logic question

R

RIK

Guest
got this from another forum and it turned out a verry good read ..lol

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

Can the plane take off?

Discuss...
 
No, as there needs to be a flow of air above and below the wings to create lift in order for it to take off.

Look at a rolling road, they use fans to simulate the air flow while cars on them, similar idea here.
 
btw i do know the answer....

its got interesting allready haha

its nothing like a rolling road because the wheels arent attached to the engine on a plane :)
 
as an aerospace student id have to agree and say no, but if you really want to get silly if the conveyor belt was travelling the opposite way to what you imagine and the aircraft had reverse thrust enabled on the engines the aircraft could be reversing to stay on the conveyor then release the clamshells (often used for reverse thrust) to start the aircraft moving forward and also be propelled by the conveyor!:laugh: (damn) but what if the a/c had full takeoff weight? the coneyor could be enough to stop it taking off! i knew i shoulda been a car mechanic instead!
 
but the only reasons planes have wheels is to reduce friction when taking off and to land wihout damage

the wheels and the conveyer dont matter,the plane will take off still

the plane isnt driven by the wheels its driven by the engines
 
Yeah the plane is DRIVEN by its engines but LIFTED by its wings...


So I agree with the others, can't fly without moving, unless its a harrier jump jet :glance:
 
Turtle said:
Yeah the plane is DRIVEN by its engines but LIFTED by its wings...


So I agree with the others, can't fly without moving, unless its a harrier jump jet :glance:
Click to expand...

but the engines would still push the plane down the conveyer,,creating air flow over/under the wings
 
Nah, the plane will travel on the conveyor absolutly fine, they could infact get silly speeds... but the plane will NEVER get off the ground.
There is ZERO airflow running through the wings of the plane...

If you had a conveyer and a plane running on it full pelt... if the conveyer suddenly came to a controlled stop it would reduce the length of the runway needed however...
 
Dusk said:
Nah, the plane will travel on the conveyor absolutly fine, they could infact get silly speeds... but the plane will NEVER get off the ground.
There is ZERO airflow running through the wings of the plane...
Click to expand...

the plane moves..so it creates air flow needed to take off.

if the plane had roller balls instead of wheels and the conveyer went sideways.the balls turn sideways but the planne in the direction of the thrust from the engines
 
If you rode your car onto a conveyor belt, then kept a steady 60mph as the conveyor was doing 60 also, you would be completely stationary...

If you then got out the sunroof - and let go of a paper plane, it wouldnt fly at 60mph - it would fall on the floor.
 
bombz4 said:
nah he is right it would be like free wheeling down a hill in a car if the hill was a conveyor!
Click to expand...

yeh it would.and if you stick your hand out you would feel air flow

Dusk said:
If you rode your car onto a conveyor belt, then kept a steady 60mph as the conveyor was doing 60 also, you would be completely stationary...

If you then got out the sunroof - and let go of a paper plane, it wouldnt fly at 60mph - it would fall on the floor.
Click to expand...

cars have driveshafts..planes dont
 
Rik, i was giving the example of the car to simulate the planes position.. it may be traveling at 60mph but only as far as the conveyorbelt is conserned.. to the rest of the world it wouldnt. Driveshafts dont have anything to do with it...

Its hard to try to explain - but if you look down out of the sky via gps.. you would see a stationary plane (the travelator would go about 100mph and the plane would be countering the resistance of the travelator by traveling the equal 100mph) however although the plane does have potential energy it hasnt got any *real* kinetic energy to anything outside the travelator. This means that if you stood next to this plane at the side of the travelator, the plane would be roaring at 100mph (which all of the 100mph is being absorbed by the travelator - because the plane isnt actually moving...) but it will be exactly where you are..
The plane has no air resistance as it is not actually traveling... just like you wouldnt have any air resistance... you as a person have more chance of taking off - as a plane in the same situation :D
 
In terms of physics yes it would take off. In terms of reality and technology NO it wouldnt. Because there are safety features built into the aircrafts that would detect that the wheels are running in the opposite direction to which the turbines are trying to propel the aircraft.

Wat iv always wanted to know is, why at night when your landing do they want you to close your wee plastic blind thingie??

Daz :alien:
 
RIK said:
its nothing like a rolling road because the wheels arent attached to the engine on a plane :)
Click to expand...

I gave the rolling road as an example as they sit fans at the front to simulate air flow as if the car was actually moving. In both cases, despite engines being run, the objects are static.

Think if your on a treadmill. Your running on that, you don't feel a wind resistance like you would if you were actually out running, say along the road.

The plane requires this resistance to create lift and take off.
 
No it wouldn't take off as there is no airflow across the wings to provide lift which is what an aircraft requires to fly, the plane would be standing still in relation to the Earth and therefore its atmosphere because the conveyor would be matching its speed in the opposite direction cancelling out the thrust from its engines.
 
YES it would!! The wheels are free rolling! the belt doesnt make a hoot of a difference! Think logically! If ur standin on a converyor belt and running the opposite direction then you would stand in the same position, but the plane is not moving by the driving force of the wheels but of the turbines thus making it "free wheel" along the conveyor belt!! God damn!
 
unless my original theosis is incorrect i will agree with k10daz however i stand by the fact that no it wont coz its standing still ...goddamit rik tell ius
 
rlees85 said:
but still doesnt it need air resistance to lift off?
Click to expand...

It will get it as it will move!!! it wont stand still the turbines will propel it along the conveyor and the wheels wont make a difference as they are not part of the drivetrain so to speak!
 
it doesnt matter if the wheels are free rolling. The engines are pushing the plane forward and therefore rolling on its wheels the conveyor belt would detect watever the speed the wheels are turning then the conveyor belt will do the same and therefore you would be stationary. it dont matter if the wheels are free rolling or not.
 
what effing differerence does it make how fast or slow the wheels are going? they dont make a difference!
 
K10Daz said:
It will get it as it will move!!! it wont stand still the turbines will propel it along the conveyor and the wheels wont make a difference as they are not part of the drivetrain so to speak!
Click to expand...

how will it be propelled along the conveyor belt as the plane is pushed by turbines and will in turn roll on its wheels. the conveyer belt detects this speed and matches it. so you wouldnt go anywhere.

its like if you are on some roller skates with a fan attached to your back. if that fan pushes you along at say 1 m/s and you are on a conveyer thats travelling the opposite way at 1 m/s your not going anyway. the method of propulsion is irrelevant as long as the conveyer and the plane speed are exactly the same but travelling in opposite directions you wont go anywhere. which it will be as he said the conveyer detects the the planes speed and matches it but in the oppsite direction.

therefore no forward movement, no lift.
 
actually iv just drawn it out and it would NOT take off lol - sorry guys! The wheels would need to be rolling in the same direction as the aircraft for it to move as the belt would create resistance hehe. Silly me, i do apologise
 
Right, a have just sat with my thinking cap on and a cup of tea, i have scientifically worked this out and it will not take off. All be it the fact the plane is not actually moving due to the fact the conveyer belt is countering the speed of the plane but the fact that Rik quite blatingly wrote......
a plane is standing on a runway


therefore my conclusion is no it wont take off and i deserve one gold medal
 
the answer is NO...

if you just think about what is required for the actual plane to take off you'll realise that by adding a conveyer belt that exactly matches the speed at which the wheels move at it will not only never take off but wont move in a fwd direction...

the only way would be if the plane were to take off like a harrier...

you really do have to take trajectory into consideration...

and use formulas: f=mXa, Mm= mXv, etc...
 
the answer is YES!!!!

the jet engines will push the plane forwards because the engines are pushing against air.

the plane would take off just like normal only the wheels would be turning twice as fast.

imagine you are on a tread mill and you hold on to a jet engine the jet engine will pull you off the tread mill.
 
Nice one Nex I reckon you're right after reading the first post properly, the plane and conveyor are travelling opposite directions, making the wheels turn twice their normal speed but the plane would still have forward motion at its normal speed.
 
the engines will be trying to move the plane forward, the wheels going backwards - tell us how it will take off then? How will the plane move forward?

look at me - totally changing my view on it, but im not well at the moment - took some antibiotics and pain relief an got my thinking hat on just like ben!

sonic said:
Nice one Nex I reckon you're right after reading the first post properly, the plane and conveyor are travelling opposite directions, making the wheels turn twice their normal speed but the plane would still have forward motion at its normal speed.
Click to expand...


The wheels need to be going forward for the plane to take off - they cant go backwards whilst the aircraft is going forwards - go get a toy car and try it! It doesnt work, cant work, wont work

end of
 
First I thought it would, then I thought it wouldn't, now I'm almost sure that it would. Think of those horizontal travelling escalator things, if you were to walk backwards on them you do feel air resistance. The wheels would also be moving exactly the same way that they would if the plane was taking off normally, as if you think about it its bascially going the same direction it would anyways. I think it would. :)

Or would you feel air resistance lol. :s Hmm, I'm not so sure again now lol!!!
 
Im confused now, think i need more medication! Im gonna email Jeremy"im not curly"Clarkson and see what he says!
 
rik put us out our misery! personally i dont think it will as if its running on the spot, there is no air resistance for it to lift
 
This has really got me thinking now!!! In comparison to the conveyor belt thing its speed will be whatever the plane is going doubled as it is travelling on the opposite direction. Therefore there will be a force pushing backwards on the plane, but an equal force pushing the plane forward which in effect cancels it out, providing no resistance. Ok, I will stop thinking out loud now, I think it won't take off lol. :) A-Level Maths and Physics coming into play there, still not sure though!!!
 
the egg. the 1st chicken would have come from this egg. the birds that mated to make this egg were not chickens, but something very similar but not quite chicken.
 
K10Daz said:
the engines will be trying to move the plane forward, the wheels going backwards - tell us how it will take off then? How will the plane move forward?
look at me - totally changing my view on it, but im not well at the moment - took some antibiotics and pain relief an got my thinking hat on just like ben!
The wheels need to be going forward for the plane to take off - they cant go backwards whilst the aircraft is going forwards - go get a toy car and try it! It doesnt work, cant work, wont work end of
Click to expand...

I don't know Daz I'm confused, it seems simple but I can't get my head round it, my lounge is covered in drawings of planes on conveyors, other forums have had threads dozens of pages long on this one, Email Braniac see if they can help, Rik you're a git for this one, my head hurts.:confused: :confused: :confused:
 
it would take off...the conveyer and the wheels are a red herring if you like.

the plane would still travel from one end of the conveyer to the other the wheels could move backwars sideways are whatever the plane would still travel down the runway

here is a reason that was given in the thread got it from

Reason: The wheels act independently of the forward motion of the plane, they're not driven by or connected to the engine. The plane doesn't "drive" the wheels to build up speed, they just rotate as a consequence of the friction between the rubber and tarmac.

The forward thrust of the engines can't be affected by the conveyor, only the wheels are. So basically the plane would "move" forwards even if the wheels were rotating backwards.

It wouldn't matter if the plane was on wheels, or skis, or even on its belly (although friction would increase and more engine thrust would be required to overcome it) - the plane would still move forwards.

It's a bit of a red herring question - the conveyor moves faster proportionate to the speed of the plane - which would simply mean the wheels would go backwards faster and faster, but because the wheels aren't physically connected to the "engine" like a car or bicycle is - it wouldn't make any discernable difference to the speed of the plane.

and another good answer...

A supermarine spitfire(the old sea plane ones) is floating on the water. As it accelerates, the current of the water speeds up. Eventually, at say 60mph, the plane takes off and the water current is 60mph in the other way. The floats would be pushing against the water at the combined speed of 120mph.
 
not going to read 5 pages as i know the answer!! it will take off the plane is not driven by its wheels!! there free rolling!!! the engines thrust will push the plane forward regardles of the conveyer belt undernieth the wheels will just spin faster to compensate for the conveyerbelt going in the oposite direction.. if it was acar with wings it would be different as the cars wheels give the car momentem.. think about it..
 
im still adament that it wont, how can the plane travel along the cnveyor belt if the belt matches the speed of the wheels. the speed the wheels are turning is directly proportionate to the speed the plane is traveling. for example if the plane accelerates becuase of the thrust of the engine, the friction between the road and the rubber on the wheels would turn the wheels. if the conveyor belt matches the speed of the wheels then it will in turn match the speed of the plane if they are both proportionate. therefore the plane cannot travel forward and cannot get any wind resistance. i KNOW that the plane will not take off.
 

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