Are you an idiot?

[Robert]

I like asking this question.



An airplane is sitting on a conveyor belt. This conveyor belt is programmed to match the exact speed the the airplane is traveling in reverse. If the plane is traveling forward, the conveyor belt is running backwards at the same speed.

Will the airplane be able to take off?

[Squirrel]

No, 'cause there won't be any air moving around the wings, and therefore no lift.

I hope I didn't just make a terrible arse out of myself.

[AstrayCliche]

That's what made me hesitate for responding first, but I say the same.

[XXX]

the correct term is
general boardon
a convenient shortening of General - Board - Moron
if the poll turns out the way it should it will end up with 66 % yes
32 % no
1 % ggahh..mghuuhhh

slightly behind adeline's moron ratio of
64 % yes
33 % no
3 % nevermind that, where are elliott's lost briefs?


i've done the math,
complicated algorithms and such,
you can take my figures as gospel.
worship them... please. carl sagan would approve.

[vaya con dios]

long hair

[Exterior Muffinz]

I vote yes.

The thrust of the jet/propeller is relative to the air around it, not to the ground below. Now if the headwinds were equal to the forward thrust of the engine ...that would be another story. In fact, there's an aircraft called the Fieseler Storch that can fly in reverse at walking pace with sufficient headwinds.

[Squirrel]

So what happens when it takes off from the conveyor belt, kicking off enough thrust to move it forward at whatever terrible speed it should be already at? Ouch. D:

[Exterior Muffinz]

The aircraft wouldn't go shooting off.

[Jackal]

I cheated and saw Squirrel's answer before I had time to think. I would have said no, because when I walk on a treadmill I can't fly. ;)

[Mary Alice]

I would think the jet could still go off - lord I hope I'm not a moron.

[Drevpile]

no

[Exterior Muffinz]

A conveyor belt going 100mph does not cancel out a plane moving at an airspeed of 100mph.

You're idiots! :scared:

[El Loto]

The plane is sitting ON the conveyor belt. It has no airspeed.

[i]

I'm quoting Iggy.

Yeah the wheels don't do anything except support the plane. The thrust from the jet engines is relative to the air. So I voted yes.

[i]

The aircraft wouldn't go shooting off.

yeah, the wheels would just be spinning really fast.

airplanes don't rely on wheel-to-ground traction/friction to take off, unlike cars/bikes/etc.

[Jackal]

The jet engine just propels it forward, it needs wind to raise up. Otherwise planes wouldn't need wings. We could take rockets to places!!! But rockets fly without wings. Well, they are going up and not being driven or landed and they are really, REALLY fast. :bear:

[Nak Nak]

The plane is VTOL equipped, making the question irrelevant.

[Hi There, Am Pam]

The answer is yes. The plane is actually a helicopter. It's a trick question.

[Foxing Peculiar]

Aye. The jet/prop creates thrust relative to the surrounding air, not to the ground -- if the ground is matching the speed in reverse, that just means the wheels are spinning twice as fast -- which would be irrelevant, since they're not tied to the propulsion of the plane. In any case, it's the forward thrust that moves air over the wings and lifts the plane.

There might be a little added friction to deal with from the wheels rotating at that speed, but not enough to screw with the takeoff, I wouldn't think.

Unless there's a guy on the plane with a bomb who blows it up before this all happens. That might be the answer.

[Fab]

I really can't think now, am well confused. I was starting to side with Iggy, as you'd still be getting air sucked through the engines,but it wouldn't really be moving past the wings enough to cause lift.

[Foxing Peculiar]

I really can't think now, am well confused. I was starting to side with Iggy, as you'd still be getting air sucked through the engines,but it wouldn't really be moving past the wings enough to cause lift.

Ah, but why not?

The ground is moving, but the movement of the air is no different from normal circumstances. Nothing in the question says the plane is staying in one place -- the only thing the conveyor belt affects is the speed at which the wheels rotate, but that has nothing to do with propulsion, since the propulsion relies on the air, not the ground.

[Herr Lipp]

No. The question of air suction is irrelevant (that's what jet engines do!). Planes need to suck in that air, to start forward motion (through the wheels) to get to like 180mph when the airflow over teh top of the wings is substantial enough to make teh nose lift.

If the treadmill is going backwards at 180mph, and you're only putting in enough thrust to roll forward at 180mph, then in theory the plane wont move an inch, it'll just make a lot of noise.

[Herr Lipp]

since the propulsion relies on the air, not the ground.

I disagree. If that were true, why would you need runways? If you can't reach the critical landspeed for the air to move fast enough over the wings, you're fucked.

PWNED.

[Foxing Peculiar]

Okay, let me rephrase -- the propulsion relies on the air, not the WHEELS.

In response to your first post, it's not exclusively about thrust, either -- it's about motion; look at the wording of the question. If the plane stays in one place, the conveyor belt doesn't move either. Which means the plane is already in forward motion and can achieve the landspeed necessary relative to the air at ground level -- the conveyor belt just doubles the work the wheels have to do (but the wheels aren't what's moving it, which is why it still moves forward).

[Mary Alice]

my dad is a pilot and I don't know this... :( I still think it would go off but y'all from the other side are giving decent arguments about it needing lift, and I'm not 100% confident in my answer. You know this would be the kind of question they SHOULD ask on some gameshow like "who wants to be a millionaire" - that would make a good game show.

[Herr Lipp]

Yar I know it relies on air, but you need to get the big lump of metal cruising very fast to get enough air to make that shit fly. Before you can do that you need the wheels going tres rapide. And if this magic conveyor belt can match the wheel speed I dont see how you can get the wings moving forward??

You won't change my mind, but please feel free to explain your point further.

I like this thread.

[Foxing Peculiar]

Yar I know it relies on air, but you need to get the big lump of metal cruising very fast to get enough air to make that shit fly. Before you can do that you need the wheels going tres rapide. And if this magic conveyor belt can match the wheel speed I dont see how you can get the wings moving forward??

You won't change my mind, but please feel free to explain your point further.

I like this thread.

Okay.

You've got four things in play here: -- the wheels of the plane, the plane's engine, the air around the plane and the conveyor belt.

When the scenario starts, nothing is moving.

The plane's engine fires up. This pushes on the air around the plane and creates, say, 100mph of forward thrust. Without the conveyor belt, this pushes the plane forward at 100mph and therefore rotates the wheels at 100mph.

In this scenario, the plane generates 100mph of thrust against the still air with the engine. This still pushes against the air (which remains still) and causes the plane to move 100mph forward. The conveyor belt then starts moving 100mph backward, which means the wheels are rotating at 200mph forward. However, the entire plane is still moving at 100mph, because the air is still not moving at all.

Even when the plane's on the ground, its only using the ground for support, not to generate speed. Unless the conveyor belt can move the surrounding air, it won't affect the plane's forward motion.

[Foxing Peculiar]

you need the wheels going tres rapide.

Not so. You just need the plane moving to get air moving around the wings -- the wheels are incidental to that.

The conveyor belt would only matter if the wheels were what provided the forward thrust for the plane. Because they're not, the belt is irrelevant to whether or not the plane will move forward or not.

[Fab]

Nothing in the question says the plane is staying in one place

This conveyor belt is programmed to match the exact speed the the airplane is traveling in reverse. If the plane is traveling forward, the conveyor belt is running backwards at the same speed.
Therefore the plane isn't moving in relation to the ground, and the only air moving past the wings would be wind.

[Foxing Peculiar]

Therefore the plane isn't moving in relation to the ground, and the only air moving past the wings would be wind.

Okay, I think I see what the issue is here.

You have to consider how the situation starts -- at the beginning, nothing is moving, right? Then the engines of the plane fire against the air and the plane starts moving forward. Even if the conveyor belt begins moving backwards at the same time, because everything was initially still, the initial forward motion of the plane is relative to that state, and it won't get canceled out by the backwards motion of the belt.

I dunno. I can see this in my head, but I know I'm not explaining it right.

[Fab]

The plane's engine fires up. This pushes on the air around the plane and creates, say, 100mph of forward thrust. Without the conveyor belt, this pushes the plane forward at 100mph and therefore rotates the wheels at 100mph.

In this scenario, the plane generates 100mph of thrust against the still air with the engine. This still pushes against the air (which remains still) and causes the plane to move 100mph forward. The conveyor belt then starts moving 100mph backward, which means the wheels are rotating at 200mph forward. However, the entire plane is still moving at 100mph, because the air is still not moving at all.
um, you've gotten confused somewhere, sod it being a plane for a sec and pretend it's a car:

car accelerates to 30mph
conveyor belt is now moving 30mph in the opposite direction
the car's wheels are now moving at 30mph and relative to the ground it is 0mph, no part of it is moving at 60mph

[Foxing Peculiar]

car accelerates to 30mph
conveyor belt is now moving 30mph in the opposite direction
the car's wheels are now moving at 30mph and relative to the ground it is 0mph, no part of it is moving at 60mph

Right, but you can't compare it to a car, cos a car's propulsion comes from its wheels, a plane's doesn't. So for a car, yeah, that's what would happen.

But imagine it like a toy car (where the propulsion comes from, say, a kid's hand instead of the wheels). If the kid is moving forward the car is going to move forward, even if the belt is moving directly counter to the kid's movement -- the only thing that changes is the rotation of the wheels, but the rotation of the wheels isn't what determines the car's speed, the kid does.

In this case, the kid is the engine pushing against the air.

[Fab]

The situations don't compare unless the kid is on the conveyor belt with the car as that's where the plane's propulsion is coming from (by which I mean it is all contained on they conveyor belt). If the kid is on the conveyor belt then clearly he will stay in the same relative airspace with the car.

[Foxing Peculiar]

But the air isn't contained on the conveyor belt -- the conveyor belt only moves the ground not the air around the plane. The only thing that creates drag is the friction between the wheels of the plane and the ground -- but with the initial thrust, you've already overcome that friction, so it doesn't matter what the ground is doing -- the air and plane are both independent from it already.

[Fab]

But the propulsion is caused by the engines sucking air through them, this is all self contained.

[Foxing Peculiar]

The first part is true, but I'm not sure what you mean by the second bit.

[Herr Lipp]

The engines are providing the forward motion, that's a given, but this is transferred through to the wheels for such time as the plane reaches a speed (I have 180mph in my head for some reason) whereby the wings take over and the wheels become redundant.

If the plane isn't moving, which it wouldn't if the treadmill could match it perfectly, flight would be impossible. Air isn't important until you leave the ground, and with this conveyor belt it's not possible to get to that point.

[Herr Lipp]

TO go back to the wording of the question, the conveyor belt can match teh exact SPEED of the plane. There isn't a complicated formula to flight, a winged object must simply reach and maintain a certain speed (it needs to do this with it's wheels) to obtain flight. If it's unable to reach this speed then there will never be enough air travelling over the wings to get lift

The engines aren't what makes something fly, it's the aerodynamics. Engines just keep the air going over the wings.

[Foxing Peculiar]

If the plane isn't moving, which it wouldn't if the treadmill could match it perfectly, flight would be impossible. Air isn't important until you leave the ground, and with this conveyor belt it's not possible to get to that point.

The plane IS moving, though, and the only reason movement relative to the ground is important is BECAUSE of movement relative to air -- you have to get enough air moving over the wings to generate lift. It has nothing to do with the wheels -- they're freewheeling.

If the wheels start turning at all, the plane will move forward, regardless of what the belt is doing -- the belt could be moving in reverse at 10x the speed of the plane, and the plane would still move forward. It's all about overcoming the friction caused by the weight of the plane -- and no belt is going to generate enough.

[Foxing Peculiar]

TO go back to the wording of the question, the conveyor belt can match teh exact SPEED of the plane. There isn't a complicated formula to flight, a winged object must simply reach and maintain a certain speed (it needs to do this with it's wheels) to obtain flight. If it's unable to reach this speed then there will never be enough air travelling over the wings to get lift

The engines aren't what makes something fly, it's the aerodynamics. Engines just keep the air going over the wings.

Right -- that speed is relative to air, not what the wheels are touching. If the plane is moving relative to the air, which it would be, then it'll fly.

[Herr Lipp]

ack, let's not get in to friction. I appreciate your point. But i;m operating theoretically, within the confines of the question, that it'd be possible for a treadmill to support an aircraft and, as stated, move the aircraft's wheels backwards exactly as fast as the engines can move it forward.

[Foxing Peculiar]

Friction's kind of at the heart of it, though ;)

And again, the answer's in the question there -- the wheels AREN'T moving the plane forward -- they just support the plane as it moves forward. So yeah, the treadmill could match the plane's speed, but not prevent its motion.

[i]

The engines are providing the forward motion, that's a given, but this is transferred through to the wheels for such time as the plane reaches a speed (I have 180mph in my head for some reason) whereby the wings take over and the wheels become redundant.

Okay c'mon, think about those little wheels of a jet aircraft relative to their size of their load. There is no transferring of motion through those. The only time that happens is when you're being taxied around the runways before takeoff and after landing, and even then there are aircraft tow tractors to help.

Alex, Iggy and MA are right, y'all. It's not like the DeLorean out of Back to the Future. You're thinking of a plane as a car with wings.

[Exterior Muffinz]

Word.

Plane wheels are free-spinning.

Myth busted.

[Herr Lipp]

You really believe that when the plane is streaming down the runway, the wheels are just spinning around at their own leisure?

Of course the fucking wheels are moving the plane forward, lol. How far do you think it would get with no wheels? The engines push air through the back of themselves, while the plane is taking off this is mostly through the wheels, and as it approaches the moment of take off it is shifting more and more to the wings.

To suggest that a plane is able to take off, without gaining any forward motion is moronic. And since the wheels provide the initial forward motion, and the conveyor belt is stopping that motion then you're fucked! The engines could be pushing the air out at 500mph but if the wheels never got spinning in the first place it wouldnt matter. The whole conveyor belt system takes away airflow over the wings. Case closed.

Friction isn't mentioned in the question, so no, it isn't the whole point. Even with friction, this magical conveyor belt would no doubt compensate for it.

Ahhhh why dont you all just die slowly.

[Kelly Kapowski]

what the hale

[Exterior Muffinz]

:wtf:

[i]

You really believe that when the plane is streaming down the runway, the wheels are just spinning around at their own leisure?

Of course the fucking wheels are moving the plane forward, lol. How far do you think it would get with no wheels? The engines push air through the back of themselves, while the plane is taking off this is mostly through the wheels, and as it approaches the moment of take off it is shifting more and more to the wings.

To suggest that a plane is able to take off, without gaining any forward motion is moronic. And since the wheels provide the initial forward motion, and the conveyor belt is stopping that motion then you're fucked! The engines could be pushing the air out at 500mph but if the wheels never got spinning in the first place it wouldnt matter. The whole conveyor belt system takes away airflow over the wings. Case closed.

Friction isn't mentioned in the question, so no, it isn't the whole point. Even with friction, this magical conveyor belt would no doubt compensate for it.

Ahhhh why dont you all just die slowly.

wtf/hale indeed. look, i'll spoil it for everyone and just post this so we can end this:

GOOGLE it. airplane treadmill. the answer is yes, it takes off. there are ways that the question can be misinterpreted because it is essentially a physics question and not a brainteaser or logic problem, and that always causes a lot of debate.

[Kelly Kapowski]

well i think it's quite unfair to suggest someone is an idiot because they get the answer wrong. Sorry if God left the physics bulge out of my brain!

That being said, i didn't try to understand but i'm 98% sure i wouldn't have anyway if i even tried. And i feel no shame, thanks V. much!!1

[i]

Yep, it is quite unfair to suggest that. That's why I said it is basically a physics question and that's why I posted the answer so no one feels stupid about it.

There's also a number of youtube videos attempting to demonstrate it in action.

[Kelly Kapowski]

will for blamo prez :cry:

[Jackal]

I'll believe it when I see the Youtube video.

[Dovecoat]

The plane wouldn't have a lack of motion. It just wouldn't be moving. You see?

If the conveyer is going 200 mph in reverse, and the plane is going 200 mph forward... how fast is that plane going? You see, if it wasn't moving, then it wouldn't stay stationary... the conveyer would move it backwards. But since the plane is moving, too, it stays put.

Now, engines... Plane engines involve combustion. Or at least they have for the past 100 years or so. Therefore, yes, air goes through the engines, propells the plane, etc, etc, etc... However, the engines are turned on, which causes the air to move through the them. The air moving through them isn't what causes the engines to turn on.

So... on a conveyer belt, you have a seemingly stationary plane (that's actually going 200mph) with working engines... of course it takes off!!!

Note: I haven't read the entire thread. Sorry if this is redundant.

[El Loto]

I hate this thread. My brain is asking me if it can explode.

[Dovecoat]

I hate this thread. My brain is asking me if it can explode.

A: Yes.

[xangeleso]

will it take off? sure
Will it fly? I sure as heck don't know!

:xo: Stef

[Exterior Muffinz]

Sorry folks, but it's not that hard to figure out.

Landing gear wheels = free-wheeling
Forward momentum = thrust against surrounding air
Treadmill = no effect (bar bearing friction)

[Robert]

The engines aren't what makes something fly, it's the aerodynamics. Engines just keep the air going over the wings.


Does a helicopter have to already be moving up to generate enough thrust to leave the ground?

[DrHibbert]

Huh. Interesting thread. I read the whole thing and would never have expected to enjoy nerdy science stuff (though I comprehended none) (and yes, I realize that this alone makes me an idiot).

I voted no, and I'm sticking to it. I'm with Fraser! The youtube videos mean nothing! Yay for idiots!:D

(PS Pls link the youtubes)

[Chopstick]

Plane speed: 100 mph
Treadmill speed: 100 mph
Wheel speed: 200 mph

The plane will still move forward at 100 mph. The idea that it would appear to be stationary is kinda crazy. It's even crazier if you think it would appear stationary, and then still take off.

[Dovecoat]

^ huh... good point.

*slaps forehead*

[DrHibbert]

There's also a number of youtube videos attempting to demonstrate it in action.

Damn it, I can't find them! My mind cannot fathom an airplane successfully taking off and flying away in this scenario.

[Squirrel]

I was asking people at work about this, and someone came up with (what I thought was) a good point - wouldn't the plane begin taking off front-first (IE the front wheels lift off the ground before the back ones) and then just be pulled back by the conveyor belt to squash itself like the proverbial hedgehog?

[Peter]

No, the plane will not take off. If the conveyor belt is moving backward at the same rate as the plane is moving forward, then the plane will remain stationary. In order for a plane to take off, it must move through space in a forward motion and cause air to travel around it's wings. If the plane is stationary, there will be no air movement over the wings to give it lift.

The plane won't fly!

Unless it's a harrier jet.

[Robert]

Incase you guys were wondering, the plane would take off.

Airplane engines move air. Duh.

But air they moves affects all surfaces of the wings. Generating lift.

[Exterior Muffinz]

I can't understand why people think the belt cancels out the forward momentum.

The forward thrust from the prop/jet is pushing against air, which propels the engine -and everything that's attached to it- forward. The wheels have no say in this equation at all because they're free spinning. I can't spell it out any clearer. The belt has no effect on the plane.

[Robert]

Well, it is a question desgined to trick people.

[i]

No, the plane will not take off. If the conveyor belt is moving backward at the same rate as the plane is moving forward, then the plane will remain stationary.

The plane would actually move forward because the wheels are free spinning. The engines push AIR, and this causes the plane to move forward. The wheels would just spin twice as fast as usual because of the conveyor belt. (See Chopstick's post.)

The belt only affects the wheels. Not the air, not the plane.

I was asking people at work about this, and someone came up with (what I thought was) a good point - wouldn't the plane begin taking off front-first (IE the front wheels lift off the ground before the back ones) and then just be pulled back by the conveyor belt to squash itself like the proverbial hedgehog?

Don't the front wheels always lift off the ground before the back ones? I don't get it.

[i]

Note: There are newer planes to be fitted with electric motors on their undercarriage used to move them. Delta's new 737s apparently will be using one system similar to the following.

http://www.drives.co.uk/news/technews/news_technews372.htm

But that's an aside: if you read the article you'll see it's clear that modern aircraft can only move using jet engine thrust or by being towed. How does the plane get out and get into the gate so precisely? Towing. How does the plane move around the runways? Jet engine thrust (not as precise control).

The only thing I don't understand is how people are so adamant that it can't take off AFTER it's already been explained. It's not like a car. Planes move relative to the air. A conveyor belt does not move the air (significantly).

[Mary Alice]

in answer to Mark's co-worker's question

wouldn't the great power of the jets moving forward be so much stronger than whatever little force pulling back from the treadmill?

[Squirrel]

Wait.... I am pretty drunk now and I think I understand the counter-point to all my arguments. I will wait until tomorrow to re-establish my thoughts, but I think I see the big picture. Man.

[Chopstick]

...had what alcoholics refer to as "a moment of clarity."

[Cool As Ice Cream]

i have no idea what a conveyor belt is.

i voted no, as an answer to the thread title.

[Chopstick]

i have no idea what a conveyor belt is.

i voted no, as an answer to the thread title.

Aeroplane sized...
http://www.automation-supplies.com/resources/_wsb_318x275_0704+Low+profile+conveyor+with+2+belts.jpg

[jas1n]

no airplane, yes i am an idiot.

[Cool As Ice Cream]

Aeroplane sized...
http://www.automation-supplies.com/resources/_wsb_318x275_0704+Low+profile+conveyor+with+2+belts.jpg

ah, i see. :)

in that case, i think it has no effect whatsoever on the plane taking off.

edit: so i should have voted yes.
now i'm an idiot.

[i]

it has an effect on the plane's wheels and the friction / heat of the wheel bearings :D

[Chopstick]

I put the question to my two roommates and both of them got it wrong. It was such a pleasure to watch their minds snap after I told them the correct answer.

[Robert]

it has an effect on the plane's wheels and the friction / heat of the wheel bearings :D

Not a great one though.

Airplane wheels are pretty facking tough.

[i]

yeah. but still a slight effect more than no effect whatsoever

[Cool As Ice Cream]

how about this question:
if you put a marble in a tube that is formed like a circle and give it some speed, what route will it choose when it leaves the tube?

will it keep moving similar to the way it did in the tube and follow route A, will it try to escape the form of the tube and move outwards (route C), or will it follow a straight line (route B)?

the added picture is just an illustration, not a scientific drawing of the exact route(s).

[Foxing Peculiar]

how about this question:
if you put a marble in a tube that is formed like a circle and give it some speed, what route will it choose when it leaves the tube?

will it keep moving similar to the way it did in the tube and follow route A, will it try to escape the form of the tube and move outwards (route C), or will it follow a straight line (route B)?

the added picture is just an illustration, not a scientific drawing of the exact route(s).

Route C, I think. My logic being that the momentum you give it combined with the curved shape of the tube means the force affecting the marble is pressing on the outside edge of the tube, so once that tube gives way, the centrifugal force will throw it out, rather than continuing the curve or just shooting straight out.

Though that's just a guess.

[brainiac]

If you're not counting gravity's effect, then I think it'd be route B. It would travel off on a path that's tangent to the circular arc of the tube. But with gravity affecting its path through the air, I'd say it would probably look more like A.

[Cool As Ice Cream]

the tube is placed horizontally. so the direction of gravity is ortogonally(sp?) on this picture and should have no effect on the direction of the marble.

[Squirrel]

Depends which way it's spinning, surely?

[Cool As Ice Cream]

nah.

[Nak Nak]

B. Although maybe A if it wasn't going fast enough. Bram's gonna say this was a trick question or something and I'll feel like a fool for answering.

[i]

I'm going with B as well.

[brainiac]

the tube is placed horizontally. so the direction of gravity is ortogonally(sp?) on this picture and should have no effect on the direction of the marble.

Oh, oops. I was picturing it standing up, with the ball being sort of fired out into the air at the end of the tube.

Yeah, I'd say B.

[Chopstick]

I thought it might veer slightly towards path C because the marble would likely have a clockwise spin as it exits the tube. Without the spin, I think it would go straight down path B.

[Jackal]

B- But I think it depends on the speed of the marble.

[Cool As Ice Cream]

it's just b. the marble has no reason not to follow a straight path.

spin my ass.

[Herr Lipp]

Does a helicopter have to already be moving up to generate enough thrust to leave the ground?

you can't compare a plane with a helicopter, derrrrrrrr brains!

[Kelly Kapowski]

i think B but have nothing to back that with except it was just my instinct.

[Robert]

you can't compare a plane with a helicopter, derrrrrrrr brains!

The concept of flight is the concept of flight.

[Chopstick]

The concept of flight is the concept of flight.

The idea that a plane can take off without its wings moving forward is comparable to a rotary wing aircraft (helicopter) taking off without spinning its rotors. The two can be compared, but it seems you can't do it correctly.

[Robert]

Basically the same thing in a different direction. :/

The concept of flight is the concept of flight.

[Fab]

Oh PS I realised the plane would take off when I couldn't sleep the other day.

And B to Bram's thing.