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LAN Party Forums => Jokes and Fun => Started by: Pride on December 29, 2005, 08:21:34 AM
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Not so much a joke but rather a concept question:
A plane is standing on a runway that can move (some sort of band conveyer). 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 opposite direction).
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No, it won't. It needs lift from air to put force on the wings. If it's not moving forward and only has its wheels moving then air isn't passing by its wings.
Unless of course it has vertical takeoff capability.
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If the conveyer and the plane were going the same speed in opposite directions, the plane would stay in the same place.
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Are you positive of this? Think REALLY hard about it!
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Pride...He's "elite" on these thinking questions... :2thumbsup:
*"elite" referring to Hackers...the movie :bigsmile:
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Pride...He's "elite" on these thinking questions... :2thumbsup:
*"elite" referring to Hackers...the movie :bigsmile:
what about us who are elite in real life?
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The plane will take off...Here is why
Lets start by looking at a car in the situation instead of a plane. In a car, the wheels are what drives the car foward. In this case, the car would remain in place relative to the conveyer belt due to the belt moving in the opposit direction.
Now, in the case of the plane, the wheels do no driving at all. The wheels are only there to reduce friction between the ground and the plane itself. The actual force that moves the plane is that of the jet engine sucking in air from the front and pushing it out the back.
Just a little more explaining to do, and then all will be understood.
If you sit a car on an icy lake that has 0 friction between the wheels and the ice, the car will not move. This is because the force that makes a car move the friction between the rubber tires and the ground. With the plane, the wheels do not drive anything, they simply help the plane roll along. So, a plane sitting on an icy lake can take off even if the wheels have no traction.
So to sum it all up...THE PLANE WOULD TAKE OFF IN THIS SITUATION.
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I missed the part in the OP where it said this plane had a jet engine. Was that to be assumed?
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I missed the part in the OP where it said this plane had a jet engine. Was that to be assumed?
I used that as an example, but it would be the same thing with a propeller driven plane.
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Does a plane's thrust propel it? Yes.
But does the thrust lift if off of the ground? No.
The wings need air to flow over the wings, and in turn the flaps to create lift. Without lift, the plane will simply match the speed of the conveyor belt and remain stationary.
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So I was right? Do I win one of those cheapo Geforce 7800s?
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:no:
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http://www.rx7club.com/showthread.php?t=491089&highlight=engineers
my brother adds this
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gotta log in
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it does actually work.
Let me explain differently.
The fact that the ground is moving does not matter. The wheels are free spinning and have nothing to do with the plane actually "moving"
In order for the plane not to move, the belt would have to move ALOT faster than the plane is.
let this video explaine it
video (http://videos.streetfire.net/player.aspx?fileid=35E964D9-38DB-4EFD-BE8D-D6BA1A43A06B)
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All that proves is that the paper wasnt being pulled away at the same speed as the fan blowing air...
Here is the key part of the original question:
This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in opposite direction)
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Let me try and put this in a different perspective.
The plane relies on thrust, through the form of displacing air, to move. Displacing air, has nothing to do with the ground. Right.
Its wheels are there to minimize friction between it and the ground.
Now, replace the airplane with a skatebaord, kinda like Billabond did. It's much like the airplane, only it lacks something to make it move.
And now, replace the runway with a treadmill...pointing almost straight down, with the conveyor moving upwards. That way, the skateboard has something to propel it, namely, gravity, which is also independent of air. If you set the skateboard on it and program it to increase its speed to match teh skateboard's while the skateboard accellerates, it won't stop it.
The wheels can not generate enough friction to counteract the force causing it to accellerate...the plane is designed so that the wheels do not have enough friction to stop it. If you had the treadmill spinning at 30mph, several times the skateboard's downward velocity, the skateboard would still fall.
Thus, the skateboard is moving relative to the air, as would the plane, because there is not enough friction in the wheels to keep it from moving.
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:hitself:
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that is exactly what i was trying to say...thus the plane would move and it would generate lift and therefore it would fly.
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But the plane isnt moving. If you were to stand on top of it.. .it wouldnt go anywhere! And you wouldnt feel any wind.
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But the plane isnt moving. If you were to stand on top of it.. .it wouldnt go anywhere! And you wouldnt feel any wind.
And why is it not moving? The conveyor belt can not create enough friction with the wheels to exert the force needed to keep its engines from moving it, just like the treadmill, no matter how fast it's moving, can not generate enough friction with the skateboard wheels to keep gravity from moving the skateboard like I said above.
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U guys are all geeks...only fites would discuss such a topic...will agree with Biggles on this one (after taking 10 min to read all the posts for this topic)
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friction has nothing to do with it.
The only thing that lifts a plane off of the ground is air flowing around its wing. the flow of air has to be so fast or the wing wont generate lift.
So unless you have a giant fan blowing air in front of the plane... it wont lift off the ground. I dont get why this is so hard for some of you to comprehend.
The speed of the "treadmill" and the speed of the jet engines are cancelled out in this question... since the treadmill is automatically adjusting to equal the speed of the jet propulsion.
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It really doesn't matter if the plane takes off or not.....................the airlines will STILL loose your luggage....................
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since the treadmill is automatically adjusting to equal the speed of the jet propulsion.
The velocity of the jet exhaust and the forward velocity of the plane are completely different which matters because...
This conveyer has a control system that tracks the plane speed
PLANE SPEED meaning forward velocity of the aircraft, not the velocity of the air being thrusted.
Your scenario of the conveyor cancelling out the thrust of the jet engines would work if
1. the conveyor applied an equal force to the aircraft in the opposite direction and
2. if the plane was bolted to the conveyor, so it could apply the force without any loss of energy.
Even if the conveyor IS going as fast as the jet exhaust, it can not apply enough force to the aircraft in the opposite direction because the wheels prohibit it from doing so...the force of the conveyor is being used to spin the wheels, not to push the plane.
That's what friction has to do with it...the wheels reduce friction to the point where there is not enough of it to transfer the force of the conveyor into the airplane.
It's as if you put a car on a dynomometer and drenched the tires in grease...you wouldn't be transferring nearly as much energy into the dyno because there's not enough friction for an efficient transfer of energy.
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/me continues to argue with pride
The plane would actually be moving. The fact that the belt moves the same speed as the plane does not matter. The wheels would just end up spinning faster as the plane moves faster.
A plane isn't driven down the runway because the wheels move, the wheels move because the plane is driven down the runway buy the thrust from the engines.
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define moving....
if I can point at an object for 1 hour and I dont move my finger... is it moving??
sure, the wheels are in motion... but the plane isnt actually moving. lol
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yes the wheels are spinning. The plane is also moving in the direction that the plane is ment to move.
after this thread was started, i found this (http://www.quakecon.org/forums/showthread.php?t=4890&page=1&pp=10) thread in the quakecon forums. read what they have to say (masteryoda knows what he is talking about).
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Put simply, the conveyor ain't doing s*** cuz of the whizzles.
good quote from MasterYoda:
Look at it this way. Stand on a treadmill going full speed while wearing rollerblades, tie a rope around your waste, and have someone standing in front of the treadmill pull on the rope...will you move forward? yes
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The truth is, you guys can argue all day long... but the fact is.. the plane will NOT take off.
I dont know how else to put this...
If the tread is moving backwards at 100 MPH, and the wheels are turning at 100 MPH, the plane is NOT moving.
In order for a plane to lift off of the ground, it must have a significant amount of air flowing over the wing to create the lift when it hits the flap.
If the plane is not actually physically moving, then no air is flowing over the wing.
I think what you are all forgetting is that Jet Engines do NOT create lift. they simply push the air behind them allowing the plane to thrust forward, in turn causing air to flow over the wing, in turn giving lift.
So essentially, the Treadmill is counteracting the Jet Thrust... and in turn the plane is NOT moving!
No plane movement, no air over the wing, no lift.
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(http://pride.fites.net/images/planetread.jpg)
Without movement, no air goes over the wings to provide lift. Plane is stationary.
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Just as I said.....................
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Please note.. I love to debate... so dont take anything personally... :2thumbsup:
Put simply, the conveyor ain't doing s*** cuz of the whizzles.
good quote from MasterYoda:
Look at it this way. Stand on a treadmill going full speed while wearing rollerblades, tie a rope around your waste, and have someone standing in front of the treadmill pull on the rope...will you move forward? yes
The problem with this quote is the fact that there isnt "grounded" adding force to the plane. The plane's only force is the jet thrust which is counteracted by the wheels going the same speed in the opposite direction because of the treadmill.
Sure, in this example, if you tie a rope to the nose of the plane, and pull on it, with everything else being constant.. the plane would indeed move forward.. but that is not part of this situation.
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Look at it this way. Stand on a treadmill going full speed while wearing rollerblades, tie a rope around your waste, and have someone standing in front of the treadmill pull on the rope...will you move forward? yes
Actually, Pride, thinking about it more now I have to agree that it WILL take off. Think about it this way. If the plane is providing thrust to move at 5mph the treadmill will counteract that by moving 5mph. The wheels however will be moving at 10mph. Why is that? Like has been mentioned by others here the wheels are basically frictionless in regards to the thrust of the plane. They will not slow it down. The engines on the plane will push through the air while the wheels do no pushing at all. They merely keep the planes fuselage from sliding on the ground. As the plane and the treadmill move faster the rate the wheels are traveling will be the combination of both the speed of the plane and the treadmill.
In your picture you drew (quite nice btw :bigsmile: ), where it says the thrust is pushing backwards it is doing so in regards to the air. The treadmill is not applying any force against the plane to slow it down, all it is doing is making the wheels spin faster (in this case they're moving at 400 mph). Does this help make more sense of the problem?
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I fully understand your point... and I have thought of it from that angle.. however...
Think of it this way...
Take away the jet thrust for a moment... turn the engines off. If you turn on the treadmill... the plane will slide off of the treadmill at 200 MPH. Now... restart the plane... put it back on the treadmill... turn the thrusters up to 200 MPH.. and the plane should (in theory, when not taking into account friction) stay stationary on the treadmill.
If you want to factor in friction of the wheels... then remember that the treadmill will adjust to any speed necessary to counteract whatever force is being put on the plane.
The problem remains then... if the plane is stationary, no air is moving over its wings, and no lift is achieved.
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You're missing the part about friction on the wheels on the plane. It's basically non-existent. If the treadmill started going at 200mph the plane wouldn't immediately slide off the back. Its wheels would start spinning first and any friction produced by them would slowly accelerate the plane backwards until it fell off. The thrust from the engines would more than counteract this friction (if the wheels had that much friction on them then a plane would never be able to take off, even from a stationary runway).
However, the engines displace the air in front of the plane providing thrust. The push off is not on the wheels. The plane would have enough thrust to move forward and eventually have enough air passing the wings to provide lift. No matter how fast the treadmill is going (as long as it is matching the speed of the plane) the wheels would just spin. To stop the plane the wheels would have to produce enough friction to counteract the thrust, without brakes this would be impossible.
On a side note, how much are hotel rooms for the LAN party? :feedback:
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89$
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Thank you, G!
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you do realize that if you had told me prior to registering... i would have given you admission for free right?
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Crap. Well, I'm not decided on getting a room yet anyhow as I don't know if the wife is coming with or not. If she decides not to then I won't get one. I kind of forgot about the waiving thingy. Thanks Mr. Funkalicious :blamepride:
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i'd make a deal with ya that if you had a friend sign up... i'd give them free admission, and they can just pay you the 20
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If you want to factor in friction of the wheels... then remember that the treadmill will adjust to any speed necessary to counteract whatever force is being put on the plane.
Err, ok, if you look at the runway not being calibrated to the speed of the plane but instead to any force being applied to it...then yes. Your treadmill would be spinning insanely fast, but it would keep it from going anywhere.
If it's only spinning as fast as the plane is trying to move, it won't do anything, because the wheels don't allow it to hold back the plane.
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i'd make a deal with ya that if you had a friend sign up... i'd give them free admission, and they can just pay you the 20
I'll take a deal of a friend coming sign up (have 3 coming) :2thumbsup:
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F3ar0n..... you find a fourth, and he can give you his 20 bucks instead of to me!
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THe plane will take off. Period. End of discussion. The engines push the plane forward. When the treadmill tries to counteract the force of the engines, it has no way of "grabbing" the plane and pulling an equal and opposite force upon it, the wheels will simply spin. Since the treadmill can only cause the wheels to spin and not "pull" the plane backwards, the engines will continue to push the plane forward, creating lift over the wings (not the flaps, BTW, they create more drag on the plane when it is landing, you generally have your flaps in a neutral position when taking off and extended when landing) and causing the plane to lift.
There are 4 forces at work on an airplane at all times. An imbalance in these forces causes movement of the plane in the direction that is stronger than it's opposite force.
1. Thrust of an engine (pushing forward)
2. Drag of friction (usually of air, and in this case the treadmill)
3. Lift of the wings (lifting upward)
4. Pull of gravity (pulling towards the earth)
Looking at these four forces, the engines thrust forward, the treadmill tries to increase it's opposite pull, but it can't because the wheels will just spin and it can't transfer its energy to the plan itself. Thrust is the greater force and will propel the plane forward. As the plan moves forward, air begins to move over the wings and through the magic of the curved surface of the wings and Bernoulli's principle, lift greater than the pull of gravity is created, and the plane takes off.
The only way this plane would not take off is if the plane were on skis or the wheels were locked in place, or some other method of the treadmill to transfer its forces into the body of the plane, none of which is presented in the original question.
I won state level awards in school for my presentation/reports on airplane flight and balsa wood gliders I made and flew. Heck, I even got 9th at nationals one year. Just thought I'd throw some credentials in there.
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sully is the man...he know what he is talking about
:blamepride:
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LOL nice job sully, rheittorated what I said but with a pwnage way of explaining it.
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A jet will not take off, A prop plane will. Jet can't make it's own wind for lift. A prop plane can. Just kidding.
Just think, no matter how fast them wheels are spinning, to the rest of the world it's not moving. So you have no wind for lift.
How about this for an experiment. Take your stupid skateboard (I couldn't see the video.) put a paper airplane on it. Put it on the treadmill. Hold the back of the board so that it does not move but the wheels spin. (This is the jet thrust.) Crank that baby up... And you will have a paper airplane on a skateboard.
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Shado, how is a spinning treadmill jet thrust? There is nothing in your scenario propelling the skateboard forward.
FYI, I know you were kidding in your first paragraph about a prop vs. a jet, but I just want to get it out in the open, lift is not created by the force of jets or the wind from a prop, it is created by the flow of air over the wings caused by forward motion of the plane or an air mass moving around the plane. In theory, given a strong enough headwind a plane can "hover" off the ground. This is why it is preferable to takeoff into the wind and land with it (Point 5 (http://www.sportflying.co.nz/2.4%20BFT.htm)).
Although it is true the reversing speed "runway" will make it more difficult to takeoff, it will not hinder it completely.
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Am I the only one who noticed that the fan in the video was facing the wrong direction?
An airplanes propellers pull air while a fan blows air. With how you had it set up you should have pulled the paper from the other side.
Sorry but pride is right. My father was a pilot in the air force. Questioned him about it and he gave the exact same reason that pride is telling you. I allready knew he was right but I wanted to get some closure on it.
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lol.
i don't really understand some of this stuff, but i agree with pride.
not because of his scientific reasoning, but because of a thought that just ocurred to me.
if a jet could take off like that, why woulndn't they use it on aircraft carriers or somthing? it would take up less space right?
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argh, you guys really dug this up. Well, I will argue my point more if I have to. The plane will take off. It would take the same amount maybe a little more space to take off that it would on a normal runway, but it would take off.
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Pride is wrong on this one. The treadmill exerts no force on the plane, which he stated at the beginning saying that the treadmill matches the plane speed. A plane has no drive on the wheels so the speed of the wheels is irrelevant. The plane (jet or prop doesn't matter) will be pushed forward because it exerts it's force on the air. I think a better question would be this pride. A plane is flying into a 100 mph wind at 110 mph. How fast does the plane appear to be moving from the ground??
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OMG...Talk about a thread resurection from the dead. This hot debate is like 3 months old.
Anyways, lets let it R.I.P. but in anycase *cough* The plan would fly
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If a bear poops in the woods, and no one is around to smell it....what is the square root of Zero? :eek:
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14 :bigsmile:
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Mythbusters are testing this one on the show. I'll let you google the results.
Forum Necromancy FTW
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Looks like it has been resurrected once before...
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I just watched the episode. All I have to say is that I was right.
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Arghhh, you all beat me to this resurrection!
All I have to say is "Na na na na boo boo! I was right and you were wrong!" :nana:
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*yawn*
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I don't have the patience to read through 5 pages of posts, but whoever said the plane will not fly is right. Go to a gym and stand on a motorized tread mill, turn it on and start running, now run faster, unless there is a fan blowing on your face you should be feeling no wind, no matter how fast you move. It's the same with a plane. The thrust will try to make the plane go forward but this giant treadmill will keep it stationary. No wind, no lift, no fly.
OK I read back through some posts and am still confused...If the plane starts at a dead stop on the treadmill and as it gets thrust the treadmill matches the speed to keep the plane stationary how can their be air movement across the wings for lift?
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Do we have to get into this again?
Ok. First off, the plane did take off in the mythbusters episode.
The wheels simply provide contact with the ground so that the plane can roll. All of the drive is provided by the air moved by the prop/turbine. Just because the wheels are moving does not mean that the plane can not "pull "the air with the prop.
If you put on roller skates and got on a treadmill, then pulled your self forward with your arms, you would in fact move forward.
That make sense? The plane would take off.
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(http://forums.beyondunreal.com/images/smilies/deadhorse.gif)
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OK I read back through some posts and am still confused...If the plane starts at a dead stop on the treadmill and as it gets thrust the treadmill matches the speed to keep the plane stationary how can their be air movement across the wings for lift?
That is where you are wrong. The treadmill can't exert force on the plane itself to keep it stationary. It can only affect the wheels which won't slow the plane down. Whether the plane has wheels, skis, or pontoons they don't effect the plane moving forward due to thrust.
Yes I know this is beating a dead horse but hopefully this will put the debate to rest.
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Wow, talk about forum necromancy, whoever started this up again deserves to be staked! Put this topic to rest....
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Bill has it right..nuff said...
Leave this thread rest in peace
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ohh, ok..I assume the test was done with under wing turbines?...but if the plane was of the design of the F14 or F16 where the air was drawn in under the belly of the plane in front of the wings and out the rear behind the wings would there be enough air movement across the wings?
Sorry but I find physics fascinating.
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Why does it matter where the wind was drawn in?? The plane moves forward which creates the airflow over the wing which allows it to take off.
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I thought the plane was on a treadmill running backwards equal to the forward thrust of the plane hence keeping the plane stationary?
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No air movement = no high/low air pressure under/over the wing = NO FLIGHT. Basic physics....drop it already. Even a forward prop plane will not fly int hat situation, the prop ONLY provides reverse thrust (forward motion) and not the airflow over the wings. A plane on a STATIONARY treadmill will not fly.
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How does the treadmill keep the plane stationary?? A car on a treadmill can be kept stationary because it moves by turning the wheels. A plane uses a jet or prop to push it forward. The wheels just help it roll. The problem never states that the plane stays stationary. You assumed that.
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That is the point of putting a plane on the treadmill, to keep it stationary - to keep it from having forward motion. I didn't assume anything, that's just physics in motion (or lack of motion ;) ). I've seen/heard this 'teaser' before.
So what you are saying is essentially, the plane will have forward motion regardless of what the wheels are on? The point of having the treadmill is to keep up speed on the wheels so there is no forward motion. In actuality, there is NO motion relative to air/ground. Only motion relative to the treadmill, which (is supposed to) keeps the plan at a standstill. And again, we are talking about theory, which requires a perfect model of physiscs (no friction). This also is taking into consideration that the treadmill is programmed to keep up to speed with the plane, countering any forward motion, which would lead to the eventual destruction of the treadmill, and that inturn would let the plane have forward motion.
Now, if the treadmill is NOT a powered or programmed treadmill, then yes - the prop/enginge will produce thrust as normal and the plane will eventually overcome the counterforce of the treadmill (if there is any) and will take off as normal.
Two different interpretations of this teaser. That's one thing people usually don't mention when they ask you this - is the treadmill powered or not?
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Screw this, the plane and treadmill explode in a physics related debacle.....
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You know... I like physics as much as the next geek... but this is sounding a LOT like the "Schrödinger's Cat" discussions we had in school ><
(which is a mind-numbing topic, I might add)
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Question: Will the plane fly?
Answer: No one cares because there's no freakin' reason to put a plane on a treadmill in the first place (well, unless it's a jumbo jet).
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Not so much a joke but rather a concept question:
A plane is standing on a runway that can move (some sort of band conveyer). 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 opposite direction).
Drop it you both are right. But I think the problem is that we assumed that the treadmill would hold it stationary. It can't. You others who are so quick to also say, "I WAS RIGHT!" still didn't explain your reasoning correctly. Let it DIE!
Winning an argument on the internet is like winning the Special Olympics: You may have won but you are still retarded.
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Meh, it's all just theory anyway.....kill this thread!
Winning an argument on the internet is like winning the Special Olympics: You may have won but you are still retarded.
True true. LOL
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just a couple more pages and we beat the fake chick gamer thread.
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Then hell if it's only for page count. You can post. I will delete anything about the plane!!! HAHA
Crap does this mean I have to delete this before I post it?!
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Planes don't fly......
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and treadmills only keep items that use the ground for forward movement stationary.
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I vote for a (http://forums.beyondunreal.com/images/smilies/lock.gif)
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Winning an argument on the internet is like winning the Special Olympics: You may have won but you are still retarded.
Refer to above statement.