other way, the plane will move forward at 100 miles an hour, but the wheels will be doing 200 miles an hour, and not affecting the planes forward momentum

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By *unandbuckCouple over a year ago

Sheffield

"The plane is moved forward by its engines not it's wheels, the thrust of the engines will move the plane forward how ever quick the treadmill is moving

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By *errysMan over a year ago

milton keynes and kent

Is this plane a new invention where the wheels drive it along to take off. No it won't take off, also without this conveyor belt if it took off it wouldn't have any drive to keep it going.

if it's powered by prop or jet yes it will.

If it's a jump jet then.......

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By (user no longer on site) over a year ago

with a very basic knowledge of physics and a banging hangover,doesnt Newtons law explain this? force has equal and opposite reaction. jet engines apply thrust against air pressure therefore the wheels are just supporting the plane from crashing to the floor. just a thought but when is a jet ever going to be on a conveyor belt?

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By *ait88Man over a year ago

Plymouth

"Here is a section of the original question:

"This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction)"

So for the belt to have speed the plane has to have speed.

If the plane has speed, it flies."

1. Let’s say that the aircraft’s speed along the runway is 150mph.

A. From the point of view of the runway, the aircraft is moving forward at 150mph.

B. From the point of view of the departure lounge (and the air), the aircraft is moving forward at 150mph.

C. From the point of view of the departure lounge (and the air), the runway is stationary.

D. From the point of view of the aircraft, the runway is moving backwards at 150mph.

E. From the point of view of the aircraft, the departure lounge (and the air) is moving backwards at 150mph.

2. Now move the runway, aka conveyor, backwards at 150mph. The thrust from the aircraft’s engine is unchanged. Whether it is driven by a jet, rocket, piston engine, or drive to one or more wheels like a car, is irrelevant. The wheel revolutions have to be unchanged because they are held down on the runway/conveyor by gravity. The aircraft isn’t flying, i.e. supported by lift generated by the wings. It is supported by the wheels, which are being forced down onto the tarmac by the aircraft’s weight. Just like your car’s wheels at all speeds, whether or not they are the driving wheel

A. From a fixed point on the runway/conveyor, the aircraft is moving forwards at 300mph.

B. From the point of view of the departure lounge (and the air), the aircraft is stationary.

C. From the point of view of the departure lounge (and the air), the runway is moving backwards at 150mph.

D. From the point of view of the aircraft, a fixed point on the runway/conveyor is moving backwards at 300mph.

E. From the point of view of the aircraft, the departure lounge (and the air) is stationary. No airflow around the wings. No lift. No fly.

English is the best language in the world for expressing our thoughts, but when it comes to science and logic, maths is the only way to go. If we were both mathematicians, we wouldn’t be arguing!

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By *inky-MinxWoman over a year ago

Grantham

I can't believe some people still think a stationary plane will fly

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By *unandbuckCouple over a year ago

Sheffield

E. From the point of view of the aircraft, the departure lounge (and the air) is stationary. No airflow around the wings. No lift. No fly.

English is the best language in the world for expressing our thoughts, but when it comes to science and logic, maths is the only way to go. If we were both mathematicians, we wouldn’t be arguing!

My maths is just at the level needed for my electronic engineering degree.

Relative to the lounge, the belt moves backwards at 150mph, the plane moves forward at 150mph, the wheels spin at equivalent of 300mph.

A belt cannot hold back anything with free spinning wheels.

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By *unandbuckCouple over a year ago

Sheffield

"I can't believe some people still think a stationary plane will fly

Nobody does! People who say the plane flies say that because they say the plane moves forward.

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By *ralbisw OP Man over a year ago

Exeter

Roller skates is the best analogy so far I think!

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By *ait88Man over a year ago

Plymouth

Relative to the lounge, the belt moves backwards at 150mph, the plane moves forward at 150mph, the wheels spin at equivalent of 300mph.

A belt cannot hold back anything with free spinning wheels."

Ok.

I agree that, relative to the lounge:

The belt moves backwards at 150mph.

The wheels spin at the equivalent of 300mph.

I disagree that the aircraft is seen to be moving forward at 150mph. What would it be seen to do if the belt was stopped, i.e. a became a normal runway?

I wish I could do a vector analysis!

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By (user no longer on site) over a year ago

[Removed by poster at 27/12/16 08:15:17]

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By (user no longer on site) over a year ago

Relative to the lounge, the belt moves backwards at 150mph, the plane moves forward at 150mph, the wheels spin at equivalent of 300mph.

A belt cannot hold back anything with free spinning wheels.

Ok.

I agree that, relative to the lounge:

The belt moves backwards at 150mph.

The wheels spin at the equivalent of 300mph.

I disagree that the aircraft is seen to be moving forward at 150mph. What would it be seen to do if the belt was stopped, i.e. a became a normal runway?

I wish I could do a vector analysis!

If the belt stopped the plane would still move forward at 150 miles an hour,

The plane will have a airspeed of 150 not matter what is happening underneath,

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By (user no longer on site) over a year ago

"I can't believe some people still think a stationary plane will fly

You are correct a stationary plane cannot fly, but the plane is not stationery it is moved forward by the thrust of the engines the wheels are irrelevant on how the plane moves forward, the are free spinning objects, the only affect the conveyer has is too make the wheels spin quicker"

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By *aGaGagging for itCouple over a year ago

Newcastle upon Tyne

Principle: Airflow over the wings is required to generate lift. Without it the plane will not fly.

Clarification: Although not stated, the plane scenario assumes there to be no head wind. If there was a sufficient head wind the plane could take off without any forward movement.

Now transpose the plane scenario to running on a treadmill. The treamill is spinning at 12 mph, and you are running at 12 mph. Do you feel a 12mph wind on your face? - No, because you have no forward movement. Therefore, no airflow, no lift.

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By (user no longer on site) over a year ago

"Principle: Airflow over the wings is required to generate lift. Without it the plane will not fly.

Clarification: Although not stated, the plane scenario assumes there to be no head wind. If there was a sufficient head wind the plane could take off without any forward movement.

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By (user no longer on site) over a year ago

"Principle: Airflow over the wings is required to generate lift. Without it the plane will not fly.

Clarification: Although not stated, the plane scenario assumes there to be no head wind. If there was a sufficient head wind the plane could take off without any forward movement.

You don't feel any wind because you are not moving, your legs are powering you, the wheels of the plane do not drive the plane, there for the plane will have forward movementthus having airflow and able to take off,

Let's see a treadmill is moving at 12mph and you have a toy plane on the treadmill if you apply force to the toy plane with your hand the plane will not move, if you then push the toy plane up the treadmill the plane will move forward under the thrust of your pushing no matter how fast the treadmill is going??

Using that scenario, the thrust of the planes engine is equivalent to the thrust of your hand on the plane, it is a outward force subjected to. If plane independent to any drive on the wheels thus propelling the plane forward however fast the treadmill is travelling

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By (user no longer on site) over a year ago

Quick question for those who don't think the plane will take off

If the plane is doing 200 mph and the treadmill is doing 400 mph will the plane move backwards at 200 mph?

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By (user no longer on site) over a year ago

"Not read all of the last one but, where is the upwards thrust coming from to lift the wings?

There isn't any because the plane is sitting completely still

Wrong again

In the OP we are told the plane is moving

I am amazed

Seems we need to draw a picture

First level is ground . For this we shall say not moving

Second level is moving surface moving backwards let's say at 100 kph

Third level is a wheel attached to an under carriage and the brakes are off , it can spin freely touching the moving surface . The wheel has a circumference of 1 meter

The undercarriage is tethered to the ground

The wheel is now rotating at 1666 rpm however it's speed relative to the ground is 0 kph

The drag on the undercarriage from the moving surface is about 100 pounds

Attached to the undercarriage is a jet engine that can push at 100 000 pounds

Set the engine to produce 100 pounds thrust

The carriage stays still

Reduce the thrust the undercarriage follows the direction of the moving surface

Increase the thrust to 50 000 pounds and the carriage accelerates forward bringing it's wheels forwards relative to the ground , the moving surface and most importantly the air mass

The only equation that is relevant here is

Acceleration equals mass divided by force

Thus as long as the force on the undercarriage is less than that of the engine the plane accelerates

As wheels are attached to bearings and designed to reduce drag and no where is it suggested the brake would be applied

Gosh simple physics

Yes this

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By (user no longer on site) over a year ago

"Quick question for those who don't think the plane will take off

If the plane is doing 200 mph and the treadmill is doing 400 mph will the plane move backwards at 200 mph?"

Not initially, however the wheel bearings are rotating at 600 mph, so I predict after 30 minutes or so at least one bearing will weld itself into a solid mass and the aircraft will shoot sideways at an uncalculated speed

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By (user no longer on site) over a year ago

"Quick question for those who don't think the plane will take off

If the plane is doing 200 mph and the treadmill is doing 400 mph will the plane move backwards at 200 mph?

I agree at some point the speed will course the wheels to fail and crash, but the plane will be moving forward when that happens

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By (user no longer on site) over a year ago

And........

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By (user no longer on site) over a year ago

Finished....yay!

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