would the plane take off..

[Ali123]

following from mochachino's thread it reminded me of this from another forum!

so as the title says,

would the plane take off if it was on a rolling runway ( runway being as long as any other runway ) , going in the opposite direction to the plane at the same speed

i think the plane would take off since the propulsion of the plane isnt through the wheels, therefore the runway going in the opposite direction wont cancel it out


discuss peoples

[piranhamatt]

something about airflow and thrust would mean it wont?

Unless there was a huge fan blasting air at it fast

[Mochachino]

lol this made me laugh! What goes through peoples minds to think of this.

Well, how does the plane move in the air? But then, who do planes such as the 747 go 180mph before they take off? Or is it just happens to be that mph when the engines develop enough thrust?

[Gareth_R]

no it wouldnt as air wouldnt be moving over the wings. Propulsion isnt the issue, lift is! so what would probably happen is the plane would still shoot forward and if the runway wasnt big enough it would crash

/thread

[Mochachino]

Ahh good point, if the plane is accelerating forward at 100mph but the runway is moving in the oppsite direction at 100mph then it would be a vertical takeoff.

[Gareth_R]

no, if the plane is going at 100 and the runway is going at 100 the other way, the plane will act normally but the wheels will be moving at 200

[Quick]

If its accelerating, then its gaining speed!

As the wheels only freewheel then it would take off!

[Ali123]

lol this made me laugh! What goes through peoples minds to think of this.





ahaha well what made you think of the aqaplaning one ?;)



no, if the plane is going at 100 and the runway is going at 100 the other way, the plane will act normally but the wheels will be moving at 200


i still think it would take off since it will still be moving forwards, therefore generating enough lift to take off

[Ali123]

If its accelerating, then its gaining speed!

As the wheels only freewheel then it would take off!

exactly my point

[Mochachino]

no, if the plane is going at 100 and the runway is going at 100 the other way, the plane will act normally but the wheels will be moving at 200

So actually, to answer the question we need to know what speed the plane is traveling at and also what speed the runway is traveling at in the opposite direction?

If the plane was accelerating at whatever rate it does up to 180mph but the runway was traveling in the opposite direction at 280mph then the engines would have to develop 50% more thrust to create 50% more lift so the plane takes off?

But can the engines produce that much extra? But as we are saying runways moving in the opposite direction we can pretend the engines do :S

[GC_Belfast]

following from mochachino's thread it reminded me of this from another forum!

so as the title says,

would the plane take off if it was on a rolling runway, going in the opposite direction to the plane at the same speed

i think the plane would take off since the propulsion of the plane isnt through the wheels, therefore the runway going in the opposite direction wont cancel it out


discuss peoples

The wheels dont acutally do anything for movement, apart from stopping when they fire the emergency brakes and reverse thrust on. It all comes from the turbines/props pushing the fuselage along. So yes it would still take off.

Mythbusters did an episode on it (wanker alert)

[ed-bradley]

No.

It needs lift..

There would be no airflow over and under the wings to produce any.

Edit: Still having a Mindfuck about this.

[Ali123]

The wheels dont acutally do anything for movement, apart from stopping when they fire the emergency brakes and reverse thrust on. It all comes from the turbines/props pushing the fuselage along. So yes it would still take off.

Mythbusters did an episode on it (wanker alert)


yep exactly and you had to ruin it didnt you, you turd! :clapping: :P

but still interested in seeing peoples opinions

[GC_Belfast]

yep exactly and you had to ruin it didnt you, you turd! :clapping: :P

but still interested in seeing peoples opinions

Well I did call myself a wanker ;)

:D I have the edit button now :D

[JoshFurioBrookes]

So would the plane suddenly shoot forward once it leaves the moving runway?

[Gareth_R]

the speed the runway is travelling at doesnt make a sods worth of difference. My first post was on the assumption that it would be a really small rolling runway, which wouldnt work. The runway would have to be as big as any other runway. The wheels freewheel as mentioned above so the plane would behave exactly as it would on a static runway, and need just as much thrust and lift to take off, plus a little extra to overcome the relatively small additional friction caused by the runway moving

IMO

[Ali123]

the speed the runway is travelling at doesnt make a sods worth of difference. My first post was on the assumption that it would be a really small rolling runway, which wouldnt work. The runway would have to be as big as any other runway. The wheels freewheel as mentioned above so the plane would behave exactly as it would on a static runway, and need just as much thrust and lift to take off, plus a little extra to overcome the relatively small additional friction caused by the runway moving

IMO



should of worded it better! the run way being long enough as any other run way!

shall edit the first post now

[GC_Belfast]

So would the plane suddenly shoot forward once it leaves the moving runway?

Nope, it'll stay at take off speed.

[Mochachino]

I get it now.

Just think, when the plane is in the air, if you put a treadmill under it would it suddenly stop? No it would carry on as its thrusting forward.

[Ali123]

Well I did call myself a wanker ;)

:D I have the edit button now :D

nawwww :hug::hug:

[GC_Belfast]

No.

It needs lift..

There would be no airflow over and under the wings to produce any.

Edit: Still having a Mindfuck about this.

Air is still moving over the wings and as soon as the alierons (sp) are moved to the ascend position the air over the wings will change and it would take off as normal

Just to be an more of an arsehole:

http://www.youtube.com/watch?v=0KsdMuhYJPw

[Ali123]

Air is still moving over the wings and as soon as the alierons (sp) are moved to the ascend position the air over the wings will change and it would take off as normal

Just to be an more of an arsehole:

http://www.youtube.com/watch?v=0KsdMuhYJPw

had to ruin ittttttttttttttttttttttttttttttttttttttttttttt!!!! !!!!!!!!!!!!!!!!!

:(

[GC_Belfast]

had to ruin ittttttttttttttttttttttttttttttttttttttttttttt!!!! !!!!!!!!!!!!!!!!!

:(

Its what I do ;)

[Ali123]

Its what I do ;)

pfffft! gtfo ;)

[ed-bradley]

Air is still moving over the wings and as soon as the alierons (sp) are moved to the ascend position the air over the wings will change and it would take off as normal

Just to be an more of an arsehole:

http://www.youtube.com/watch?v=0KsdMuhYJPw

The plane is moving faster than the belt under it though, so its still going forwards.. May aswell not have it there at all.

How would air be moving over the wings?
If the Runway/rolling road under it was travelling --> at 100mph, and the plane was travelling <-- at 100mph.

Its not moving anywhere in theory, no air would pass over it.
The only thing moving would be the wheels at 200mph.


Think about it.. If you had a hand glider on a tread mill, and ran at 15mph, and the treadmill was set at 15mph.. You wouldn't lift off at all. You'd just look a twat.

[baker556]

The plane is moving faster than the belt under it though, so its still going forwards.. May aswell not have it there at all.

How would air be moving over the wings?
If the Runway/rolling road under it was travelling --> at 100mph, and the plane was travelling <-- at 100mph.

Its not moving anywhere in theory, no air would pass over it.
The only thing moving would be the wheels at 200mph.


Think about it.. If you had a hand glider on a tread mill, and ran at 15mph, and the treadmill was set at 15mph.. You wouldn't lift off at all. You'd just look a twat.

Good angle however planes do not take off with the sole purpose of the wings, its the thrust from the jet engines, that drive the plane forward then the wings create drag to lift.

But without moving forward they cannot just get up and hover.

Surely a plane needs to move forward to lift with the wings, if the conveyer belt kept it still in once place it could not just lift?

Actually thinking about it, it would lift. Hold a model aeroplane still turn the engines on full and it lifts. The same principle would be if the conveyer belt was the same speed as the plane it would be still, when the engines reach speed it will just go.

[baker556]

What it comes down to is it cannot hover however it needs some rolling resistance to get it in motion.

[Rogue_Shadow]

Meh Who cares

This is more epic than a Plane on a treadmill! (http://www.youtube.com/watch?v=711bZ_pLusQ)
Smaller scale ... but has its own soundtrack :y:
Night lol

[Nates-VTR]

I ran on a treadmill with my arms out, I didn't fly.

[Mr_P]

The plane is moving faster than the belt under it though, so its still going forwards.. May aswell not have it there at all.

How would air be moving over the wings?
If the Runway/rolling road under it was travelling --> at 100mph, and the plane was travelling <-- at 100mph.

Its not moving anywhere in theory, no air would pass over it.
The only thing moving would be the wheels at 200mph.


Think about it.. If you had a hand glider on a tread mill, and ran at 15mph, and the treadmill was set at 15mph.. You wouldn't lift off at all. You'd just look a twat.

But the wheels on a plane do not drive it. The jet engines on the wings do. So all they have to do is overcome the additional friction in the wheel bearing. The plane will take off as normal. It doesn't matter if the belt travels at twice the speed of the plane. The wheels would just spin at the combined speed of the belt and the plane.

[devilsadvocate]

Yes it would, a plane takes off using thrust from the engines not the wheels.

Other than keeping it in a straight line when rolling down the runway, the wheels have no part in how a plane takes off.

Once there is enough airflow passing over the wings, the plane will be able to leave the ground.

[GolfJay]

No it wouldn't. If a plane is doing 100mph and the road is doing 100mph in te other direction then it isn't moving. A plane cannot take off without the air flow under the wings (That's the whole reason it has wings) No movement = no airflow.

[MuZiZZle]

what the fuck is wrong with you all?

go and sit in your car, parked up, stick your hand out of the window, with it flat, does it feel like your hand is going to take off? no

now repeat, but at 150mph

FYL!

[tokyodrifte]

....No

[titchster]

Air is still moving over the wings and as soon as the alierons (sp) are moved to the ascend position the air over the wings will change and it would take off as normal

Just to be an more of an arsehole:

http://www.youtube.com/watch?v=0KsdMuhYJPw

Elevators. Ailerons control the roll, elevators control the pitch (up and down). ;)


But yes, the plane would take off. Regardless of how fast the 'runway' is moving, since the wheels would just rotate at whatever speed (for example, if the plane's doing an indicated 100mph, the wheels would be doing 200mph, and so on, the thrust comes from the engines on the wings, rather than the wheels, which have no bearing on aircraft velocity.

[Manu]

So no one yet mentioned why an airplane carrier faces the wind for takeoffs. That's your moving runway philosophy sorted by the way. An airplane can perfectly take off from a standstill if the lift coeficient is superior to the weight of the plane.

http://www.youtube.com/watch?v=cHhZwvdRR5c

http://www.youtube.com/watch?v=nsIzCqAQOck

[MuZiZZle]

So no one yet mentioned why an airplane carrier faces the wind for takeoffs. That's your moving runway philosophy sorted by the way. An airplane can perfectly take off from a standstill if the lift coeficient is superior to the weight of the plane.

http://www.youtube.com/watch?v=cHhZwvdRR5c

http://www.youtube.com/watch?v=nsIzCqAQOck

for that 747 to lift off the ground though, the wind would need to be 210mph+

[blackie_2k5]

Repost

[GolfJay]

what the fuck is wrong with you all?

go and sit in your car, parked up, stick your hand out of the window, with it flat, does it feel like your hand is going to take off? no

now repeat, but at 150mph

FYL!

Exact example I was going to use. It's down to the air going past your arm though. Without moving you wouldn't have that.

[craig180]

In need of face palm.

How stupid are some people?!!!!!!

Of course it wouldn't take off you morons. There are 3 factors. The plane, the surrounding air and the ground. For flight there needs to be the plane travelling through air. Take the air out of the equation and there is no flight.

[Mike_Roberts]

So many people on this thread are just confusing themselves...

There is a massive difference between airspeed and groundspeed which is what some people on here are confused about. Regardless of how fast the runway is moving (groundspeed), if the airspeed is adequate then it will still take off.

It all becomes quite simple after sitting through hours and hours of aerodynamic theory..

[Jungle]

In need of face palm.

How stupid are some people?!!!!!!

Of course it wouldn't take off you morons. There are 3 factors. The plane, the surrounding air and the ground. For flight there needs to be the plane travelling through air. Take the air out of the equation and there is no flight.

Erm...... Please explain where the air has gone? :wacko:

To those that say the plane will not take off because the rolling road will counteract the thrust and it ill just stand still... Your retarded, really really retarded.

To those that say it is not the wheels driving it along so it will make no difference, it's a good theory but I don't think it's that simple. There would be a hell of a lot of resistance to overcome with the weight of a plane and the rolling resistance of the wheels etc.

Conclusion is: I don't know, but if you said that it would have no airflow over the wings you are really really stupid.

[Proffitt]

Surely though, if the plane and the treadmil are accelerating at the exact same speed the plane would stay stationary?

[titchster]

If the wheels are what propelled it, and the 'runway' was moving at the same speed, in the opposite direction, then no, it wouldn't take off. But they aren't. So, all that will happen is that they'll spin twice as fast as normal.

I don't see where the issue with understanding that is?

[devilsadvocate]

The scenario doesnt give enough information, it doesnt state whether the plane is allowed to increase thrust to the engines.

If it is allowed then it would be able to take off.

[Proffitt]

If the wheels are what propelled it, and the 'runway' was moving at the same speed, in the opposite direction, then no, it wouldn't take off. But they aren't. So, all that will happen is that they'll spin twice as fast as normal.

I don't see where the issue with understanding that is?

I know that but surely if the engine was producing the same thurst to travel at the same speed as the rolling runway and the accelerate at the same speed then the plane would stay staionary.
Only when the plane increase thrust higher than the speed of the rolling runway it would then move forward and take off?

[Jungle]

Surely though, if the plane and the treadmil are accelerating at the exact same speed the plane would stay stationary?

Do you understand how a plane works? :wall:

Edit: Seen you next post, it appears not.

A plane does not need road speed to get airborne, it needs lift. Lift is created by air passing over the wings. The wheels are there solely to keep it from smashing into the floor. The fact that the ground is moving will make it a little harder to get up to speed only because of the resistance caused. It will not completely counteract the planes forward acceleration unless they are using the shittiest bearings known to man, we know they are not using shit bearings because when a plane lands the wheels go from being stationary to spinning very fast instantly, and it does not do a front flip.

HAVE I COVERED IT IN ENOUGH DETAIL YET?

[MuZiZZle]

basically you can take the wheels & runway out of the equation, it's the speed of the thrust from the engine against the air that makes the plane move

[titchster]

^That.

[Proffitt]

Do you understand how a plane works? :wall:

See my above comment, i've worded it a bit better.

[titchster]

I'd just like to make a point here. Mythbusters proved that it would.


An airplane cannot take off from a runway which is moving backwards (like a treadmill) at a speed equal to its normal ground speed during takeoff.


BUSTED

First some small-scale tests were performed with a model airplane on a treadmill and the plane was able to take off. For the large-scale test, the MythBusters used a 400 pound ultralight aircraft with a 2000 foot tarp under it. The tarp was pulled backwards to simulate a moving runway. The ultralight pilot had no trouble taking off. This is because the thrust of the airplane engines acts on the air, not on the ground.

http://www.youtube.com/watch?v=0ul_5DtMLhc

Skip to 3 minutes.

[GolfJay]

If the treadmill is going at 100mph and the thrust is at 100mph ONLY (Being the same speed) then it wouldn't take off.

Ignore the fact that a plane uses thrust, it complicates things.

If its a permenant 100mph in opposite directions then it won't take off.

[titchster]

If its a permenant 100mph in opposite directions then it won't take off.


Yes, it will. The plane will go 100mph > way. The 'runway' will go 100mph < way, and the wheels will do 200mph.

[Giraffe]

If the treadmill is going at 100mph and the thrust is at 100mph ONLY (Being the same speed) then it wouldn't take off.

Ignore the fact that a plane uses thrust, it complicates things.

If its a permenant 100mph in opposite directions then it won't take off.

Fucking lol. Why you trolling? Trolling or just too dumb to understand what everyone else has explained?

The wheels DO NOT drive the plane. They provide minimal friction. Imagine you put a toy car on a treadmill going 100mph and the bearings were amazing so the wheels would spin freely. You could put your finger behind it and it wouldn't move. With minimal effort you could push the car forward. That's because the wheels are spinning entirely freely, the only force you have to overcome is the friction of the bearings... Same applies to the plane. The thrust pushes the plane forward and as the only resistant force is air, which it needs anyway, it would take off.

[Era]

http://seemslegit.com/_images/0e70f3e6ba1f537063d2298b2b797563/1750%20-%200featured-image%20fly%20plane%20treadmill%20vehicles.JPG

[Jungle]

If the treadmill is going at 100mph and the thrust is at 100mph ONLY (Being the same speed) then it wouldn't take off.

Ignore the fact that a plane uses thrust, it complicates things.

If its a permenant 100mph in opposite directions then it won't take off.

http://cdn.memegenerator.net/instances/400x/19708860.jpg

[craig180]

Do you understand how a plane works? :wall:

Edit: Seen you next post, it appears not.

A plane does not need road speed to get airborne, it needs lift. Lift is created by air passing over the wings. The wheels are there solely to keep it from smashing into the floor. The fact that the ground is moving will make it a little harder to get up to speed only because of the resistance caused. It will not completely counteract the planes forward acceleration unless they are using the shittiest bearings known to man, we know they are not using shit bearings because when a plane lands the wheels go from being stationary to spinning very fast instantly, and it does not do a front flip.

HAVE I COVERED IT IN ENOUGH DETAIL YET?


I love the fact you've contradicted yourself after calling me a moron.

If the plane is static, relative to the air around it there is no lift, therefore no flight.

Believe me, when it comes to applied mathematics you won't win an argument with me ;)

[Ash1711]

It won't take off if the plane is stationery (which it would be if it was moving forward at 100mph and the runway was moving backwards at 100mph) does everyone agree that the plane would be stationery? Just like you would be if you ran at 10mph on a treadmill set at 10mph - you dont feel wind hitting you in the face and the plane wouldn't have any wind/air under its wings to enable it to lift. I don't care what mythbusters say - they're wrong.

I think there is some confusion about the plane being staionery or not - if the runway was set at 100mph and the plane could provide thrust to the equivalent of 200mph then the plane would be moving forward along the runway and it would have air under the wings and it would take off.

Somebody made a good point before: if it was able to take off while remaining in a stationery position would it just go from 0 - 200mph in less than a second as it lifts off the runway? WOULD IT FUCK!

People are stupid.

[matt_vtr_15a]

It won't take off if the plane is stationery (which it would be if it was moving forward at 100mph and the runway was moving backwards at 100mph) does everyone agree that the plane would be stationery? Just like you would be if you ran at 10mph on a treadmill set at 10mph - you dont feel wind hitting you in the face and the plane wouldn't have any wind/air under its wings to enable it to lift. I don't care what mythbusters say - they're wrong.

I think there is some confusion about the plane being staionery or not - if the runway was set at 100mph and the plane could provide thrust to the equivalent of 200mph then the plane would be moving forward along the runway and it would have air under the wings and it would take off.

Somebody made a good point before: if it was able to take off while remaining in a stationery position would it just go from 0 - 200mph in less than a second as it lifts off the runway? WOULD IT FUCK!

People are stupid.

Hi,

You're wrong

The End

[Giraffe]

The difference is that your legs drive your body, the wheels of a plane do not drive the plane. If you put a block of wood on a treadmill going 100mph, the block of wood would go 100mph in the direction of the treadmill yes? If you put something with free turning wheels on a treadmill at 100mph, the WHEELS move at 100mph, but as they are spinning, the only thing that would move the plane backwards would be the friction generated by the bearings and the contact with the treadmill. You would only need force equal to or greater than the friction to either hold the plane stationery or move it forwards... The force of the treadmill is applied to the WHEELS which spin of their own accord.

Seriously Ash, you're wrong, and even more stupid for trying to claim anyone else is...

[Ash1711]

Dave, if you can answer my questions that'll help me understand that you are right but haven't answered them... how does a plane get itself into the air? By moving fast enough so the pressure of the air underneath the wings lift it into the air yes?

So how do you generate enough air pressure underneath the wings when it actually isn't moving anywhere? (I refer back to my question about running on a treadmill - no wind hits you in the face does it?)

[Ash1711]

Also, i understand that the wheels do not drive the plane its the thrust but if the thrust propels the plane forward at the same rate the the treadmill pulls the plane back - it will be stationery and no air = no flight!

[Giraffe]

Also, i understand that the wheels do not drive the plane its the thrust but if the thrust propels the plane forward at the same rate the the treadmill pulls the plane back - it will be stationery and no air = no flight!

That's the thing, the PLANE isn't being pulled back at the same speed as the treadmill, the wheels are, and the wheels move freely. Tell me this, if you went on a treadmill on some roller skates and held the sides of the treadmill, would the speed the treadmill was going make any difference as to whether you stayed static or not if the bearings to the wheels were good?

http://www.youtube.com/watch?v=BSkzm_qHsDg

Watch, you may understand better.

[matt_vtr_15a]

Also, i understand that the wheels do not drive the plane its the thrust but if the thrust propels the plane forward at the same rate the the treadmill pulls the plane back - it will be stationery and no air = no flight!

how can he answer a question that you keep totally missing the point to...

there is air passing past the wings as the plane is physically moving, it is not stationary....

that is the point you can't understand....

[titchster]

Tell me this, if you went on a treadmill on some roller skates and held the sides of the treadmill, would the speed the treadmill was going make any difference as to whether you stayed static or not if the bearings to the wheels were good?

This theory has just given me an idea.


Imagine, you're on a treadmill, on roller skates, as Dave said, and you're holding onto the sides, you won't go anywhere, right? Now imagine you use your arms to pull yourself forward, just think, regardless of how much force you put in, you're going to move forward. Now imagine, you're a plane, and your arms are the engines...


I know what you guys are saying about will the engines produce enough forward thrust to overcome the 'runway', but they're not actually overcoming the 'runway', the thrust has only got to overcome the friction in the wheel bearings, if it does that, it'll equal the speed of the 'runway' and be stationary/move.

[Ash1711]

I think that's the point that most people misunderstand - I blame the question lol.

If the plane remains stationary - it wouldn't fly - that's what my previous comments were based on.

However, Dave and Matt are arguing that the plane wouldn't remain stationery as the wheels don't propel the plane, they just stop it from touching the floor... in the case that the thrust WOULD push the plane forward I agree that the plane would take off.

Everybody in agreement?

[craig180]

It won't take off if the plane is stationery (which it would be if it was moving forward at 100mph and the runway was moving backwards at 100mph) does everyone agree that the plane would be stationery? Just like you would be if you ran at 10mph on a treadmill set at 10mph - you dont feel wind hitting you in the face and the plane wouldn't have any wind/air under its wings to enable it to lift. I don't care what mythbusters say - they're wrong.

I think there is some confusion about the plane being staionery or not - if the runway was set at 100mph and the plane could provide thrust to the equivalent of 200mph then the plane would be moving forward along the runway and it would have air under the wings and it would take off.

Somebody made a good point before: if it was able to take off while remaining in a stationery position would it just go from 0 - 200mph in less than a second as it lifts off the runway? WOULD IT FUCK!

People are stupid.
You are right

Hi,

You're wrong

The End
You are wrong

The difference is that your legs drive your body, the wheels of a plane do not drive the plane. If you put a block of wood on a treadmill going 100mph, the block of wood would go 100mph in the direction of the treadmill yes? If you put something with free turning wheels on a treadmill at 100mph, the WHEELS move at 100mph, but as they are spinning, the only thing that would move the plane backwards would be the friction generated by the bearings and the contact with the treadmill. You would only need force equal to or greater than the friction to either hold the plane stationery or move it forwards... The force of the treadmill is applied to the WHEELS which spin of their own accord.

Seriously Ash, you're wrong, and even more stupid for trying to claim anyone else is...

You're confused.

[titchster]

Craig, Mythbusters proved it. See post 51. YOU are wrong. ;)

[craig180]

In simpleton terms. If the plane is travelling forward at 100mph and the surface underneath is travelling at 100mph the plane has an actual speed of 0mph through the air around it.

The plane relies on thrust (accelleration in the opposite direction to move forward) AND here's the clincher........... LIFT.

Lift is created by wind passing over and/or under an aeroplane wing.

If the gross speed of the plane is 0mph there is no lift, therefore no flight.,

I am right, those that disagree with me are wrong.

[matt_vtr_15a]

I think that's the point that most people misunderstand - I blame the question lol.

If the plane remains stationary - it wouldn't fly - that's what my previous comments were based on.

However, Dave and Matt are arguing that the plane wouldn't remain stationery as the wheels don't propel the plane, they just stop it from touching the floor... in the case that the thrust WOULD push the plane forward I agree that the plane would take off.

Everybody in agreement?

I agree

You are right


You are wrong



You're confused.

See above comment I think some people get confused about the question ;)

[craig180]

Craig, Mythbusters proved it. See post 51. YOU are wrong. ;)

Look at the video again. The plane has forward momentum creating lift.

IE, the forward speed of the plane was more than (not equal to) the speed of the surface going the opposite direction below it.

If you look at it mathematically, and the original question gives you the answer to this, the forward speed of the plane is 0mph

[Giraffe]

In simpleton terms. If the plane is travelling forward at 100mph and the surface underneath is travelling at 100mph the plane has an actual speed of 0mph through the air around it.

The plane relies on thrush (accelleration in the opposite direction to move forward) AND here's the clincher........... LIFT.

Lift is created by wind passing over and/or under an aeroplane wing.

If the gross speed of the plane is 0mph there is no lift, therefore no flight.,

I am right, those that disagree with me are wrong.

I am confused, but I think you are explaining it terribly...

If the plane was being pulled backward at a speed of 100mph by the moving runway beneath it, and the engines were propelling it forwards to a speed of 100mph, then yes the plane would remain static and not take off.

HOWEVER, if the moving runway were moving at a speed of 100mph, the wheels of the plane would be moving at that speed, but the plane itself would not be moving at that speed, therefore the engines would only need to make the plane move at whatever speed the PLANE was moving backwards... If the PLANE was moving at 100mph forwards, and the treadmill was moving at 100mph, the plane would move forwards....

But yes, I agree that if the plane were to remain static, the plane would not move... and by move I mean fly lol

[baker556]

After all the comments in here i have to a conclusion that everyone is looking at it in the wrong angle.

Don't think as the wheels and what they are doing, they have no gear they just move freely.

Depending on what type of plane we are talking here im thinking something big, Boeing 747 for example.

The engines have so much thrust the bearings in the wheels and treadmill almost become irrelevant. I was thinking if the plane had the brakes on it couldn't just take off and hover. As this is on a treadmill even if it was to match the speed of the thrust of a plane it would still take off.

Think of a rocket on a conveyer belt, eventually it would go to the end. Don't think about matching speed and standing still its irrelevant, its a conveyor belt in which the plane will move forward on eventually.

[craig180]

following from mochachino's thread it reminded me of this from another forum!

so as the title says,

would the plane take off if it was on a rolling runway ( runway being as long as any other runway ) , going in the opposite direction to the plane at the same speedi think the plane would take off since the propulsion of the plane isnt through the wheels, therefore the runway going in the opposite direction wont cancel it out


discuss peoples

It's not rocket surgery.

One is going forward at Xmph, the other the opposite direction at the same Xmph, the gross speed is 0! x-x = 0, regardless of the value of x

I put all the wrong answers in this thread down to people's lack of being able to read a question properly, rather than their lack of math skill.

[Giraffe]

It's not rocket surgery.

One is going forward at Xmph, the other the opposite direction at the same Xmph, the gross speed is 0! x-x = 0, regardless of the value of x

Yes, but if the plane is moving forwards at 100mph, and the treadmill is moving the opposite way at 100mph, the plane will still be moving forwards by virtue of the fact that the force is being applied to two different objects? The treadmill can only make the wheels spin as fast as the treadmill, not the actual plane itself, so the plane would not be moving at the same speed as the treadmill. The treadmill would need to be moving much faster than the plane was moving forwards, surely?

This isn't just about maths either, surely it's physics?

[matt_vtr_15a]

It's not rocket surgery.

One is going forward at Xmph, the other the opposite direction at the same Xmph, the gross speed is 0! x-x = 0, regardless of the value of x

True,, i think the best way to understand is as somebody has explained...


Imagine you're stood on a flat treadmill wearing rollerblades...

If the treadmill was moving at 20mph you would remain static and the wheels would just spin however the person (the plane) would remain in the same position as only the wheels are in motion..

the person then uses their arms (jets) which with ease could pull yourself forwards... in which would in turn take the wheels with it...

Ahhh I just get more headfucked the more I try and explain,


P.S Dave, this is all physics...maths barely comes into it you're correct

[Era]

In simpleton terms. If the plane is travelling forward at 100mph and the surface underneath is travelling at 100mph the plane has an actual speed of 0mph through the air around it.

The plane relies on thrust (accelleration in the opposite direction to move forward) AND here's the clincher........... LIFT.

Lift is created by wind passing over and/or under an aeroplane wing.

If the gross speed of the plane is 0mph there is no lift, therefore no flight.,

I am right, those that disagree with me are wrong.

But, the original question says the conveyor belt only moves backwards if the plane moves forwards. You propose the plane will always remain at 0mph, therefore so will the conveyor belt. In this scenario can you imagine a 747 with all 4 jet engines at full thrust, no brakes on yet the plane is sitting still and so is the conveyor? Impossible.

As said before, the plane travels forwards normally up until ~180mph take off speed, the conveyor moves backwards in increments matching to ~180mph, the wheels spin freely under the plane at ~360mph, the plane takes off as normal.

[craig180]

Yes, but if the plane is moving forwards at 100mph, and the treadmill is moving the opposite way at 100mph, the plane will still be moving forwards by virtue of the fact that the force is being applied to two different objects? The treadmill can only make the wheels spin as fast as the treadmill, not the actual plane itself, so the plane would not be moving at the same speed as the treadmill. The treadmill would need to be moving much faster than the plane was moving forwards, surely?

This isn't just about maths either, surely it's physics?

Physics is 90% maths.

The plane isn't moving forward. For the plane to be moving at all (relative to the air around it and not the treadmill), in either direction the speed of the treadmill would have to be different to the speed of the plane.

(plane) 100mph
(treadmill) -100mph as it's going the opposite direction

Overall speed = 0mph


What the mythbusters vidoe showed was a plane travelling at 0mph relative to the belt, but the same speed as the belt relative to the air, therefore the belt was creating the "thrust" and the air moving over the wings was creating the lift

[matt_vtr_15a]

watch this craig

http://www.youtube.com/watch?v=4owlyCOzDiE

[Giraffe]

But, the original question says the conveyor belt only moves backwards if the plane moves forwards. You propose the plane will always remain at 0mph, therefore so will the conveyor belt. In this scenario can you imagine a 747 with all 4 jet engines at full thrust, no brakes on yet the plane is sitting still and so is the conveyor? Impossible.

As said before, the plane travels forwards normally up until ~180mph take off speed, the conveyor moves backwards in increments matching to ~180mph, the wheels spin freely under the plane at ~360mph, the plane takes off as normal.

I think the question is inferring that the conveyor belt is moving of it's own accord, like a treadmill. So lets say the treadmill is running at 100mph, and the thrusts are set in such a way that the plane would be moving forwards at 100mph, Craig is saying that the speed would equal 0...

I say it would be moving forwards, but not at 100mph, slightly less.

[craig180]

But, the original question says the conveyor belt only moves backwards if the plane moves forwards. You propose the plane will always remain at 0mph, therefore so will the conveyor belt. In this scenario can you imagine a 747 with all 4 jet engines at full thrust, no brakes on yet the plane is sitting still and so is the conveyor? Impossible.

As said before, the plane travels forwards normally up until ~180mph take off speed, the conveyor moves backwards in increments matching to ~180mph, the wheels spin freely under the plane at ~360mph, the plane takes off as normal.

The orioginal question stated the 2 moving the opposite directions AT THE SAME SPEED, therefore there is no difference in speed, therefore no movement of the plane, which will always be going 0mph through the air, regardless of whether it and the conveyer belt are both doing 1090948760746746128640746209mph in the opposite direction.

The speed of each can be anything, but if they are both ALWAYS THE SAME then the overall speed is 0mph

Is it really that difficult to understand??? :err:

[Era]

Turn it on its head.

If a plane came in to land at 180mph before it touched down, and was landing on a conveyor belt going at 180mph in the opposite direction, what would happen?

Would the plane suddenly stop an thus kill everyone on board? Or would the wheels touch down, spin at ~360mph and the plane would slow from its 180mph to a normal stop?

Edit, I am assuming the conveyor moves backwards at the same speed the plane moves forwards, as the original question asks, so that when the plane brakes to a stop, so does the conveyor.

[baker556]

Physics is 90% maths.

The plane isn't moving forward. For the plane to be moving at all (relative to the air around it and not the treadmill), in either direction the speed of the treadmill would have to be different to the speed of the plane.

(plane) 100mph
(treadmill) -100mph as it's going the opposite direction

Overall speed = 0mph


What the mythbusters vidoe showed was a plane travelling at 0mph relative to the belt, but the same speed as the belt relative to the air, therefore the belt was creating the "thrust" and the air moving over the wings was creating the lift

Lets be realistic a big ass treadmill would create a strong headwind at 100mph planes take off better in a head wind. The plane would take off.

Your looking at it all being stationary well its not its on a treadmill.

Wind created from the treadmill would cause the lift, remember this plane is not stationary i understand the 100mph and 100mph = 0 mph what about the headwind?

http://ffden-2.phys.uaf.edu/211_fall2002.web.dir/josh_palmer/berni%20wing.gif

[Giraffe]

Physics is 90% maths.

The plane isn't moving forward. For the plane to be moving at all (relative to the air around it and not the treadmill), in either direction the speed of the treadmill would have to be different to the speed of the plane.

(plane) 100mph
(treadmill) -100mph as it's going the opposite direction

Overall speed = 0mph


What the mythbusters vidoe showed was a plane travelling at 0mph relative to the belt, but the same speed as the belt relative to the air, therefore the belt was creating the "thrust" and the air moving over the wings was creating the lift

But the treadmill can only apply force to the wheels which are free moving... If the treadmill were moving at 100mph, it could only make the wheels move at 100mph, not the actual plane. If the speed of the treadmill is unknown, but is at such a speed that it makes the actual plane move backward at 100mph, and the plane is moving forward at 100mph, then the plane would not move... But if the speed of the treadmill is at 100mph, and the plane has a force applied to it that makes it move forwards at 100mph, then it would move forwards, but not at 100mph...

[matt_vtr_15a]

the treadmill could be going at 1000mph, the plane would still take off...

[Ali123]

i think dave has pretty much explained what i had in mind but couldnt put it down into words

and like has been said the treadmill or the rolling runway will only cancel out the turning of the wheels in a way, the plane will still move forward as it normally would

[Era]

I think whoever explained the treadmill and roller skates scenario explained it well.

Imagine you're on the treadmill wearing roller skates, but holding onto the side. You set the treadmill to go 100mph but keep holding the sides - you won't move.

Now your mate comes up behind you and pushes your back, you'd move forwards pretty easily even though the conveyor is moving at 100mph backwards.

Now swap your mate for 2 wings and 4 jet engines, it'd be pretty easy for them to hurl you forwards fast enough, regardless of the conveyor speed and take off.

[KamRacing]

It's not rocket surgery.

One is going forward at Xmph, the other the opposite direction at the same Xmph, the gross speed is 0! x-x = 0, regardless of the value of x

I put all the wrong answers in this thread down to people's lack of being able to read a question properly, rather than their lack of math skill.

Its not that simple maths.

The moving runway only acts on the wheels and bearings. Minimal force is acting to pull the aircraft backwards - instead its primarily rotating the wheels. The aircraft with no power will unlikely to move backwards at the same speed as the runway even if the wheels are.
Think about the old tea cups and tea cloth pulling stunt.
Therefore 100mph of thrust will get the plane moving forward on the runway. If the air speed is then enough to generate lift the plane will take off.

Its still a mind f*** lol

[Mike_Roberts]

Haha everybody's just confusing eachother because not all people have the same understanding of the term eig used.

The original question is also very ambiguous as to what's actually happening...

If the runway was moving at 100mph and the WHEELS were turning at 100mph then it would be stationary but using very little thust. I.e. no airspeed = no lift. Also techincally no groundspeed even though some non-nav instruments would read 200mph as the readings are taken from the anti-skid module at the centre of the wheel (aircraft dependant).

However, if the question was just whether an aircraft would take off on a moving runway, then yes it would. It would take slightly longer to reach take-off airspeed (anything from 80-200mph) because of the extra friction caused by wheel bearings, and some groundspeed reading would show 100mph higher but groundspeed is irrelevant for the majority of aircraft systems.

So basically, most of you are correct, depending on how you understood the question...

[Giraffe]

I think whoever explained the treadmill and roller skates scenario explained it well.

Imagine you're on the treadmill wearing roller skates, but holding onto the side. You set the treadmill to go 100mph but keep holding the sides - you won't move.

Now your mate comes up behind you and pushes your back, you'd move forwards pretty easily even though the conveyor is moving at 100mph backwards.

Now swap your mate for 2 wings and 4 jet engines, it's be pretty easy for them to hurl you forwards fast enough, regardless of the conveyor speed and take off.

And just to add to this, if you let go of the sides, you would move backward, but not at the same speed as the treadmill, as you are being moved backward by virtue of the friction generated on the bearings and contact between wheel and treadmill... So in summary, the object that is on the wheels DOES NOT move at the same speed as the treadmill, only the wheels do.

[baker556]

Everyone's looking at the plane as it has gearing in the wheels.

Think of putting a plane on a rolling road, the plane accelerates its jets to 100mph the rolling road is 100mph, it won't stay their due to the gearing not being in the wheels, the bearings in wheels the fact that the wheels turn freely. The upper thrust from the jet engines would let it take off. The wheels are not important.

[Ali123]

i dont get whats wrong with the question,
the run way is going in the opposite direction to the plane at the same speed at all times

the plane going at 20mph, the run way goes 20mph in the other way, plane goes at 200mph, the runway goes 200mph in the other direction and so on

[Era]

And just to add to this, if you let go of the sides, you would move backward, but not at the same speed as the treadmill, as you are being moved backward by virtue of the friction generated on the bearings and contact between wheel and treadmill... So in summary, the object that is on the wheels DOES NOT move at the same speed as the treadmill, only the wheels do.

Correct, however I interpreted the original question to say that the conveyor moves back at the same speed that the plane moves forwards, so it wouldn't be moving back at all if the plane was sat there with engines idle.

Only once the thrust started pushing the plane forwards would the conveyor begin to move back, but with wheels moving at the speed of the plane forwards + the conveyor moving back (2x the forward speed of the plane through the air).

But yes if the plane was sat there and the conveyor moves back so would the plane, but would need minimal thrust to overcome this and begin moving forwards as normal, regardless of conveyor speed underneath it.

[Giraffe]

i dont get whats wrong with the question,
the run way is going in the opposite direction to the plane at the same speed at all times

the plane going at 20mph, the run way goes 20mph in the other way, plane goes at 200mph, the runway goes 200mph in the other direction and so on

That's still really ambiguous... are you saying that the runway would only move by virtue of the wheels acting against it, or would the runway move by virtue of it's own power?

[Ali123]

That's still really ambiguous... are you saying that the runway would only move by virtue of the wheels acting against it, or would the runway move by virtue of it's own power?

just like the treadmill example, under its own power

[Giraffe]

Correct, however I interpreted the original question to say that the conveyor moves back at the same speed that the plane moves forwards, so it wouldn't be moving back at all if the plane was sat there with engines idle.

Only once the thrust started pushing the plane forwards would the conveyor begin to move back, but with wheels moving at the speed of the plane forwards + the conveyor moving back (2x the forward speed of the plane through the air).

But yes if the plane was sat there and the conveyor moves back so would the plane, but would need minimal thrust to overcome this and begin moving forwards as normal, regardless of conveyor speed underneath it.

Yes, I'm seeing it as the conveyor moving of it's own accord but I seem to be incorrect in that assumption, although not incorrect overall...

If I've got it wrong, then I'd just use the toy car scenario again... put a toy car with free moving wheels on a set of rollers... If the force to move the car were generated through the wheels, the car would not move, if you were to take your hand and push the body of the car, it would move forward by virtue of the fact the force is applied to the body and not wheels...

EDIT: Ok, if the treadmill is moving of it's own power then the only effect is that the wheels spin at the same speed as the runway, the body of the plane is not moving at the same speed of the runway, therefore if the plane is moving at 200mph and the treadmill is moving at 200mph, effectively the plane is moving at 200mph forwards, the wheels are moving at 400mph, and the treadmill is moving at 200mph. Anyone disagree with that, give or take a bit for friction?

Just for the record, I got an A at GCSE physics, then got an E in both AS level physics and maths and mechanics so I accept my knowledge isn't amazing, but it just seems to be common sense :|

[matt_vtr_15a]

Also,

Imagine two scenarios, if the plane wheels had brakes applied the plane and wheels would hurtle back at 100mph...

however

Brakes are not applied in this process therefore wheels just spin and possibly move the plane back slowly as stated due to friction but only very slowly..

[craig180]

Turn this on it's head:

An F1 car creates downforce at 100mph.

Put that F1 car on a rolling road and get it to do 100 mph. The car is showing 100mph, the rolling road has to be doing -100mph in order for the car to stay where it is.

Is the car subject to any downforce? No is the answer.

Exactly the opposite applies to the Aeroplane with lift.

The original statement was that the plane was going X speed in one direction, which is exactly the opposite of the speed of the conveyer belt.

I agree, if the plane ACCELLERATES and travels at a greater speed than the belt is going in the opposite direction, then yes it would eventually take off, but if BOTH ARE TRAVELLING AT THE SAME SPEED IN OPPOSSITE DIRECTIONS THE PLANE WILL NEVER TAKE OFF AS THERE IS NO LIFT

[Mike_Roberts]

i dont get whats wrong with the question,
the run way is going in the opposite direction to the plane at the same speed at all times

the plane going at 20mph, the run way goes 20mph in the other way, plane goes at 200mph, the runway goes 200mph in the other direction and so on

You're making it ambiguous yourself....

Plane going at 20mph? The plane or the wheels? If it's the wheels then it's stationary, if its the plane, then the wheels would be spinning at a rate of 40mph and the plane an airspeed of 20mpg..

[Ali123]

Also,

therefore wheels just spin and possibly move the plane back slowly as stated due to friction but only very slowly..

exactly, so the plane can accelerate under its own power from the jets as normal and take off :drink:

[Era]

Yes, I'm seeing it as the conveyor moving of it's own accord but I seem to be incorrect in that assumption, although not incorrect overall...

If I've got it wrong, then I'd just use the toy car scenario again... put a toy car with free moving wheels on a set of rollers... If the force to move the car were generated through the wheels, the car would not move, if you were to take your hand and push the body of the car, it would move forward by virtue of the fact the force is applied to the body and not wheels...

Yes - for the doubters still I refer to my landing scenario in post #82 - the same would happen on take off but in reverse, it'd be entirely normal (well, as normal as having a conveyor belt as a runway can be).

[Era]

Turn this on it's head:

An F1 car creates downforce at 100mph.

Put that F1 car on a rolling road and get it to do 100 mph. The car is showing 100mph, the rolling road has to be doing -100mph in order for the car to stay where it is.

Is the car subject to any downforce? No is the answer.

Exactly the opposite applies to the Aeroplane with lift.

The original statement was that the plane was going X speed in one direction, which is exactly the opposite of the speed of the conveyer belt.

I agree, if the plane ACCELLERATES and travels at a greater speed than the belt is going in the opposite direction, then yes it would eventually take off, but if BOTH ARE TRAVELLING AT THE SAME SPEED IN OPPOSSITE DIRECTIONS THE PLANE WILL NEVER TAKE OFF AS THERE IS NO LIFT

Using capitals doesn't make you right...you're using an example which is driven through the wheels, in direct interaction with the moving ground, a plane engine is not affected by what the ground is doing, it pushes against the air to move.

So again, it would move forwards up until 180mph, the conveyor would match this backwards at 180mph, causing the freely spinning wheels under the plane to spin at 360mph but the plane would still take off.

[Giraffe]

Turn this on it's head:

An F1 car creates downforce at 100mph.

Put that F1 car on a rolling road and get it to do 100 mph. The car is showing 100mph, the rolling road has to be doing -100mph in order for the car to stay where it is.

Is the car subject to any downforce? No is the answer.

Exactly the opposite applies to the Aeroplane with lift.

The original statement was that the plane was going X speed in one direction, which is exactly the opposite of the speed of the conveyer belt.

I agree, if the plane ACCELLERATES and travels at a greater speed than the belt is going in the opposite direction, then yes it would eventually take off, but if BOTH ARE TRAVELLING AT THE SAME SPEED IN OPPOSSITE DIRECTIONS THE PLANE WILL NEVER TAKE OFF AS THERE IS NO LIFT

The problem here is that the treadmill applies force to the wheels, not the plane... An F1 car is different in that the force is generated through the wheels... if you put the F1 car on rollers then attached a jet to the back of it and it was propelled by the jet, it wouldn't stay on the rollers regardless of the speed that they and the wheels were moving, because you are applying force to the body of the car, which is obviously attached to the wheels... Therefore you have to take in to account the speed of the body of the car, as well as the speed of the wheels and the rollers.

[Giraffe]

I think the problem with your examples Craig is that you are seeing only 2 objects that are moving at speed where there are actually 3... You are seeing the wheels and the runway. The three objects that are moving are the wheels, the runway AND the body of the plane itself...

[Ash1711]

Haha everybody's just confusing eachother because not all people have the same understanding of the term eig used.

The original question is also very ambiguous as to what's actually happening...

If the runway was moving at 100mph and the WHEELS were turning at 100mph then it would be stationary but using very little thust. I.e. no airspeed = no lift. Also techincally no groundspeed even though some non-nav instruments would read 200mph as the readings are taken from the anti-skid module at the centre of the wheel (aircraft dependant).

However, if the question was just whether an aircraft would take off on a moving runway, then yes it would. It would take slightly longer to reach take-off airspeed (anything from 80-200mph) because of the extra friction caused by wheel bearings, and some groundspeed reading would show 100mph higher but groundspeed is irrelevant for the majority of aircraft systems.

So basically, most of you are correct, depending on how you understood the question...

This. The End. :wall:

[craig180]

Lets be realistic a big ass treadmill would create a strong headwind at 100mph planes take off better in a head wind. The plane would take off.

Your looking at it all being stationary well its not its on a treadmill.

Wind created from the treadmill would cause the lift, remember this plane is not stationary i understand the 100mph and 100mph = 0 mph what about the headwind?

http://ffden-2.phys.uaf.edu/211_fall2002.web.dir/josh_palmer/berni%20wing.gif

If 100mph-100mph = 0mph there is no headwind.

I honestly have no idea how much more simple this could be! Are people trying to make it difficult to create a hypothetical situation work???

[craig180]

I think the problem with your examples Craig is that you are seeing only 2 objects that are moving at speed where there are actually 3... You are seeing the wheels and the runway. The three objects that are moving are the wheels, the runway AND the body of the plane itself...

Take the rotation of the wheels out of the equation.

The entire plane is travelling at 100mph, regardless of rotation speed/gearing/smurfs on the runway (which incidentally is just as relevant as the rotation speed and gearing).

The plane is travelling at 100mph (however it's propelled). The belt is travelling at EXACTLY the same speed in the opposite direction.

The overall speed of the plane, relative to EVERYTHING other than the belt is 0.

A lot of people are also confusing 100 mph and -100mph making 200mph combined speed. It isn't. The net speed will always be 100mph. Imagine if the belt stopped. The plane would then travel at 100mph, not 200mph

[baker556]

If 100mph-100mph = 0mph there is no headwind.

I honestly have no idea how much more simple this could be! Are people trying to make it difficult to create a hypothetical situation work???

Stop thinking about the wheels !!

http://kottke.org/06/02/plane-conveyor-belt

You call yourself a mod...

[Era]

Yes but if the relative speed of the plane is 0, then the speed of the belt is 0 (as the question poses) - so you're saying that despite the full thrust from 4 engines going tit-to-a-ton, the plane sits there at 0mph?

[Ali123]

You're making it ambiguous yourself....

Plane going at 20mph? The plane or the wheels? If it's the wheels then it's stationary, if its the plane, then the wheels would be spinning at a rate of 40mph and the plane an airspeed of 20mpg..



right, the BODY of the plane moves forwards at a speed of 100mph, but the runway under its own power moves in the opposite direction at exactly the same speed, what ever the speed the BODY of the plane is doing the runway does the exact same speed as the BODY in the opposite direction

that make it slighlty more clearer?

[craig180]

Stop thinking about the wheels !!

http://kottke.org/06/02/plane-conveyor-belt

You call yourself a mod...

Call yourself intelligent?

Then I read Cecil's answer again this evening and I've changed my mind; I'm fairly certain he's right. For a sufficiently long conveyor belt, that plane is taking off. It doesn't matter what the conveyor belt is doing because the airplane's energy is acting on the air, not the belt.

Which incidentally is wrong..... The air is having zero impact on the plane because it's not technically moving.

That link is about as accurate as most of the posts in this thread ;)

[craig180]

Yes but if the relative speed of the plane is 0, then the speed of the belt is 0 (as the question poses) - so you're saying that despite the full thrust from 4 engines going tit-to-a-ton, the plane sits there at 0mph?

That's called accelleration my friend, which means the speeds aren't equal.

I could go on all day answering these questions but as the saying goes.... you can't educate pork ;)

[blackie_2k5]

Ppl are reading way too much into this

The op's question is flawed,

If the plane is already moving at a speed enough to take of, it will already have taken off

The belt can spin as fast or slow as it wants, the wheels do not propel the plane, the engine pull it through the air

So if the plane was already moving at 100mph and the belt was going at 100mph the opposite way then the wheels would be turning at 100mph but the plane would still already be in the air

So it wouldn't need to take off..

I

[Era]

right, the BODY of the plane moves forwards at a speed of 100mph, but the runway under its own power moves in the opposite direction at exactly the same speed, what ever the speed the BODY of the plane is doing the runway does the exact same speed as the BODY in the opposite direction

that make it slighlty more clearer?

...and the differential between the body of the plane moving forward at 100mph and the conveyor mkving back at 100mph = 200mph, once you get to the body moving forwards at 180mph and the conveyor moving back at 180, the plane takes off as normal.

Don't think I can explain it any other ways.

[baker556]

Call yourself intelligent?

Which incidentally is wrong..... The air is having zero impact on the plane because it's not technically moving.

That link is about as accurate as most of the posts in this thread ;)

I haz degree!

But in a real life situation their would be a strong head wind from a conveyor belt reaching 100mph. Stop thinking of the plane standing still its not, its moving on the belt once the engines reach take of speed it will take off.

With the majority on here and other websites and mythbusters saying it will fly, it will fly.

[craig180]

...and the differential between the body of the plane moving forward at 100mph and the conveyor mkving back at 100mph = 200mph, once you get to the body moving forwards at 180mph and the conveyor moving back at 180, the plane takes off as normal.

Don't think I can explain it any other ways.

No no no no noooooo! The differential is actually 0 as it's not 2 x 100mph it's 100mph and -100mph!!! Basic maths!

If the plane accellerates to 180 and the runways does the same in the opposite direction it's still 0mph, not 360mph!

[craig180]

I haz degree!

But in a real life situation their would be a strong head wind from a conveyor belt reaching 100mph. Stop thinking of the plane standing still its not, its moving on the belt once the engines reach take of speed it will take off.

With the majority on here and other websites and mythbusters saying it will fly, it will fly.

Oh, if we're going to play the qualifications game then bring it on ;)

There is no head wind. The plane isn't moving. The films you have seen are not accurate as the speed of plane/belt are not perfectly matched.

It won't fly.

[Giraffe]

Take the rotation of the wheels out of the equation.

The entire plane is travelling at 100mph, regardless of rotation speed/gearing/smurfs on the runway (which incidentally is just as relevant as the rotation speed and gearing).

The plane is travelling at 100mph (however it's propelled). The belt is travelling at EXACTLY the same speed in the opposite direction.

The overall speed of the plane, relative to EVERYTHING other than the belt is 0.

A lot of people are also confusing 100 mph and -100mph making 200mph combined speed. It isn't. The net speed will always be 100mph. Imagine if the belt stopped. The plane would then travel at 100mph, not 200mph

Man you're wrong because you don't see that you have to factor in the wheels, as the belt affects the wheels, not the plane. If the plane is being thrust forward to 100mph, and the belt is moving backwards at 100mph, the belt is moving the wheels, not the plane.

[Giraffe]

No no no no noooooo! The differential is actually 0 as it's not 2 x 100mph it's 100mph and -100mph!!! Basic maths!

If the plane accellerates to 180 and the runways does the same in the opposite direction it's still 0mph, not 360mph!

NO NO NO. If the plane accelerates to 180 and the runway does the same, then the WHEEL speed is cancelled out so to speak, not the body of the plane itself...

[craig180]

Man you're wrong because you don't see that you have to factor in the wheels, as the belt affects the wheels, not the plane. If the plane is being thrust forward to 100mph, and the belt is moving backwards at 100mph, the belt is moving the wheels, not the plane.

So you're saying the plane isn't moving then?

Just what I've been saying for the last hour ;)

[blackie_2k5]

The wheels mean nothing, they simply support the plane untill it has enough speed to create lift and support it self in the air

[Giraffe]

So you're saying the plane isn't moving then?

Just what I've been saying for the last hour ;)

I'm saying the plane is moving, and by your calculations, the wheels aren't, which is obviously incorrect :|

[craig180]

The wheels mean nothing, they simply support the plane untill it has enough speed to create lift and support it self in the air

Exactly, which at 0mph it can't do...

[baker556]

Its like teaching a child 4+4.

[craig180]

I'm saying the plane is moving, and by your calculations, the wheels aren't, which is obviously incorrect :|

I never said the wheels aren't moving, I said the plane wasn't. For the plane to be doing 0mph the plane theoretically has to be moving at 100mph to cancel out the -100mph of the belt

[Giraffe]

Exactly, which at 0mph it can't do...

You're saying the wheels are moving at 0mph... That would be all well and good if the force to move the plane were being applied to the wheels, but it is not, it's being applied to the body of the plane...

[matt_vtr_15a]

So you're saying the plane isn't moving then?

Just what I've been saying for the last hour ;)

Craig for fuck sake...


Right...

Imagine the treadmill is going at 100mph, the wheels will just spin and the aeroplane will pretty much stay in the same position as the wheels spin freely at a similar speed to the treadmill..

Then imagine the aeroplane fires up its jets, the aeroplane will now propell itself forwards with its thrust forcing the wheels to be dragged along with it...


The speed of the treadmill could be 10000 mph for instance and the plane would still pretty much takeoff as usuall

[Giraffe]

I never said the wheels aren't moving, I said the plane wasn't. For the plane to be doing 0mph the plane theoretically has to be moving at 100mph to cancel out the -100mph of the belt

No. If you put a big rod attached to two structures either side through the plane to hold it in place and put the belt at 100mph, are you telling me that the plane moves in the direction of the belt at 100mph? Obviously the plane doesn't move. The wheels do.

[Chez99]

meh cba reading everyones replys but surely the plane wouldnt take off, the wheels are not a factor in this you could have it on skies and the same applies they are jsut there to stop the plane grinding along the ground (there as support), its the lift under the wings that cause the plane to lift off, along with the thrust of the engines....if there is 0 movement forward the plane with not lift off because it is getting 0 lift because of lack of momevment in the body of the plane.

[Giraffe]

meh cba reading everyones replys but surely the plane wouldnt take off, the wheels are not a factor in this you could have it on skies and the same applies they are jsut there to stop the place grinding along the ground, its the lift under the wings that cause the plane to lift off along with the thrust of the engines....if there is 0 movement the plane with no lift off because it is getting 0 lift because of no momevment.

WRONG. If you put it on skies, the skies are static and do not move. Wheels move. Therefore force from the belt makes the wheels move, which although attached to the plane, move freely. The plane and the wheels move at the same speed because obviously the runway doesn't move, but if the runway moves, it makes the wheels move to the speed the runway is moving, but not the plane itself. If the plane were on skies, obviously the plane would move at the same speed as the runway if there were no counter force...

[matt_vtr_15a]

meh cba reading everyones replys but surely the plane wouldnt take off, the wheels are not a factor in this you could have it on skies and the same applies they are jsut there to stop the place grinding along the ground, its the lift under the wings that cause the plane to lift off along with the thrust of the engines....if there is 0 movement the plane with no lift off because it is getting 0 lift because of no momevment.

don't comment if you aren't going to read the comments that state why this is wrong...

wheels will spin freely enabling the plane to remain in position, ski's would mean that the plane fucks off down the runway as the treadmill drags it's by it's skiis..


for instance...

one of those seaplanes would not take off in this scenario, but an aeroplane will

[Ali123]

meh cba reading everyones replys but surely the plane wouldnt take off, the wheels are not a factor in this you could have it on skies and the same applies they are jsut there to stop the plane grinding along the ground (there as support), its the lift under the wings that cause the plane to lift off, along with the thrust of the engines....if there is 0 movement forward the plane with not lift off because it is getting 0 lift because of lack of momevment in the body of the plane.



youre correct IF there is 0 movement off the body, but there IS movement of the body, the body will move as fast as the jets will propel the body to! it doesnt matter what the wheels are actually doing, they could rotate at 1000mph backwards, but the body of the plane will still move forward

[craig180]

How impossible is it for anyone to understand the concept of 2 moving objects.

Yes, if the plane is travelling at 100mph the wheels are moving. If that plane then drives onto a belt that is doing -100mph then the plane will come to a standstill but the wheels will still be moving as in theory the plane is still travelling at 100mph but becasue the surface under it is also doing 100mph in the opposite direction it is stationary relative to everything else.

Matt, you're bringing a change in speed into the equation. If the plane is doing 100mph on a belt travelling at -100mph then accellerates, of course it's going to move but that wasn't the original scenarion.

the question was IF A PLANE IS DOING EXACTLY THE SAME SPEED AS THE BELT GOING THE OPPOSITE DIRECTION UNDER IT, WILL IT TAKE OFF.

No, because it's not actually moving.

Ignore the wheels, ignore any other factors such as smurfs on the track and look at the simple math. The wheels are turning but the plane isn't moving.

[baker556]

http://www.airplaneonatreadmill.com/

POW, right in the kisser!

[Chez99]

don't comment if you aren't going to read the comments that state why this is wrong...

wheels will spin freely enabling the plane to remain in position, ski's would mean that the plane fucks off down the runway as the treadmill drags it's by it's skiis..


for instance...

one of those seaplanes would not take off in this scenario, but an aeroplane will


I used skii's as an example to support the plane.....So you are telling me if the plane was on stilts, it put its engines on and thrusted it woould take off???? i think not, its the momentum of the wheel moving forward gaining momentum which causes the lift and too take off....if the belt is causing momement in wheels but not in body of the plane so surly its not going to take off. (i did read the first two pages of comments but im not going through 5.)

[baker556]

How impossible is it for anyone to understand the concept of 2 moving objects.

Yes, if the plane is travelling at 100mph the wheels are moving. If that plane then drives onto a belt that is doing -100mph then the plane will come to a standstill but the wheels will still be moving as in theory the plane is still travelling at 100mph but becasue the surface under it is also doing 100mph in the opposite direction it is stationary relative to everything else.

Matt, you're bringing a change in speed into the equation. If the plane is doing 100mph on a belt travelling at -100mph then accellerates, of course it's going to move but that wasn't the original scenarion.

the question was IF A PLANE IS DOING EXACTLY THE SAME SPEED AS THE BELT GOING THE OPPOSITE DIRECTION UNDER IT, WILL IT TAKE OFF.

No, because it's not actually moving.

Ignore the wheels, ignore any other factors such as smurfs on the track and look at the simple math. The wheels are turning but the plane isn't moving.

Your looking at the wheels again FFS :panic:

[baker556]

I used skii's as an example to support the plane.....So you are telling me if the plane was on stilts, it put its engines on and thrusted it woould take off???? i think not, its the momentum of the wheel moving forward gaining momentum which causes the lift and too take off....if the belt is causing momement in wheels but not in body of the plane so surly its not going to take off. (i did read the first two pages of comments but im not going through 5.)

It would take off, the wheels do not drive the plane.

[Giraffe]

How impossible is it for anyone to understand the concept of 2 moving objects.

Yes, if the plane is travelling at 100mph the wheels are moving. If that plane then drives onto a belt that is doing -100mph then the plane will come to a standstill but the wheels will still be moving as in theory the plane is still travelling at 100mph but becasue the surface under it is also doing 100mph in the opposite direction it is stationary relative to everything else.

Matt, you're bringing a change in speed into the equation. If the plane is doing 100mph on a belt travelling at -100mph then accellerates, of course it's going to move but that wasn't the original scenarion.

the question was IF A PLANE IS DOING EXACTLY THE SAME SPEED AS THE BELT GOING THE OPPOSITE DIRECTION UNDER IT, WILL IT TAKE OFF.

No, because it's not actually moving.

Ignore the wheels, ignore any other factors such as smurfs on the track and look at the simple math. The wheels are turning but the plane isn't moving.

Because there is 3 moving objects in this scenario? The plane, the wheels and the treadmill?

The part I've put in italics and underlined is exactly why you are incorrect. The only way you would ever be correct is if the plane were travelling at 100mph by virtue of force being applied through wheels. The plane is travelling at 100mph because of force applied to the body of the plane, the wheels just have to turn at that speed and would continue to do so regardless of the surface underneath or however it is moving.

[matt_vtr_15a]

Acceleration doesn't come in to it, I am removing myself from this thread cause it's melting my brain...

The wheels will spin at -100mph on the treadmill I agree..

The plane moving at +100mph would create 0mph I also agree..

But the wheels will be dragged along in theory as they are attached to the plane and free moving, the wheels couldn't prevent the the aeroplane from taking off they pretty much have no choice..

Imagine you're on a treadmill with a jet strapped to you and wheels on your feet like rollerblades...

Let the treadmill reach it's 100mph and you as a person would be doing 0mph but your wheels doing 100mph...

Now set your jets to the equal force to create 100mph of thrust so that the treadmill and your speed is equal and you would have to move forwards...

otherwise what happens to that energy???

[craig180]

http://www.airplaneonatreadmill.com/

POW, right in the kisser!

Here are the three core facts that are rock-solid:


A) If the plane remains stationary relative to the ground, it will not take off.B) If the plane moves relative to the ground, it will take off.
C) The person operating the conveyor belt cannot by himself make the plane remain stationary relative to the ground.

So you're admitting defeat then?

[Chez99]

It would take off, the wheels do not drive the plane.

I know the wheels do not drive it, its the engine's/turbines....but from a stationary point, it would take off as it does not need wheels to move it but it still needs to gain some sort of momentum to make lift? no?

[craig180]

Your looking at the wheels again FFS :panic:

Yet you highlighted me saying IGNORE THE WHEELS?!!!!

Thought you had a degree??!!!!!!!

[baker556]

So you're admitting defeat then?

Read the whole site.

[Giraffe]

So you're admitting defeat then?

IF the plane remains stationary. The conveyor affects the wheels, not the plane. The plane and the wheels have to be seen as two different objects. A plane is moved by virtue of a force being applied to the body of the plane, not the wheels. If you apply a force to the wheels, it means absolutely nothing because the force is not being applied to the wheels (that propels the plane forwards that is)...

[baker556]

Yet you highlighted me saying IGNORE THE WHEELS?!!!!

Thought you had a degree??!!!!!!!

I highlighted yourself ignoring the wheels then bringing the wheels back into the equation.

The thrust plays the vital role not the wheels.

[Giraffe]

I know the wheels do not drive it, its the engine's/turbines....but from a stationary point, it would take off as it does not need wheels to move it but it still needs to gain some sort of momentum to make lift? no?

Why wouldn't it gain momentum?

[craig180]

Read the whole site.

I did and it confirms EVERY part of my argument

[Chez99]

Why wouldn't it gain momentum?

well it would but it would just scrape accross the ground/surface till it it had enough wind/air passing through to cause the lift

[baker556]

I did and it confirms EVERY part of my argument

What that 100mph - 100mph = 0mph.

This is too simplistic view of the situation as a whole, there are other factors.

The site confirms it would take off, so you obviously didn't read it.

Stop thinking of a stationary plane, its on a conveyor belt in which moves, the whole argument is if the plane is on a conveyor belt will it take off?

When the "no-flys" saw the Mythbusters episode, they all complained that it wasn't done properly, because the plane didn't remain stationary. But think about it for a moment. No, really think about it, don't just spout about Bernoulli's principle and airflow and all that. In what possible scenario would the plane actually stay still? The only way this can happen is if the pilot is trying to stay still, and this only happens if he just barely applies the throttle, making no attempt to take off. This makes no sense. Either you're trying to prevent him from taking off with your clever and misinformed use of a conveyor belt, or he's trying to defy physics by taking off in a too-small area. There is no scenario in which the plane would realistically stay still. We know what would happen if it did - it would sit on the runway, not taking off, and we'd all stare at each other in an all-too-short silence punctuated by loud exclamations of "I told you so!". But that's not really what the thought experiment is getting at, no matter how you reasonably interpret it. Luckily for all of us, if we agree on the interpretation, reasonable or not, we should all agree on the answer.

So let's get back to the next great internet debate, shall we?

[Giraffe]

well it would but it would just scrape accross the ground/surface till it it had enough wind/air passing through to cause the lift

The jet engines of a plane apply force to the body of the plane which is attached to the wheels. No force is applied to the wheels directly. The treadmill would apply force to the wheels. Therefore the force being applied to the wheels in no way cancels out any force applied to the body of the plane. The wheels and the plane have to be classed as two separate objects so to speak.

[devilsadvocate]

Surely the answer is.....if there is enough airflow passing over/under the wings to generate the lift required then the plane will be able to take off.

If the tredmil is doing 10mph and the plane is doing the same then it will not take off as there will not be enough lift being generated.

If the treadmill and plane are both doing 200mph (even if the plane is not moving forward) then there will be enough airflow passing over/under the wings to allow the plane to take off. The pilot pulls back on the control column and the plane lifts into the air.

This is assuming the plane is not able to increase its speed using thrust from the engines. If the thrust from the engines can be increased then the plane will take off with ease.

The plane does not need to move foward to take off, it simply needs enough airflow passing over/under the wings.

[Chez99]

Once i see a video with proof of this, i will admit defeat, untill i do im not, because im a cnut :y:

[Viper]

It would take off and the wheels would end up doing a massive speed due to the moving ground plus the thrust from the engines

Simples.

[Proffitt]

Once i see a video with proof of this, i will admit defeat, untill i do im not, because im a cnut :y:

Here you go...

watch this craig

http://www.youtube.com/watch?v=4owlyCOzDiE

[craig180]

What that 100mph - 100mph = 0mph.

This is too simplistic view of the situation as a whole, there are other factors.

The site confirms it would take off, so you obviously didn't read it.

Stop thinking of a stationary plane, its on a conveyor belt in which moves, the whole argument is if the plane is on a conveyor belt will it take off?

That site confirms the plane cannot take off given THIS scenario.

Viper you're wrong. I'm off to a meeting now. Speak to you apes later xxx

[Keefo]

soooo many people saying it wouldnt take off... when it clearly would.

Treadmill will just spin the wheels, the engine forces the body of the plane to move NOT via the wheels, but via thrust generated by basically firing air out the back so the fact the wheels are spinning backwards means fuck all.

the plane would move forward as if the floor was stationary, then off it would fly.

[GC_Belfast]

Saxo180, y u so stupid?

[Giraffe]

That site confirms the plane cannot take off given THIS scenario.

Viper you're wrong. I'm off to a meeting now. Speak to you apes later xxx

The scenario that a conveyor moves at the same speed as an object of which it cannot directly affect? That's the whole thing here, the treadmills speed is matched to an object that it has no direct influence over. The treadmill influences the speed of the wheels, not the plane. That's where you go wrong.

[blackie_2k5]

Craig how can you not understand this lol?

Read the tread mill and toy car example again,

[K17NEY]

Yes, The only difference the runway would have is making the wheels spin twice as fast, As already mentioned, The planes forward thrust is created by the engines, Not the wheels.

[Ash1711]

This has bene going on for far too long - there are 2 answers... Yes and No.

Yes - if the plane is being propelled by the jet engines then the plane would take off because the engine would push the body of the plane through the air at a speed high enough to create lift. The moving runway underneath the plane would have no effect - as others have said the wheels would only be there to keep the body of the plane off the runway.

No - if the plane is being propelled by the wheels (imagine an F1 car with wings attached rather than a plane) then the plane/car wouldnt be moving anywhere which is where Saxo 180 is coming from.

It all depends on the question and I think we'd need more information to have an answer that clearly falls on one side. Why does this have to continue? lol

[smiith]

The plane wouldnt move or take off.. Its like when a car is on a rolling road, it is propelling itself at whatever speed, but its not actually moving, so you get no down force, nor any air flow over the car..

[Ali123]

The plane wouldnt move or take off.. Its like when a car is on a rolling road, it is propelling itself at whatever speed, but its not actually moving, so you get no down force, nor any air flow over the car..

yes, but with a car the power is through the wheels
but on a plane the wheels are just there, they do nothing in terms of moving the plane, but reduce friction and stop the plane etc, their propulsion is down to the jets pushing the BODY along

[craig180]

So what you guys are saying (and clearly unable to understand the original theory concept and question posed) is that the plane is travelling at 100mph relative to the air and 200mph relative to the conveyor?

If its travelling at 200 relative to the belt then of course it would take off as it has 100mph of positive momentum but it wouldn't be travelling at the same speed as the belt, therefore rendering this argument invalid.

If the plane is stationery relative to everything but the belt, it is travelling at 100mph in the opposite direction as the belt regardless of whether this is down to thrust or zero resistance in the wheel bearings. Either way, relative to the belt it is travelling at 100mph

[Giraffe]

So what you guys are saying (and clearly unable to understand the original theory concept and question posed) is that the plane is travelling at 100mph relative to the air and 200mph relative to the conveyor?

If its travelling at 200 relative to the belt then of course it would take off as it has 100mph of positive momentum but it wouldn't be travelling at the same speed as the belt, therefore rendering this argument invalid.

If the plane is stationery relative to everything but the belt, it is travelling at 100mph in the opposite direction as the belt regardless of whether this is down to thrust or zero resistance in the wheel bearings. Either way, relative to the belt it is travelling at 100mph

The belt affects the speed of the wheels. The speed of the wheels does not equal the speed of the plane. Watch the video that matt posted and then profitt quoted.

The problem is with the question itself Craig. The fact that the belt moves at the same speed as the plane is largely irrelevant because the belt does not affect the plane. The belt affects the wheels, which are under no direct force. If you removed the wheels entirely, just imagine they are not there at all and the plane is now floating above the runway for whatever reason, it turns it's engines on and goes up to 100mph, the belt also moves up to 100mph. The belt moves the same speed as the body of the plane, but in the opposite direction, but it's pointless because the runway doesn't directly affect the plane at all, only the wheels, which are completely irrelevant as to whether or not the plane moves... You could replace the wheels with tank track things, it makes no odds, they move only as a consequence of being attached to the body of the plane, of which the runway does not come in to contact...

[craig180]

The belt affects the speed of the wheels. The speed of the wheels does not equal the speed of the plane. Watch the video that matt posted and then profitt quoted.

Speed is relative. If you have 2 space ships in space side by side, both doing 7000 mph, they are both doing 70000mph relative to everything around but could appear to both be stationary to one another.

It's all about what your speed is relative to. The original post implied speed between the plane and belt being relative to one another, not the air, or the surrounding land or pappa smurf, therefore my answer is correct

[stealthVTS]

Surely lift on the planes wings would be necessary? I thought that is how they take off in the first place? the speed of the floor has nothing to do with it........

[craig180]

Surely lift on the planes wings would be necessary? I thought that is how they take off in the first place? the speed of the floor has nothing to do with it........

Correct. :y:

[Jungle]

So after 9 pages saxo180 has admitted he is wrong, in a very roundabout way. Well thank fuck for that can we move an to something else now.

[craig180]

So after 9 pages saxo180 has admitted he is wrong, in a very roundabout way. Well thank fuck for that can we move an to something else now.

Where have I admitted to being wrong? :err:

The answer is if the plane and belt are moving at the same speed, in opposite directions relative to each other the plane cannot take off.

[stealthVTS]

Where have I admitted to being wrong? :err:

The answer is if the plane and belt are moving at the same speed, in opposite directions relative to each other the plane cannot take off.

Ding Ding Ding, WE HAVE A WINNER!!!!!!!!

I fail to see where you have stated anything other than this in the entire thread but hey! :)

[KamRacing]

Lets be glad you are not an engineer lol

[craig180]

Lets be glad you are not an engineer lol

Qualified to be one should I have chosen that path ;)

[Viper]

If its travelling at 200 relative to the belt then of course it would take off as it has 100mph of positive momentum but it wouldn't be travelling at the same speed as the belt, therefore rendering this argument invalid.

If the plane is stationery relative to everything but the belt, it is travelling at 100mph in the opposite direction as the belt regardless of whether this is down to thrust or zero resistance in the wheel bearings. Either way, relative to the belt it is travelling at 100mph

The only way the plane is moving at 100mph is if the brakes are on. Then it's doing 100mph backwards...

If the brakes are off, it's freewheeling. Then you add the 100mph of thrust from the glorious engines which propels the aircraft forwards as it wasn't previously being moved back.

[craig180]

The only way the plane is moving at 100mph is if the brakes are on. Then it's doing 100mph backwards...

If the brakes are off, it's freewheeling. Then you add the 100mph of thrust from the glorious engines which propels the aircraft forwards as it wasn't previously being moved back.

Nope. If it's still relative to the air then it's travelling 100mph relative to the belt

Freewheeling or not, it's still travelling at a speed.

Are you saying when you coast your car down a hill (ie freewheeling) you're not actually travelling at any speed?

[Ash1711]

Nope. If it's still relative to the air then it's travelling 100mph relative to the belt

Freewheeling or not, it's still travelling at a speed.

Are you saying when you coast your car down a hill (ie freewheeling) you're not actually travelling at any speed?

No, he's saying if you was coasting your car down a hill that is also a belt pulling the car back up the hill at the same speed it was going down (just like the plane question) then you're not actually travelling at any speed.

I do realise this is impossible if a hill and wheels are involved - just sayin'

[JoshB]

If the runway (a treadmill) was travelling at 100mph in one direction, and you just rested a plane on the runway. Which way would the plane go?

[baker556]

You just don't get it.

The conveyor belt is moving backwards at 100mph the wheels on the plane are moving 100mph backward, however the body of the plane is not doing 100mph, its standing still at 0mph.

As there is no gearing towards the wheels as soon as the engines kick in fully it would take off.

It takes less effort to just hold the plane on that conveyor belt than you would think, as there is no gearing the relative force all lie within the jet engines.

Its abit like putting a hover craft on the conveyor belt the wind created from the fan would eventually push it forward. The jet engines will just push it forward and up. Even if you matched the speed of the jet engines they are tremendously powerful it would just take off, its not about matching the speed through the wheels, the jet engines use the air as the drive not the treadmill.

[craig180]

If the runway (a treadmill) was travelling at 100mph in one direction, and you just rested a plane on the runway. Which way would the plane go?

Depends which way the plane was facing ;)

[JoshB]

You just don't get it.

The conveyor belt is moving backwards at 100mph the wheels on the plane are moving 100mph backward, however the body of the plane is not doing 100mph, its standing still at 0mph.

As there is no gearing towards the wheels as soon as the engines kick in fully it would take off.

It takes less effort to just hold the plane on that conveyor belt than you would think, as there is no gearing the relative force all lie within the jet engines.

Its abit like putting a hover craft on the conveyor belt the wind created from the fan would eventually push it forward. The jet engines will just push it forward and up. Even if you matched the speed of the jet engines they are tremendously powerful it would just take off, its not about matching the speed through the wheels, the jet engines use the air as the drive not the treadmill.

Just answer my question.

[craig180]

Just answer my question.

Fucking LOL

[Giraffe]

If the runway (a treadmill) was travelling at 100mph in one direction, and you just rested a plane on the runway. Which way would the plane go?

It travels in the direction of the treadmill, but you tell me what speed it travels at...

[Viper]

The plane would be moved back a bit, but nowhere near 100mph which means that the 100mph forward thrust would allow air flow (which Craig keeps bitching about) over the wings.

The MOST important question here is what is the aircraft?

[craig180]

The plane would be moved back a bit, but nowhere near 100mph which means that the 100mph forward thrust would allow air flow (which Craig keeps bitching about) over the wings.

The MOST important question here is what is the aircraft?

Not if the speed of the plane relative to the air still equals 0mph ;)

There will be thrust, yes, but there will be no lift.

[e8_pqck]

Doesn't thrust create air flow?
It pulls air in from the front and shoots it out the back.
This pulls the air over the wings and creates the much needed lift.

this is the same reason harrier jump jets can move forward after a vertical take off else they would just drop to the floor when they begin to move forward.

[saxo-parts]

no airflow over the aerofoil=no lift=no take off

[craig180]

Doesn't thrust create air flow?
It pulls air in from the front and shoots it out the back.
This pulls the air over the wings and creates the much needed lift.

this is the same reason harrier jump jets can move forward after a vertical take off else they would just drop to the floor when they begin to move forward.

Some do, you're right but not enough to generate lift on their own. They use the engines to create momentum/horizontal speed and that in turn pushes the plane through the air crating lift.

[saxo-parts]

can produce all sorts of mathematical formula bollocks for lift over a wing relative to airflow and forward motion from my apprentice days but i never understood it lol

[saxo-parts]

Some do, you're right but not enough to generate lift on their own. They use the engines to create momentum/horizontal speed and that in turn pushes the plane through the air crating lift.

harrier is a different kettle of fish, thrust is directed via variable nozzles enabling it to do all sorts of things,like use the engines to actually scrub speed, handy for letting an enemy overshoot so you can get behind him, as the argentinians found out 30 years ago

[craig180]

harrier is a different kettle of fish, thrust is directed via variable nozzles enabling it to do all sorts of things,like use the engines to actually scrub speed, handy for letting an enemy overshoot so you can get behind him, as the argentinians found out 30 years ago

Dont they also have rotating jets allowing them to direct thrust?

[Ali123]

Dont they also have rotating jets allowing them to direct thrust?

they do indeed

[saxo-parts]

Dont they also have rotating jets allowing them to direct thrust?

thats what the nozzles are, in place of a conventional tailpipe on a general gas turbine, the thrust is diverted via ducting to the 4 nozzles,rather then just the 1 straight out of the back.

[e8_pqck]

But the harrier is the exact same principal and it takes off.

the engines will be pointing the same way when they move forward.

Solved.

[saxo-parts]

think you're missing the point, harriers exhaust nozzles rotate, guiding thrust, ie, pointing downwards, guiding thrust down which raises it off the ground, to move forwards the nozzles rotate to point rearwards and the thrust moves the aircraft forward, however thrust alone will not move it forwards and keep it airborne, for that you need lift, which is produced by a pressure differential over an aerofoil section, in the case of an aircraft its wing. Lift is dependant on the airspeed over the aerofoiland its angle of attack, ie the angle of the centre line of the aerofoil to the relative direction of the airflow. If the angle of attack is too great and the airspeed too low, you get a condition known as "stall", which is nothing like stalling your car and has far more serious consequences then looking daft outside the sixth form college ie. you crash and die

[Lukus-vtr]

I haven't read through all 10 pages so I don't know if this has already been said, but it doesn't matter how fast the wheels are spinning on an aircraft for it to take to take off but the amount of air going over the wings. An aircraft such as a 747 will have flaps set at 20 degress to get optimum angle of attack to get maximum air flow over the aero foil over and under the wing. An aircraft that has a head wind will be able to take off at much slower speeds as more air is forced over the wings, so if an aircraft is travelling at 100 mph and there is a headwind of 15mph then the Indicated airspeed would be 115mph but the true air speed is still 100mph. So theoretically if the wind speed was very high then an aircraft can take off with out moving.

The engines create thrust/propulsion. The wings, ailerons and flaps create lift.

http://www.youtube.com/watch?v=cHhZwvdRR5c

[Mochachino]

No it wont.

[Mr_P]

I haven't read through all 10 pages so I don't know if this has already been said, but it doesn't matter how fast the wheels are spinning on an aircraft for it to take to take off but the amount of air going over the wings. An aircraft such as a 747 will have flaps set at 20 degress to get optimum angle of attack to get maximum air flow over the aero foil over and under the wing. An aircraft that has a head wind will be able to take off at much slower speeds as more air is forced over the wings, so if an aircraft is travelling at 100 mph and there is a headwind of 15mph then the Indicated airspeed would be 115mph but the true air speed is still 100mph. So theoretically if the wind speed was very high then an aircraft can take off with out moving.

But the plane would be able to move forward on a runway that was moving backwards at the same speed.

[e8_pqck]

think you're missing the point, harriers exhaust nozzles rotate, guiding thrust, ie, pointing downwards, guiding thrust down which raises it off the ground, to move forwards the nozzles rotate to point rearwards and the thrust moves the aircraft forward, however thrust alone will not move it forwards and keep it airborne, for that you need lift, which is produced by a pressure differential over an aerofoil section, in the case of an aircraft its wing. Lift is dependant on the airspeed over the aerofoiland its angle of attack, ie the angle of the centre line of the aerofoil to the relative direction of the airflow. If the angle of attack is too great and the airspeed too low, you get a condition known as "stall", which is nothing like stalling your car and has far more serious consequences then looking daft outside the sixth form college ie. you crash and die

Been watching a few vids now, and i quite agree with this statement.

[blackie_2k5]

What came first

Lager or kebab?

[Mr_P]

What came first

Lager or kebab?

Lager always goes in first.
Kebab always comes back out first.

[blackie_2k5]

Lager always goes in first.
Kebab always comes back out first.

I suppose it depends which end it comes out :p

[Mr_P]

I suppose it depends which end it comes out :p

Touché
:drink:

[Mezza]

Mythbusters did this if im correct, didn't read whole thread so if someone pointed this out, then touche to you.

I'll just leave this here...
http://www.youtube.com/watch?v=YORCk1BN7QY

[matt_vtr_15a]

Some people seriously need to admi hey are wrong... You've been proven wrong already even with videos...

[Mike_Roberts]

think you're missing the point, harriers exhaust nozzles rotate, guiding thrust, ie, pointing downwards, guiding thrust down which raises it off the ground, to move forwards the nozzles rotate to point rearwards and the thrust moves the aircraft forward, however thrust alone will not move it forwards and keep it airborne, for that you need lift, which is produced by a pressure differential over an aerofoil section, in the case of an aircraft its wing. Lift is dependant on the airspeed over the aerofoiland its angle of attack, ie the angle of the centre line of the aerofoil to the relative direction of the airflow. If the angle of attack is too great and the airspeed too low, you get a condition known as "stall", which is nothing like stalling your car and has far more serious consequences then looking daft outside the sixth form college ie. you crash and die

At last..somebody else who understands basic aerodynamic principles! Canna beat a twin shaft, high flow bypass pegasus turbofan ;)

[craig180]

Some people seriously need to admi hey are wrong... You've been proven wrong already even with videos...

Who? Me?

That video doesn't show what is asked in the original post. That shows a plane travelling faster than the belt.

[blackie_2k5]

Lock this thread please :)

[Giraffe]

Who? Me?

That video doesn't show what is asked in the original post. That shows a plane travelling faster than the belt.

Do you understand that the runway affects the wheels and not the plane? That means that the PLANE can travel X speed in whatever direction it wants and if the belt wants to travel the same speed in the opposite way, it makes no difference, because it's not slowing the plane down what so ever. The plane will still move...

[Viper]

Not if the speed of the plane relative to the air still equals 0mph ;)

There will be thrust, yes, but there will be no lift.

You really are being dense today.

[Giraffe]

You really are being dense today.

I think he's trolling. He absolutely must be. There have been videos posted up that show without any doubt what so ever that as long as the plane is moving forwards at a certain speed, the speed of the runway makes absolutely no difference, and yet still disputes it...

Seriously Craig, the plane could be moving at 50mph forwards and the runway moving 100mph in the opposite direction, the plane would still move forwards.

[Viper]

I think he's trolling. He absolutely must be. There have been videos posted up that show without any doubt what so ever that as long as the plane is moving forwards at a certain speed, the speed of the runway makes absolutely no difference, and yet still disputes it...

Seriously Craig, the plane could be moving at 50mph forwards and the runway moving 100mph in the opposite direction, the plane would still move forwards.

I thought he was trolling earlier but I think we have proved he's actually retarded.

[Rogue_Shadow]

Seriously! This thread is STILL GOING!
You should feel ashamed this thread grows while the Hot Bird Thread (http://www.saxperience.com/forum/showthread.php?t=340736&page=115) lays untouched.
:panic:

[Viper]

Oh wow, I have just seen the video you mentioned!!

Craig, how can you even contemplate arguing the point after that video.

Unless this is the best troll you've done.

Either way I think you're a gaylord.

[blackie_2k5]

i think by the extent he's published his view..its pretty clear hes been sniffing yorkshire tea all day

and has the bath salt variety view.. on reality at the min

he'll chew someone's face off later..naked.... on the high street, then realise the plane should already be in flight..serving a roast with puds..and that all he said is irrelevant against the arguement :y:

i still havent watched the vid..i refuse to believe its a troll :p

[craig180]

I think he's trolling. He absolutely must be. There have been videos posted up that show without any doubt what so ever that as long as the plane is moving forwards at a certain speed, the speed of the runway makes absolutely no difference, and yet still disputes it...

Seriously Craig, the plane could be moving at 50mph forwards and the runway moving 100mph in the opposite direction, the plane would still move forwards.

Relative to what though?

The implication in the original post and that of the previous 600 threads of exactly the same "problem" is that the plane and belt are moving relative to each other which came about many years ago when someone suggested that planes could take off from a ship using a conveyor belt rather than being propelled by a release mech.

It has since been proved with simple maths and a basic grasp of physics that it is in fact impossible. The problem is many people fail to grasp the term "relative".

Regardless of whether a plane is free wheeling because of zero friction in the bearings etc or whether it is (more likely) being held at the same point relative to everything else around due to thrust, the plane is still moving relative to the belt at exactly the opposite speed

Honestly, I'm not trolling, nor am I wrong. I'm simply trying to get people to understand that speed is relative only to another fixed point.

Imagine this: you stand still. How fast are you going?

The answer could be 0mph, or it could be 1000mph or it could be a number even greater. How? Well if you're measuring against the earth as a fixed point, you are in fact standing still, therefore travelling 0mph. If you consider the earth rotates at approx 1000mph, then why not that speed? Or using another galaxy as the point of reference? Many millions of mph...

The point is as I outlined above. The problem was posed on the basis you can get a plane to a speed which it would normally be capable of flying, but without it actually moving anywhere. Therefore the speed is relative to the moving surface below it.

This has tricked many people for many years into thinking about other variables.

Does this make sense? Sorry if not. I'm on my mobile and I've had some beer.

[Giraffe]

Relative to what though?

The implication in the original post and that of the previous 600 threads of exactly the same "problem" is that the plane and belt are moving relative to each other which came about many years ago when someone suggested that planes could take off from a ship using a conveyor belt rather than being propelled by a release mech.

It has since been proved with simple maths and a basic grasp of physics that it is in fact impossible. The problem is many people fail to grasp the term "relative".

Regardless of whether a plane is free wheeling because of zero friction in the bearings etc or whether it is (more likely) being held at the same point relative to everything else around due to thrust, the plane is still moving relative to the belt at exactly the opposite speed

Honestly, I'm not trolling, nor am I wrong. I'm simply trying to get people to understand that speed is relative only to another fixed point.

Imagine this: you stand still. How fast are you going?

The answer could be 0mph, or it could be 1000mph or it could be a number even greater. How? Well if you're measuring against the earth as a fixed point, you are in fact standing still, therefore travelling 0mph. If you consider the earth rotates at approx 1000mph, then why not that speed? Or using another galaxy as the point of reference? Many millions of mph...

The point is as I outlined above. The problem was posed on the basis you can get a plane to a speed which it would normally be capable of flying, but without it actually moving anywhere. Therefore the speed is relative to the moving surface below it.

This has tricked many people for many years into thinking about other variables.

Does this make sense? Sorry if not. I'm on my mobile and I've had some beer.

Right hang on. Are you saying that if the belt is moving at 200mph, and the plane is using enough thrust to hold it stationary, then the plane must be moving 200mph in the opposite direction?

[craig180]

Right hang on. Are you saying that if the belt is moving at 200mph, and the plane is using enough thrust to hold it stationary, then the plane must be moving 200mph in the opposite direction?

Yes. Relative to the belt, as per post #1

[Giraffe]

Yes. Relative to the belt, as per post #1

So I'm on a treadmill on my roller skates, the treadmill is set at a speed of 100mph and I hold on to the sides. I'm travelling at 100mph in the opposite direction relative to the treadmill?

[craig180]

So I'm on a treadmill on my roller skates, the treadmill is set at a speed of 100mph and I hold on to the sides. I'm travelling at 100mph in the opposite direction relative to the treadmill?

Yes. Are you taking the piss now or have you grasped the concept?

If the belt suddenly stops, assuming no resistance the plane would propel forward at 200mph.

[Viper]

Right hang on. Are you saying that if the belt is moving at 200mph, and the plane is using enough thrust to hold it stationary, then the plane must be moving 200mph in the opposite direction?

Yes. Relative to the belt, as per post #1

Well done Craig. Proof that you're wrong. The plane will NOT be moving at that speed in the direction of the belt because THE WHEELS WILL MOVE FREELY. Therefore when the plane thrusts, it pushes itself forwards, because it is thrusting forwards from the AIR, not from the belt.

Yes. Are you taking the piss now or have you grasped the concept?

If the belt suddenly stops, assuming no resistance the plane would propel forward at 200mph.

It really, really would not. The wheels would just stop spinning like fuck.

[blackie_2k5]

craig your arguement is still invalid

if the plane is going at the same speed as the treadmill..in the opposite direction, the plane will still propel at X speed

and the wheels will still turn at X speed

the plane is already moving..if enough lift is created, it will take off..the wheels will still be free to be powered by the treadmill

[craig180]

Well done Craig. Proof that you're wrong. The plane will NOT be moving at that speed in the direction of the belt because THE WHEELS WILL MOVE FREELY. Therefore when the plane thrusts, it pushes itself forwards, because it is thrusting forwards from the AIR, not from the belt.



It really, really would not. The wheels would just stop spinning like fuck.

You are adding a further variable to the equation.

What you are saying is that the plane is already travelling at 100mph on the treadmill through freewheeling. You then thrust a further 100mph. Therefore your relative speed is twice that of the treadmill and not equal.

Of course it would then fly because it has positive momentum.

This is what appears to have caught most people out. I actually thought better of you if I'm honest ;)

[Giraffe]

Yes. Are you taking the piss now or have you grasped the concept?

If the belt suddenly stops, assuming no resistance the plane would propel forward at 200mph.

See, that's where I struggle. So if someone pulls the plug on the treadmill and it switches off, do I then fly forwards at 100mph? No, the wheels just stop spinning... same as the plane would not fly forwards at 200mph... If it did, they could put at plane on a small conveyor on a runway, do exactly what you've just said, then just switch the conveyor off, and boom, the plane is moving fast enough to get in the air... The wheels would just stop spinning and the plane would begin to move forwards slowly...

[Giraffe]

You are adding a further variable to the equation.

What you are saying is that the plane is already travelling at 100mph on the treadmill through freewheeling. You then thrust a further 100mph. Therefore your relative speed is twice that of the treadmill and not equal.

Of course it would then fly because it has positive momentum.

This is what appears to have caught most people out. I actually thought better of you if I'm honest ;)

How can a plane travel at 100mph through freewheeling? :|

[craig180]

It really, really would not. The wheels would just stop spinning like fuck.

so where is the thrust energy dispersed then? Forward propulsion, that's where

[craig180]

See, that's where I struggle. So if someone pulls the plug on the treadmill and it switches off, do I then fly forwards at 100mph? No, the wheels just stop spinning... same as the plane would not fly forwards at 200mph... If it did, they could put at plane on a small conveyor on a runway, do exactly what you've just said, then just switch the conveyor off, and boom, the plane is moving fast enough to get in the air... The wheels would just stop spinning and the plane would begin to move forwards slowly...

Either way you're not going to fly!!!!!!!!

[Giraffe]

Either way you're not going to fly!!!!!!!!

Surely it's the wheels on the plane that are moving relative to the treadmill or the runway, not the actual plane itself though?

[blackie_2k5]

so where is the thrust energy dispersed then? Forward propulsion, that's where

think of it as separate units,


you have a small plane..crop duster type wanker..


its travelling at 100mph through the air..pulling itself along by the propulsion of the engine...fine?


its got fixed landing gear, free wheels with loose bearings...sticking out the bottom as per

NOW.....you have a treadmill on the ground, the treadmill is in reverse, going at a fixed 100mph,

you lift the treadmill on a platform...all the way up till it touches the flying plane's wheels..

what happens??

the plane wheels start going in reverse at about 100mph (forget friction and drag for the purpose of this explanation)

because they arent driven by the plane, the belt now controls them,

so are you saying the plane will now fallout of the sky??

[blackie_2k5]

before i get bombarded....we're on a never ending treadmill...as it would have to be..they are both constants ( the plane speed and treadmill)

[e8_pqck]

its true, the thrust will move the plane forward - it doesnt matter what the wheels are doing as the thrust acts on air not the wheels.

think of it like this

attach wheels to your feet and a ladder above you.
turn on treadmill to 100mph - the wheels will spin
now pull yourself along the rungs of the ladder

it doesnt matter how fast the wheels turn as they are not pulling you forward

same as jet engines - the wheels dont matter

its not a case of the wheels matching the speed of the plane - they physically cant - it doesnt matter, you cant stop the plane moving forward as it is pulled along through the air - i.e. the ladder.

[matt_vtr_15a]

You keep ignoring key points people raise as well...

Treadmill speed = -100

Aeroplane wheel speed = -100 however this will not move the plane, the wheels just go into a spin ( if the plane does move its minimal) certainly not close to the treadmill speed..

So currently the aeroplane speed is still around 0mph, and the plane is not in motion even though the wheels are spinning...

I now power the plane up to a speed (any speed equal to or less than the treadmill speed) even 25mph would make the plane move forwards as the plain is being propelled thru the air not via the ground...

Obviously a 747 for instance takes off at around 180mph, so crank your treadmill upto 500mph if you like and use standard takeoff procedure and that's that...

[Viper]

Right, after almost an hour on the phone, me and Craig have come to an agreement on this.

The issue with the opinions on this point is that the original question itself is flawed. It states no reference point for the speed to be judged from, so my opinion has been based on my assumption of the reference point and Craig's opinion is based on his own (retarded) reference point for the speed.

Until the original question clarifies a reference point there is no way a conclusion can be made.

[craig180]

I thoroughly enjoyed hearing Viper tell me I was right as I'm the only person that has referenced a fixed point :A:

Night all x

[matt_vtr_15a]

In reference to this thread Craig is semi retarded...

[craig180]

In reference to this thread Craig is semi retarded...

*with reference.... ;)

Retard.

[Viper]

I thoroughly enjoyed hearing Viper tell me I was right as I'm the only person that has referenced a fixed point :A:

Night all x

We agreed that based on our own assumptions we are both right.

I await a more intellectual OP to pose a fully thought out sentence which eradicates the possibility of assumptions.

[blackie_2k5]

see post 113

Craig argued his case from the start

but did not back up his arguement....


given what the op states, everyone else is correct...... given a true arguement things will change..you need a constant as i mentioned ;)

[matt_vtr_15a]

*with reference.... ;)

Retard.

That was a test, you're just mildly retarded..

[craig180]

We agreed that based on our own assumptions we are both right.

I await a more intellectual OP to pose a fully thought out sentence which eradicates the possibility of assumptions.

Like all my previous posts where I referred only the the 2 variables in the original post?

[craig180]

That was a test, you're just mildly retarded..

That was a test. You're just mildly retarded.

Two sentences or use a semi colon for future reference. ;)

Retard.

[Viper]

Like all my previous posts where I referred only the the 2 variables in the original post?

Then you assumed your own retarded point to judge those two variables from.

[matt_vtr_15a]

That was a test. You're just mildly retarded.

Two sentences or use a semi colon for future reference. ;)

Retard.

Physics retard.

[craig180]

Then you assumed your own retarded point to judge those two variables from.

I used only the facts as explained on the phone ;)

[craig180]

Physics retard.

*A level physics retard.

[titchster]

I can't even be arsed reading the 4 pages that have popped up since I last looked at this.


But, just a little point, if a plane's trying to take off. It's usually at full throttle... That should be a given, no? Regardless of whether the runway beneath it is moving, not moving, uphill, downhill, wet, dry, cold, a little bit warm, a road, a train line, a beach etc etc, any plane trying to take off, is usually at full throttle.

[craig180]

I can't even be arsed reading the 4 pages that have popped up since I last looked at this.


But, just a little point, if a plane's trying to take off. It's usually at full throttle... That should be a given, no? Regardless of whether the runway beneath it is moving, not moving, uphill, downhill, wet, dry, cold, a little bit warm, a road, a train line, a beach etc etc, any plane trying to take off, is usually at full throttle.

You can't use full throttle if you're trying to maintain a set speed, unless of course the belt is accelerating at exactly the same rate.....

[Mochachino]

You can't use full throttle if you're trying to maintain a set speed, unless of course the belt is accelerating at exactly the same rate.....

erm..... :S are you trolling?

[saxo-parts]

At last..somebody else who understands basic aerodynamic principles! Canna beat a twin shaft, high flow bypass pegasus turbofan ;)

should do matey, though most of the planes i worked on are in the history books now lol

[titchster]

You can't use full throttle if you're trying to maintain a set speed, unless of course the belt is accelerating at exactly the same rate.....

That's what I thought was the idea. At no point does it say the plane's doing a set speed, simply that the 'runway' would match the plane's speed...