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IF YOU SLID A 100MPH TREADMILL UNDER A STATIONARY PLANE, WILL IT SLING BACKWARDS??????
NO! IT WILL SLOWLY BEGIN TO MOVE BACK BUT RELATIVLY STAY IN THE SAME AREA.
NOW ADD JET POWER TO THE PLANE AND WATCH IT BEGINE TO RACE FORWARD EVEN WHEN THE TREADMILL IS ON.......
you stupid mother fucker lol jk
The entire point is that it doesn't matter if they are equal or not. It doesn't matter whether or not the belt is moving the same speed as the plane. It could be moving faster or slower and it won't make a difference, because the only thing that the belt does is move the wheels and the wheels spin independant of the speed of the plane.
:goodjob:
oh ok...i understand now...i can grasp it easier with a jet engine example but for some reason the propeller engine seems to be like hitting two bricks to gether...i'm not getting anywhere.
from how i see it, the wheels are the only thing moving on the plane...the wheels are going the same speed as the treadmill so the plane is continuing to occupy the same space (as stated in the question). if the plane isn't moving foward or backward because of the treadmill then it seems pretty stationary to me...i just don't understand where the lift comes from. the engines provide the thrust but it seems to me that only when the plane is actually traveling from say point a to point b that the air would move across the wing, without the air moving across the wing (because its stationary) i don't see where the lift comes from....make anymore sense or is it still not stationary??Quote:
Originally Posted by joecoolfreak
i'm not trying to be a smartass but can someone please explain where the lift comes from?? i really want to grasp the concept, it's fustrating me, haha
and do those rubberband planes really take off from the ground??? i've always wound them up and thrown them off a deck or something...
Ok...I will try this again. Plane is standing still on a runway which works like a treadmill. Plane starts engine and begins to move forward. Thrust is provided by propellers or jets, doesn't matter. Forward motion has begun. Treadmill now begins to turn because plane has speed (otherwise known as motion). Plane continues to speed up due to thrust of engines. Treadmill continues to speed up as well. The only thing that the treadmill touches on the aircraft is the wheels. As defined by the original question, the wheels are free spinning, which means that they are not part of the drivetrain of the aircraft and provide no thrust, and they have no resistance which means that they can spin as fast at they want. By the time that the plane is traveling 100mph, the treadmill is going the opposite direction at the same speed, therefore turning the wheels at the speed of 200 miles per hour. Once the plane reaches it's lift speed, it will take of just like any other plane because of the lift of the air moving past the wings. Keep in mind, this treadmill is just as long as a regular runway and the plane moves from one end to the other and there is air so the plane will take off just like a plane would on a regular runway.
well that kinda makes sense, but the plane would have to work harder to take off...Quote:
Originally Posted by joecoolfreak
but i am under the impression that the plane isn't traveling down the runway since the runway is going the same speed, weather it be 500 miles long or 500 feet long, i thought it was just sitting in place with the ground (treadmill) moving under it....so the air isn't moving at all
The plane would have to work harder...but that amount of harder would be so miniscule because the only thing that it is doing is over coming the initial rolling drag of the wheels. Take plently of the examples that have been given so far in this thread. Put a skateboard onto a treadmill at the gym and see how hard it is to hold it in place while the treadmill is moving. Increase the speed of the treadmill and it is just as easy to hold in place. A pinky finger could do it. Now slightly push the skateboard forward as the treadmill is moving and you will find that you have to push just as hard as if it weren't moving. It really doesn't make a difference and it also doesn't matter how fast the treadmill moves. The reason why is the thrust forward is coming from your hands and not the wheels. The wheels are there just so that there isn't any friction between the board and the treadmill and it doesn't matter whether it is this example or a plane...same concept.
If you put a plane on a treadmill and start the treadmill it will initially move backwards. If you start the engines, it will move forward, there is basically no way to keep the plane motionless in respect to the ground. That being said, we think of speed like our speedometer in our cars, but a planes measures it by airspeed, therefore to say that the treadmill is matching the speed of the plane, it must be moving releative to the ground, not the belt of the treadmill and therefore would have drag and lift etc...
Quote:
Originally Posted by joecoolfreak
it would be stationary because the treadmill is moving...not the plane. the only lift would be through what little wind the propeller threw over the wings
damn did u read my post? i made it fuckin huge font for a reason
THE TIRES IN NO WAY ARE DIRECTLY RELATED TO HOW FAST THE PLAN IS TRAVELING
I give up...I have been trying to help ya'll get it all day long, but I guess I have failed.
What you are failing to grasp is the concept that the wheels will spin faster, but that's it. The plane will still move forward. :)Quote:
Originally Posted by chuck
Like I said earlier:
Take a hotwheels/matchbox car and push it on a piece of paper.
The car represents the plane, it's wheels represent the FREE ROLLING wheels of the plane, your arm represents the force of the engine pushing the plane, and the paper represents the treadmill.
Pull the paper backwards while pushing the car forward. Do you feel ANY pull on the car? No. Did you notice that the car's wheels spin faster? Yes. Do you need to exert MORE force to push the car? No. No matter how FAST you pull the paper. the same force is needed to push the car.
[/thread]
Think of it with respect to a wheelchair on the treadmill.
You're sitting in a wheelchair on a treadmill. The wheelchair wheels are free-spinning, meaning they turn w/o friction.
I stand behind you in the chair and place my arm behind the chair and hold you in place.
You power on the treadmill, and the treadmill starts to move backwards. But I just hold you there w/ my arm extended, and only the wheels spin.
The treadmill moves faster. I don't have to hold you with any more force than I am already exerting* --> the wheels just continue to spin faster and faster. Work is done by the treadmill on the wheels, but there is no force increase whatsoever on the wheelchair to my arm since the wheels are absorbing all* of the energy. The ONLY function of the mill gaining RPMs is spinning the wheels faster.
Now say I walk alongside the treadmill and push you along forward (me pushing you = thrust from the airplanes engines). The speed you move forward is completely independent of the speed with which the treadmill turns. The speed you move forward is only relational to how hard I push you (how much thrust the engines exert). If I push slow, you roll forward slow. If I push you fast, you move forward fast --> no matter HOW fast the treadmill turns.
This is basically the same thing that's happening to the plane, because the engines are pushing you relative to the air, not the ground!!
* (actually I do have to apply a SLIGHTLY greater effort to keep you motionless b/c we currently do not have ANY wheel bearings that are 100% efficient, nor is the transfer or motion from the treadmill to the wheels 100% efficient, but you get the idea). THE PLANE WILL ACCELERATE AND FLY ONCE YOU START THE ENGINES, w/ the only difference being the tires are rotating exponentially faster.
NOW --> /THREAD
Quote:
Originally Posted by Ruiner
aight aight...i get what you guys were saying now...i was thinking the planes ground speed was constantly the same as the treadmill, like running on a treadmill, you don't actually go anywhere....but yeah, i see how the force of the thrust can move it forward with the treadmill still going the opposite way with free moving wheels
...i guess i just had a misunderstanding of the "while the conveyer moves in the opposite direction at the same speed as the plane"
but i still have questions...even though they weren't asked for...
so if the plane and the treadmill are always at the same speed then how does the plane move?? say the plane pulls foward at 5mph, the treadmill would go backward at 5mph, i'm assuming the wheels would be spinning at 10mph but the plane would be chilling there??
i get the concept that the plane can move foward but i don't get how it could on a treadmill going the same speed but backward...i think i'm getting mixed up in the plane speed, wheel speed and treadmill speed...grrr
lolQuote:
Originally Posted by chuck
RG notes:
ok picture a beautiful field and a bunny rabbit hopping in the forest. Now in that field, picture an airplane lifting off normally.
Now picture a conveyorbelt where the runway is... and moving inverse of the speed of the wheels. The plane will still lift off normally.
The plane doesn't do burnouts before starting to lift off for traction, since the plane is not powered by the wheels man. :)
What color is the rabbit?? :thinking:Quote:
Originally Posted by RaИdomGuy
purple with neon green polkadotsQuote:
Originally Posted by BABY J
*Request to start banning people that dont understand it*
i understand what you guys are saying, i think i'm just reading too far into the question for my own good...i swear i'm no fool, its been on my mind all day, i'm sure at some point it'll hit me and i'll feel like an idiot...or may we're both right and talking/thinking about two different things (plane speed/wheel speed) the question says plane speed so i was going with that...Quote:
Originally Posted by TheSnail
maybe i just need to swing out to the HS and pay the old physics teacher a visit...
chuck! please, you're smarter than that. It doesn't matter if the conveyor belt is going slower, the same speed, or 100x faster than the plane. It will still take off just like any runway in the world. The wheels are free wheeling and the planes power/thrust comes from above it...two completely differant sources of energy. The only thing the speed of the conveyor belt will have an effect on is what speed the wheels on the plane are free wheeling.Quote:
Originally Posted by chuck
As i mentioned yesterday. Imagine sitting on a skateboard on a treadmill with a rope tied in front of you...like you're being pulled on a sled behind a 4 wheeler. Now someone turns it on and you're still just sitting there stationary as you hold on the rope right (just spinning the wheels). Then the speed is increased....do you go backwards? nope, it only makes the wheels spin faster. Do you think it will be any harder to pull yourself forward or hold yourself stationary? nope, just the same as 1mph or 14mph. Now imagine if someone came up behind you and shoved you....would you and the skateboard still roll forward? That force of the person pushing you is no differant than the prop or jet of a plane.
Echo, have you slept on it and come to your senses?
Are you guys actually going to test this?
I'm not sure how accurate the test would be to tell you the truth, someone like Mythbusters needs to take it on. A model plane is going to be so light that it can take off from a standstill, it needs weight and a type of plane that actually needs a runway to take off. I searched on Mythbusters site and there was a 50+ page thread on this, it's now locked so maybe they are actually going to do something with it.
With a budget and a small plane, it could be done. I seriously doubt there is any way to test this truly with a large plane though. A 4000 ft long conveyor is just not going to happen.
I'm all for testing things, but I want it done right or it means nothing.
I agree Jenn. I was going to do it sometime today, but echo never called. I still can't understand why anyone can't understand the theory behind it all. Everyone gets hung up with the speed issue and seems to think that the plane isn't moving relative to the ground and that just isn't possible. If anyone truly steps back from the equation and looks at Ruiner's, or BabyJ's, or Speed's, or my examples from previous post's you don't even need a plane to see what is going to happen. A skateboard or a wheelchair prove the important part. I think at this point, everyone will agree that if the plane moves forward, it will take off, so all you have to do is ask yourself, will the plane move forward? At that point, you don't need a plane or a 4000 ft treadmill to understand what will happen. Just find something with free spinning wheels or as close as you can and put it on a treadmill. Turn up the speed and see how hard it is to push it forward and then conceptualize in your mind that pushing forward is the exact same concept as a plane's prop or a jet's turbine. It doesn't take much effort to push your skateboard or wheelchair and so as soon as the aircraft's engines engage, the aircraft will take off just like normal. It's really the speed thing that trips everyone up. Think for a second on being in a car on a dyno...At full throttle, the car's speed is still nothing. In order for the car, or in this case, the plane to have speed it must move forward in respect to the ground. If it doesn't and stay's stationary, then by the rules set up by the original question, the treadmill is also at a stop. That is the only time that anything is stationary.
im skippin like, 15 pages of this thing, I just hope people realize it won't work. you need air running over and under the wings to create lift, more specifically, more air running over the top of the wing than the bottom of the wing. now on a treadmill, the plane techinally would not be moving anywhere since it is on a treadmill, yes the wheels are moving, and yes, the jets are psuhing it to keep it on the treadmill, but you still have no air moving over and under the wings. Somebody said it earlier, if you run on a treadmill, there is no wind, same for the plane. It doesn't matter how much thrust the jets are putting out, or how fast the wheels are turning, all that matters is how much air is traveling around the wings. I'm sure there is at least one smart person who explained this already, but if not....
/thread
Quote:
Originally Posted by joecoolfreak
you can't compare an airplane to a sakteboard, or wheelchair, or car, because of the fact they do not have wings! like I said in the previous post, the wheels of the plane can be spinning at 1000000000mph, but if there is no air moving over and under the wings, you cannot create any lift.
It will work...read the thread carefully...or for that matter read the last post before your's...learn something new =-)Quote:
Originally Posted by buffdaddy18
*sighs*
I am using the other models as an example to prove that the object, whether or not it has wings will move forward. Once you understand that little piece, you will realize that if it is moving forward, the air moving will create the lift required.Quote:
Originally Posted by buffdaddy18
you are still missing the point that the speed of the wheels does not make a plane take off.Quote:
Originally Posted by speedminded
No, you are missing the point that the speed of the wheels is not the speed of the plane.Quote:
Originally Posted by buffdaddy18
Edit: Planes do not judge or measure speed by their wheels.
Quote:
Originally Posted by joecoolfreak
ok. so imagine this, you are standing to the side of this airplane on a treadmill...... the treadmill is going backwards at 500mph, the plane is producing a thrust to make the wheels spin at 500mph....... is the plane not staying in the same place? yes. so where is the draft to produce lift coming from?
A planes engine does not provide thrust to the wheels. That is why the examples prove the point. Look at the skateboard example again. Turn the treadmill on to full blast and use your hand to hold the skateboard steady. You barely have to hold on to keep it in place, now push forward. That is what the engines do in a plane and you will see that the skateboard now moves forward...hence our movement and then you have lift.Quote:
Originally Posted by buffdaddy18
Quote:
Originally Posted by joecoolfreak
ok, so then i am on this treadmill on a skateboard, now if I need to get up to 100mph (that means actually moving forward, not sitting in one place) on my skateboard, having a treadmill under me will do nothing for me, if not impede me. The theory is still flawed. If a plane needs to travel 500mph (not sure how fast it has to go, just using a random number) to take off, and if it is sitting on this threadmill, and the jets produces enough thrust to propel the plane at 500mph, but ther ground underneath the plane is moving in reverse direction at 500mph, then the plane, technically, is not moving. And if the plane is not moving, there is no air traveling over and under the wings, which is needed for lift. So since there is no air traveling over and under the wings, there is no lift.
Here, do this. take a piece of paper, tape two ends together, stick a pencil through the open end. now hold the pencil parallel to the ground, and blow over the paper. the paper rises because the air pressure over the paper was less than what was under it. now put wheels on each end of the pencil, tie the pencil to the front end of the treadmill, and turn the treadmill on. I will garuntee that the paper will only drag against the treadmill.
ok, now that I have been informed that this hypothetical treadmill is the length of a normal runway (missed that part in the original post), where friction is not an issue, then yes, the damn plane could take off. It's just when I saw treadmill, along with when a lot of people see treadmill, I think of a person running in the same spot, not trying to run forward. So in essence, both answers are right for this question, depending on your view of the treadmill.
We achieve forward motion.Quote:
Originally Posted by Ruiner
Forward motion moves the airfoil (wings) through the air.
Air foil moving through the air creates high pressure under the wing, low pressure above the wing.
That pressure differential = LIFT
LIFT = flight: in SLIGHTLY farther distance than normal, due to wheel bearings not being 100% efficient and friction between tires and conveyor belt (negligible; engines will still EASILY overcome this)
-- You are now free to move about the cabin. Chicken or beef sir?
What do you mean now that you have been informed? The question is exactly the same as it was the minute it was posted...BUT doesn't really matter the size, if it's smaller than the required length to take off then the plane will simply run off the end of it. No matter how fast the conveyor belt is going NOTHING is going to prevent the plane from moving forward....nothing at all. The plane pulls or pushes itself via air....just as your arm can pull yourself if you are sitting on the skateboard on a treadmill. The conveyor belt has absolutely no effect on the airplane because the wheels of a plane are free spinning.Quote:
Originally Posted by buffdaddy18
No. Planes are NOT All-Wheel Drive. They are front-wheel driven. Later, QD.
But wait. Is that w/ LSD or no? :thinking:Quote:
Originally Posted by Stretch®
^^^ That was stupid. I was being serious. I have 2 airplanes. And I don't mean models or RC. I would know. Later, QD.
I hope you are kidding man. You're confusing ME. NEway.
Plane will fly.
/thread