A jet plane on a large treadmill

[PNWbrit]

Shit! Now I think I'm wavering!

Someone mentioned a sloped runway earlier. What if the conveyor is sloped, the plane will roll down hill, the conveyor cannot stop it no matter how fast it moves.

Am I right? Is the force exerted on the plane by gravity effectively the same as the engines in our original model.

[tonghands]

My Christmas Wishlist:

1) Everyone that posted about rollerblades in this thread would go back and edit it to skateboards, because rollerblades are kinda gay.

2) Several squadrons of low radar cross section, pulse doppler radar equipped, low level fighter/bombers equipped with weapon racks that can carry treadmills to drop on fuckers that come up with threads like these.

3) altaski would change his username to Orville, or possibly Wilbur.

[shmerham]

Does everyone get the feeling that the person that created this riddle knew that the ambiguity of the speed part and the inability to duplicate a perfect control system would create endless discussions like this?

Evil, evil, evil bastard!

[The Suit]

Does everyone get the feeling that the person that created this riddle knew that the ambiguity of the speed part and the inability to duplicate a perfect control system would create endless discussions like this?

Evil, evil, evil bastard!

I think the person who created this riddle knew that lots of people don't think so good.

[The AD]

Does everyone get the feeling that the person that created this riddle knew that the ambiguity of the speed part and the inability to duplicate a perfect control system would create endless discussions like this?

Evil, evil, evil bastard!

I predict an eight year old kid came up with the question and asked his dad the answer. Old dad probably said, "ha ha, that's easy son. The plane won't be able to take off." Then he thought about it for a few more minutes and started scratching his head.

In my (perhaps messed up) head, the treadmill should be able to resist the plane rolling downhill on a sloped runway.

[bagtagley]

1) Everyone that posted about rollerblades in this thread would go back and edit it to skateboards, because rollerblades are kinda gay.

done....

[Out_to_lunch]

If the conveyor is providing equal but opposite movement to what the plane would have if it were on solid non moving ground, the plane, in relation to everything (the ground, air, surroundings) except for the conveyor, isnt going to be going anywhere. The only thing moving is the wheels, and wheels dont make an airplane fly.

Wind moving over and under the wings is what gets airplanes airborne, and because the only thing moving are the wheels, there is no way, with out the help of a massive fan or something like that or extremely high winds, that the plane is going to get off the ground.

I kind of thought this thread was going to have a picture of a plane on a large treadmill. I was kind of dissapointed.

And all in all its kind of pointless. I mean have you ever seen a treadmill big enough for a 747 before?

[Dirty Hoar]

Hey everybody... we landed on the moon!!!

You know, it's a great debate... well, for the most part... but it's been proven time and time again that the 747 will gain speed and fly. So lets look at it a different way.

DRAAAGSTERRRRS ON TREADMILLS... SUNDAY SUNDAY SUNDAY!
Ok, you have two treadmills laid out side by side and each one is 1/4 mile in length. Each treadmill counter acts the speed of the dragsters just like the 747 one. In lane one you have the worlds fastest nitro funny car. In lane two you have a jet powered dragster. Who will win?

[Squatch]

Hey everybody... we landed on the moon!!!

You know, it's a great debate... well, for the most part... but it's been proven time and time again that the 747 will gain speed and fly. So lets look at it a different way.

DRAAAGSTERRRRS ON TREADMILLS... SUNDAY SUNDAY SUNDAY!
Ok, you have two treadmills laid out side by side and each one is 1/4 mile in length. Each treadmill counter acts the speed of the dragsters just like the 747 one. In lane one you have the worlds fastest nitro funny car. In lane two you have a jet powered dragster. Who will win?

But what if there is a hurricane blowing against motion of the jet powered dragster? And what if the hurricane's name is Ditka?


Hall of Fame for sure...this thread has undoubtedly spawned countless signatures, lifelong animosities, and shown us all the danger of a little knowledge and access to an internet forum.

[DINMS]

In all practicality, the plane will take off as normal, only with it's wheels spining at twice the normal speed, anyone who sees otherwise is so patheticly stupid that it's really very very hard to fathom.

Someone said something about a car driving on a trailer at highway speeds, early in this thread, before I lost so many IQ points. The engine would probably die as soon as it hit the trailer.... asuming you didn't simply take your foot off the gas and shift into first.... *rolleyes* Asuming you weren't a 'the plane would not fly person' and took your foot off the gas and coasted onto the trailer, the only forward force would be the momentum of the spinning tires and the engine idling.

Use some common sense people. I realize it's not common anymore, but... well, just fucking make sure you take account all the factors.

[MeatPuppet]

Does everyone get the feeling that the person that created this riddle...

LOL! It's not a riddle. It's a critical thinking exercise, and a simple one at that. The fact that it has caused so many people so many problems(here and other places) is a little disturbing. Our public education system obviously is missing something in it's curriculum.

[MeatPuppet]

I think the person who created this riddle knew that lots of people don't think so good.

LOL! Yeah.

Truth is, this was probably taken from some first year physics text book. My Freshman year physics prof used to put questions like this on the tests. If anyone even attempted an answer, you got the problem wrong. The only correct answer was "there is not sufficient information provided to answer this question". If you made the above statment then provided hypothetical numbers(xyz ft/lb thrust, xyz coeficient of friction, xyz coeficient of drag, etc) and *then* came up with an answer, you got extra credit, provideing the answer was correct.

[The AD]

In all practicality, the plane will take off as normal, only with it's wheels spining at twice the normal speed, anyone who sees otherwise is so patheticly stupid that it's really very very hard to fathom.

Well that fucking does it, I just got called pathetically stupid by DINMS!

After thinking about it for the night, though, I have to admit the airplane on a sloped ramp is pretty convincing. Yes, the treadmill would provide some force to resist gravity pulling the plane downhill, but if it could only go as fast as the airplane there's no way it could prevent the airplane from falling.

So I think the fact that we're talking about a 747 is critical because the landing gear friction will be << the engine thrust. If the problem was just "an airplane" you could say, well it might be a toy airplane with really bad wheel bearings and then there's no way it could get in the air.

[acostiga]

i don't have the energy to read through the entire thread, so can somebody just tell me if the question involving knight rider and kitt was answered? how could kitt go from moving at highway speeds to just stopping so quickly? the car and the truck are both moving fast, relative to the ground. then, kitt pulls onto the truck and is able to almost instantly stop moving relative to the truck? is there like an aircraft carrier cable/pulley system at work there?

also, just how many pocket protectors were ruptured at some point during the development of this thread? in any event, i'm glad that there are people with minds for these kinds of problems so that i don't have to haunt myself with such things

[focus]

Someone said something about a car driving on a trailer at highway speeds, early in this thread, before I lost so many IQ points. The engine would probably die as soon as it hit the trailer.... asuming you didn't simply take your foot off the gas and shift into first.... *rolleyes* Asuming you weren't a 'the plane would not fly person' and took your foot off the gas and coasted onto the trailer, the only forward force would be the momentum of the spinning tires and the engine idling.

Or you could just push the clutch or throw her in neutral.......

[focus]

This thread is absolutely blowing my mind. Is this that difficult?

A plane (747 passenger jet) is sitting on a runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the planes speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).

The question is:

Will the plane (747 passenger jet) take off or not?

Yes, the treadmill would provide some force to resist gravity pulling the plane downhill, but if it could only go as fast as the airplane there's no way it could prevent the airplane from falling.

So I think the fact that we're talking about a 747 is critical because the landing gear friction will be << the engine thrust. If the problem was just "an airplane" you could say, well it might be a toy airplane with really bad wheel bearings and then there's no way it could get in the air.

why is everybody so hung up on wheel speed = plane speed? THE CONVEYOR CANNOT MOVE IF THE PLANE IS NOT MOVING FORWARDS. How does the conveyor belt know how fast to roll to counter the plane's forward movement if the plane isn't fucking moving? The conveyor IS NOT hooked up to the forward force of the plane. The conveyor IS NOT hooked up to the wheel speed of the plane. The conveyor IS NOT hooked up to the forward motion of the plane as it relates to the conveyor belt! The conveyor is not hooked up to keep the plane in one place, it only moves as fast backwards as the plane is moving forwards.

it doesn't matter if it's a 6" long model fucking airplane or a wind-up toy car.

i'm pretty dead frickin positive that the bearings on any plane can stand up to at least twice take-off speed. The wheels too, for that matter.

If the conveyor is providing equal but opposite movement to what the plane would have if it were on solid non moving ground, the plane, in relation to everything (the ground, air, surroundings) except for the conveyor, isnt going to be going anywhere. The only thing moving is the wheels, and wheels dont make an airplane fly.

Where did you read that in the question? You totally just made that shit up! how...HOW....would the conveyor belt know how fast the plane would be moving if "it were on solid non moving ground? and WHY would it matter? conveyor belt says "the plane will be moving at 300mph" and goes 300mph backwards... wheels move at 600mph -- but the plane still moves at ~300mph forwards! This is the only condition that makes the friction of the wheel bearing even moderately relevant...but it's still a relative nonissue. It's also one of the only conditions that would keep a car from moving forwards.

mind = blown; this is right on par with the "wiping ass" thread.

[Franz Klammer]

Just to clarify: did we reach a final conclusion in this scenario?

1) wheels of jet plane are locked (note: this is just a simplifying assumption to state that there is some friction)
2) jet plane thrust is limited
3) treadmill is spinning at infinitely high speed
4) treadmill is infinitely long

As I understand, if the jet plane thrust is large enough, the thrust will eventually overcome the frictional force (which is bounded) and so the plane will eventually move forward and take off.

Also, here is a variant of the original question which one of my friends suggested after I told them about the original "jet plane on large treadmill" problem:

Same scenario as before, but now you have a car with wings attached sitting on the treadmill. Will the car take off?

I think I know the answer, but let's keep this crazy thread going.

[f2f]

if everyone keeps posting in this thread there'll be no snow for the PNW this winter! and if Newton keeps spinning in his grave at current rates, he will generate enough heat to prevent any snowfall for north america next winter.

[Will]

Dear God.... I ran from the sciences like a scared little bitch in college. I only took regular physics, never AP, in high-school.

...but apparently I understand physics a lot more than any of you. Jesus.

By the way, this is the funniest pic I have yet to see on TGR:

[The AD]

Just to clarify: did we reach a final conclusion in this scenario?

1) wheels of jet plane are locked (note: this is just a simplifying assumption to state that there is some friction)
2) jet plane thrust is limited
3) treadmill is spinning at infinitely high speed
4) treadmill is infinitely long

1) not sure what you mean by locked, but it is a real plane (747), so we shouldn't assume some hypothetical frictionless bearing scenario.

2) Yes, again it specifically states it's a 747.

3) No, it's only spinning at the same speed as the airplane. We can assume it's capable of any speed, since no upper limit was given.

4) Well it does say it's a runway, so assume it's pretty long. Since no length is given we can't exactly conclude that the plane will fall off the end.

[Will]

btw - I just dumped this lil' question over on telemarktips. I wanna see what they think. Now someone go put it on epicski.

http://www.telemarktalk.com/phpBB/viewtopic.php?t=15412

[Franz Klammer]

1) not sure what you mean by locked, but it is a real plane (747), so we shouldn't assume some hypothetical frictionless bearing scenario.

2) Yes, again it specifically states it's a 747.

3) No, it's only spinning at the same speed as the airplane. We can assume it's capable of any speed, since no upper limit was given.

4) Well it does say it's a runway, so assume it's pretty long. Since no length is given we can't exactly conclude that the plane will fall off the end.

Dude, I didn't ask you to comment on my assumptions, but rather on the conclusion.

[Squatch]

i don't have the energy to read through the entire thread, so can somebody just tell me if the question involving knight rider and kitt was answered? how could kitt go from moving at highway speeds to just stopping so quickly? the car and the truck are both moving fast, relative to the ground. then, kitt pulls onto the truck and is able to almost instantly stop moving relative to the truck? is there like an aircraft carrier cable/pulley system at work there?

also, just how many pocket protectors were ruptured at some point during the development of this thread? in any event, i'm glad that there are people with minds for these kinds of problems so that i don't have to haunt myself with such things

It is possible. Anyone who rides bike trainers can tell you so...if you've ever ridden a roller-type trainer and fallen off, you'd know extra-well, like my roommate.

Or, imagine you are running at 10 mph on a treadmill. Now jump off the treadmill sideways onto the ground. You stop, instead of flying forward if you had been really running. That is because, on a treadmill, your only momentum is zero related to the frame of reference (I.e. the ground) save for the motion of your legs. So when you jump off sideways, it's easy to stop quickly because you weren't actually moving in the first place, at least as far as the ground is concerned.

Now for the Knight Rider question, you need to look at frames of reference. The truck is doing 80 mph, and Knight Rider is doing, say, 83 mph. The difference between the two is only 3 mph, so when Knight Rider "stops" he is actually only slowing down three mph. Pretty easy to do, especially at 80 mph. The speed relative to ground doesn't matter, just as it doesn't matter that the eart is hurtling through space at high speeds.

A similar way of looking at it would be Knight Rider driving on a treadmill, with the truck parked immediately in front of it, off the treadmill. Knight Rider goes slightly faster than the treadmill, accelerates off it, finds his speed relative to ground is the difference between him and the treadmill speed, and realizes his "actual" speed (relative to ground) is very low, so it's easy to stop.

[Art Shirk]

What happens if you are traveling at the speed of light and you turn on your flash light? What if you point it behind you?

[Squatch]

What happens if you are traveling at the speed of light and you turn on your flash light? What if you point it behind you?

it's cool, man, it's an infinitely long and infinitely large flashlight. so basically it gets to do whatever the hell it wants (based on the 800-lb gorilla postulate).