Yea I saw your pic and got the idea to do an image... but I figured without (what I think is) accurate physics, all the noobs are gonna come and say we are wrong hehe.bobby177 wrote:
What my picture was getting at with the FBD but I didn't wanna use numbers and formulasGotMex? wrote:
http://img155.imageshack.us/img155/2762 … illjy0.jpg
Any questions?
(Data derived from Wikipedia, Flight Simulation software formulas, and Physics 101)
LMFAO!!!!!!!!!!!!seymorebutts443 wrote:
what the fuck have you been smoking
Right........as soon as it hit 30 going downstream, it would generate enough lift to take off. But without the engine running, it wouldn't stay in the air for long, it would settle back down into the water. Got me on that one.JG1567JG wrote:
Correct on the first but think about the second one a bit. The plane only needs 30mph windspeed to take off.D6717C wrote:
It's gonna go backwords at 20 mph, and not be able to take off. If he turns downwind and kills the engine, he becomes a boat going 100 mph in the river's current.JG1567JG wrote:
Answer this then. A float-plane is going to try to take off going upriver on a windless day and the river was flowing at 100mph. The plane only needs 30mph windspeed to get lift off. The planes max speed is 80mph. What will happen when the plane trys to take off?
Edit--> Also what will happen if it turns downriver and cuts off the engines
Someone haas to have afriend with a RC airplane put it on a tread mill and see it fly. the tread mill would have to over come the free roll of the tires to affect the speed of the plane and at this speed the tread mill would create enough wind to allow for takeoff. as for the seaplane there's a reason why they stopped building large float planes( called clippers)
I AM!!!ATG wrote:
Kung Jew is gonna love this.
Plane wouldn't take off. But most of the confusion is due to stoner thinking when concerning the original expiriment.
So drink your Gin and Tonica, and smoke your marijuanica...
It's time for physics with ATG!!!
KJ
I don't see where friction would come into play because the wheels of the treadmill are tuned to turn at exactly the same speed as the airplane.
It's better to drink Green Tea and smoke Marijuana.... (IF IT'S ORGANIC DON'T PANIC)Kung Jew wrote:
I AM!!!ATG wrote:
Kung Jew is gonna love this.
Plane wouldn't take off. But most of the confusion is due to stoner thinking when concerning the original expiriment.
So drink your Gin and Tonica, and smoke your marijuanica...
It's time for physics with ATG!!!
KJ
Will be a cool experiment
Last edited by acidkiller187 (2006-12-27 08:21:03)
Say what? They're the same speed, but in the opposite directions, therefore the surface of the treadmill will oppose the turn of the wheels------this is friction. Other than that Bobbys animation pretty much explains it, except for a slight quip with the thrust of the engines equalling the friction. Friction is proportional to thrust in this instance, and a jet engine will provide a larger amount of thrust than the amount of friction, so they would never equal each other. Lets not have another 8 pages on this lol .ATG wrote:
I don't see where friction would come into play because the wheels of the treadmill are tuned to turn at exactly the same speed as the airplane.
A LEVEL PHYSICS FTW!
I know this is lengthy, but please read all of it before you respond to this.
let's state our knowns that most people have agreed on (except for those that still don't understand the basics of flight):
the wheels do NOT push the plane forward, they merely reduce the friction of the plane with the ground.
thrust does NOT make the plane airborne, the lift generated from the wing surfaces do.
airflow is necessary for an airfoil to create lift.
thrust allows the plane to move through the air, thus passing air over the wings, thus producing lift.
the friction from the wheels is negligable.
we are dealing with this problem theoretically, not practically; or else we'd have been done with this at the wheels failing due to their limitations.
the free body diagram that gotmex? drew up is correct. all the forces he has put on the plane are in the correct direction and the magnitude looks good. (the magnitude would make more difference if we were actually solving the equation)
so, based on what we've stated, i think it's safe to say we can simplify this problem into one statement:
Does the plane generate enough airspeed and lift (on the wing surfaces) to allow the plane to become airborne?
--------------------------------------------------------------------------------------------------------
I originally said 'no', but i'm unsure currently as i've read good arguments for both sides. so now i will go through my thought process and hope to come up with an answer (that will get contested either way).
Now, before i begin, i'd like to state the fact that i graduated with a mechanical engineering degree, so i have an understanding of forces and such (FBD's were my life). i also took the elective: aerodynamics, so i've got a basic understanding of that as well. so before flaming me, make sure that are at least taking a physics class before you do so.
---------------
from my personal experience, running on a treadmill doesn't produce hardly any airflow around me (unless you've got those little fans running). that was my reasoning for saying that the plane doesn't take off. no airflow, no lift, no takeoff. but let's analyze this a bit.
let's say the bearings in the wheels are perfect, and don't add any internal friction. in order for the wheels to rotate (and not slide), they must have friction with the ground. let me explain further. when dealing with a rotating object, there are two types of friction you need to worry about: rolling and sliding. in a more general sense, we have static and kinetic. static being the rolling friction, and kinetic being the sliding friction. for a tire, rolling friction is much less than sliding friction, otherwise, the tire would slide before it began rolling. when you hit a patch of ice, the sliding friction friction becomes less, and the tire wants to slide rather than roll because of the smaller coefficient of friction. this is also why your tire would rather roll than skid, and it only skids under high friction instances (braking hard for the neighbors dog, except if you speed up to hit it).
now we've established why the wheels roll. the friction with the ground allows the wheels to roll, and doesn't really contribute significantly to the entire system. and i've assumed we have frictionless bearings, for simplification. thus, we have a plane that is free to move in any direction.
forces :
thrust forward
drag backward
weight downward (this includes the acceleration of gravity. mass is constant, weight is not)
lift upward
normal force upward
basic physics states that the x-components and y-components of forces are independent. luckily for us, the force on the wing is a vector force, with a y-component acting in the upward direction.
at rest, the normal force equals the weight, because it is in equilibrium. for the wings to achieve lift, the thrust must be more than the drag, which it is, otherwise we wouldn't have mastered flight yet. this creates airflow over the wings, allowing the pressure to be less on the top, and more on the bottom. less pressure allows the plane to move upward. conversely, some race cars implement the same wings, but upside down to give it more downforce.
lift also must get to the point where is greater than the weight, because as the plane leaves the ground, the normal force no longer contributes to the system. this is achieved on a regular basis as all planes fly. as stated above, the y-component of the force of the wing becomes greater than the weight.
-----
under normal circumstances, the plane will be moving forward, so that the air flows over the wing.
Thrust > drag.
at rest, weight = normal force.
airborne, lift > weight.
during takeoff while still on the ground, lift and normal force = weight. the lift keeps increasing as the normal force continues to decrease.
ON THE TREADMILL
all of what i just stated works fine for typical takeoff. the treadmill makes things a little fuzzy. as aforementioned above, the bearings are frictionless and the wheels roll instead of sliding. the frictionless bearings allow the treadmill to match it's ground speed without any loss. so, the relative position, according to us, the bystander, is the same. the plane is not moving forward. the plane relative to the treadmill is different: it is moving relative to the belt position.
how is the plane staying on the treadmill and not moving backwards? the thrust generated by the engines. the thrust now is equal to the speed of it's wheels and treadmill, not necessarily overcoming drag like before.
the thrust force must translate to the speed of the wheels in order for the treadmill to keep it in place. this creates an interesting dynamic. is the ground speed the same as the airspeed? if so, half of you are right. if not, half of you are wrong. but i don't think this is the right question to be asking.
with that said, this could be rephrased to make even more sense and i think this is what we should have been asking in the first place. it becomes a question of relativity as much as airflow and airspeed. i take back my previous question at the top and replace it with this:
ARE THE WINGS MOVING RELATIVE TO THE SURROUNDING AIR?
i think that is the real question here. if the wings are, then the plane will have airspeed, and have airflow, and have lift on the wing surfaces. if not, the wings are in a stagnant surrounding of air with no airflow and no lift.
Here is my conclusion and I'm feeling pretty good about it:
Because the plane is moving relative to the treadmill, but not relative to the surrounding air, I support my previous answer with no, the plane will not take off. If you put the plane in a wind tunnel, the plane will have no problem getting airborne because it is moving relative to the air.
The air behaves similar to a fluid in that it is possible to have the air going through the engine, but not over the wings. This is why planes that have their brakes on with full thrust do not take off. Think about it this way: does a fan in your room move all of the air in one direction at that speed? No, it does not. It moves a localized amount of air to cool you off. There are gradients involved, and having the plane move down the runway allows the engines to pull the plane along so that the air can cover the entire wing surface.
let's state our knowns that most people have agreed on (except for those that still don't understand the basics of flight):
the wheels do NOT push the plane forward, they merely reduce the friction of the plane with the ground.
thrust does NOT make the plane airborne, the lift generated from the wing surfaces do.
airflow is necessary for an airfoil to create lift.
thrust allows the plane to move through the air, thus passing air over the wings, thus producing lift.
the friction from the wheels is negligable.
we are dealing with this problem theoretically, not practically; or else we'd have been done with this at the wheels failing due to their limitations.
the free body diagram that gotmex? drew up is correct. all the forces he has put on the plane are in the correct direction and the magnitude looks good. (the magnitude would make more difference if we were actually solving the equation)
so, based on what we've stated, i think it's safe to say we can simplify this problem into one statement:
Does the plane generate enough airspeed and lift (on the wing surfaces) to allow the plane to become airborne?
--------------------------------------------------------------------------------------------------------
I originally said 'no', but i'm unsure currently as i've read good arguments for both sides. so now i will go through my thought process and hope to come up with an answer (that will get contested either way).
Now, before i begin, i'd like to state the fact that i graduated with a mechanical engineering degree, so i have an understanding of forces and such (FBD's were my life). i also took the elective: aerodynamics, so i've got a basic understanding of that as well. so before flaming me, make sure that are at least taking a physics class before you do so.
---------------
from my personal experience, running on a treadmill doesn't produce hardly any airflow around me (unless you've got those little fans running). that was my reasoning for saying that the plane doesn't take off. no airflow, no lift, no takeoff. but let's analyze this a bit.
let's say the bearings in the wheels are perfect, and don't add any internal friction. in order for the wheels to rotate (and not slide), they must have friction with the ground. let me explain further. when dealing with a rotating object, there are two types of friction you need to worry about: rolling and sliding. in a more general sense, we have static and kinetic. static being the rolling friction, and kinetic being the sliding friction. for a tire, rolling friction is much less than sliding friction, otherwise, the tire would slide before it began rolling. when you hit a patch of ice, the sliding friction friction becomes less, and the tire wants to slide rather than roll because of the smaller coefficient of friction. this is also why your tire would rather roll than skid, and it only skids under high friction instances (braking hard for the neighbors dog, except if you speed up to hit it).
now we've established why the wheels roll. the friction with the ground allows the wheels to roll, and doesn't really contribute significantly to the entire system. and i've assumed we have frictionless bearings, for simplification. thus, we have a plane that is free to move in any direction.
forces :
thrust forward
drag backward
weight downward (this includes the acceleration of gravity. mass is constant, weight is not)
lift upward
normal force upward
basic physics states that the x-components and y-components of forces are independent. luckily for us, the force on the wing is a vector force, with a y-component acting in the upward direction.
at rest, the normal force equals the weight, because it is in equilibrium. for the wings to achieve lift, the thrust must be more than the drag, which it is, otherwise we wouldn't have mastered flight yet. this creates airflow over the wings, allowing the pressure to be less on the top, and more on the bottom. less pressure allows the plane to move upward. conversely, some race cars implement the same wings, but upside down to give it more downforce.
lift also must get to the point where is greater than the weight, because as the plane leaves the ground, the normal force no longer contributes to the system. this is achieved on a regular basis as all planes fly. as stated above, the y-component of the force of the wing becomes greater than the weight.
-----
under normal circumstances, the plane will be moving forward, so that the air flows over the wing.
Thrust > drag.
at rest, weight = normal force.
airborne, lift > weight.
during takeoff while still on the ground, lift and normal force = weight. the lift keeps increasing as the normal force continues to decrease.
ON THE TREADMILL
all of what i just stated works fine for typical takeoff. the treadmill makes things a little fuzzy. as aforementioned above, the bearings are frictionless and the wheels roll instead of sliding. the frictionless bearings allow the treadmill to match it's ground speed without any loss. so, the relative position, according to us, the bystander, is the same. the plane is not moving forward. the plane relative to the treadmill is different: it is moving relative to the belt position.
how is the plane staying on the treadmill and not moving backwards? the thrust generated by the engines. the thrust now is equal to the speed of it's wheels and treadmill, not necessarily overcoming drag like before.
the thrust force must translate to the speed of the wheels in order for the treadmill to keep it in place. this creates an interesting dynamic. is the ground speed the same as the airspeed? if so, half of you are right. if not, half of you are wrong. but i don't think this is the right question to be asking.
with that said, this could be rephrased to make even more sense and i think this is what we should have been asking in the first place. it becomes a question of relativity as much as airflow and airspeed. i take back my previous question at the top and replace it with this:
ARE THE WINGS MOVING RELATIVE TO THE SURROUNDING AIR?
i think that is the real question here. if the wings are, then the plane will have airspeed, and have airflow, and have lift on the wing surfaces. if not, the wings are in a stagnant surrounding of air with no airflow and no lift.
Here is my conclusion and I'm feeling pretty good about it:
Because the plane is moving relative to the treadmill, but not relative to the surrounding air, I support my previous answer with no, the plane will not take off. If you put the plane in a wind tunnel, the plane will have no problem getting airborne because it is moving relative to the air.
The air behaves similar to a fluid in that it is possible to have the air going through the engine, but not over the wings. This is why planes that have their brakes on with full thrust do not take off. Think about it this way: does a fan in your room move all of the air in one direction at that speed? No, it does not. It moves a localized amount of air to cool you off. There are gradients involved, and having the plane move down the runway allows the engines to pull the plane along so that the air can cover the entire wing surface.
Remember Me As A Time Of Day
If a treadmill was going the opposite way of the aircraft it would assist the aircraft on takeoff? Everyone knows how wheels turn it the treadmill is pushing this way -> and the aircraft is going this way <- its going to roll the wheels so they start moving forwards by themselves faster and faster until the aircraft take's off. However if the treadmill is going the same was as the aircraft its wheels will never move properly so it will never move properly.
For the 1st theory to work the aircraft has to be able to at least get 0.01 or so kmph and from there it will go up cause as the aircraft pushes forward the treadmill tries to counteract so it pushes it back even though youd probably burst the tires on takeoff its impossible to takeoff. They would pop and drop the aircraft it would be like landing an aircraft at 2X takeoff speed landings are normally done slower then takeoff cause more flaps are used. It would be performing a massive skid once it got enough speed like it was constantly landing until it got arbourne. Lets try this experiment out someone give me a vette we will buy a large treadmill and try to run the vette at 100kmph with the treadmill going 100kmph we will create airfoils on the vette and we will add in a F16 engine on the top.
This is a test that should be given to NASA or Mythbusters.
However if there is no air passing under the wings fast enough it wont takeoff.
For the 1st theory to work the aircraft has to be able to at least get 0.01 or so kmph and from there it will go up cause as the aircraft pushes forward the treadmill tries to counteract so it pushes it back even though youd probably burst the tires on takeoff its impossible to takeoff. They would pop and drop the aircraft it would be like landing an aircraft at 2X takeoff speed landings are normally done slower then takeoff cause more flaps are used. It would be performing a massive skid once it got enough speed like it was constantly landing until it got arbourne. Lets try this experiment out someone give me a vette we will buy a large treadmill and try to run the vette at 100kmph with the treadmill going 100kmph we will create airfoils on the vette and we will add in a F16 engine on the top.
This is a test that should be given to NASA or Mythbusters.
However if there is no air passing under the wings fast enough it wont takeoff.
Last edited by spray_and_pray (2006-12-27 10:44:09)
The arguments for both opions are good, I still think it would take off due to the tread mill not being able to overcome the thrust of 4 Pratt turbo fans, the tires are rated at quit a high speed for safety like Z-rated x4
Also think about the drag of the tread mill surface this will create a wind tunnel of it's own.
Lets say this 747 does not have wheels it hovers the tread mill should still have the same affect using the theorectical logic displayed here, in reality the plane would fall off the back of the tread mill before it could achieve enough airspeed to liftoff
Also think about the drag of the tread mill surface this will create a wind tunnel of it's own.
Lets say this 747 does not have wheels it hovers the tread mill should still have the same affect using the theorectical logic displayed here, in reality the plane would fall off the back of the tread mill before it could achieve enough airspeed to liftoff
Ballistics 101.
Providing the treadmill is fucking long, or the plane is fucking small, and the treadmill is going in the intended direction of travel of the aircraft:
1. Face plane on centre of (fucking long) treadmill.
2. Make the treadmill go fucking fast.
3. Plane will fly (briefly) off the end.
The distance travelled can be increased by putting the aforementioned (fucking long) treadmill on top of a cliff.
This method not only works for planes, but other items, such as toasters, cars, pensioners, wheelchairs and monkeys. Why not experiment with a combination of those?
Providing the treadmill is fucking long, or the plane is fucking small, and the treadmill is going in the intended direction of travel of the aircraft:
1. Face plane on centre of (fucking long) treadmill.
2. Make the treadmill go fucking fast.
3. Plane will fly (briefly) off the end.
The distance travelled can be increased by putting the aforementioned (fucking long) treadmill on top of a cliff.
This method not only works for planes, but other items, such as toasters, cars, pensioners, wheelchairs and monkeys. Why not experiment with a combination of those?
I didn't read the whole thread, but: http://answers.google.com/answers/threadview?id=428718
Party wrecker.
I have the PROOF!!!! I am editing the vid as we speak and will post it soon. I don't want to ruin the suprise so you will have to wait!!!viper313 wrote:
I have a friend that has a treadmill and I have a small electric plane. If some of you want I will test it and post a vid too prove either way.......
Well, mabey..... if the pilot is on crack.
Jesus Fucking Christ People. The Wheels Do Not Provide The Thrust. The Thrust Is Provided By The Humongous Jet Engines. The Minimal Amount Of Rolling Friction Caused On The Tired Would Have No Affect On The Planes Ability To Fly.
An airplane's lift is generated by air flow relative to the wings. The
speed of the aircraft relative to the runway is, in principle,
irrelevant.
In fact, let's put it this way: As long as the plane's wheels are
free to roll, the conveyor belt can move either forwards or backwards,
at any speed, but the engines will exert thrust and the aircraft will
aquire airspeed, and will liftoff regardless the belt.
speed of the aircraft relative to the runway is, in principle,
irrelevant.
In fact, let's put it this way: As long as the plane's wheels are
free to roll, the conveyor belt can move either forwards or backwards,
at any speed, but the engines will exert thrust and the aircraft will
aquire airspeed, and will liftoff regardless the belt.
You are one of the few people who understand how it works.norge wrote:
An airplane's lift is generated by air flow relative to the wings. The
speed of the aircraft relative to the runway is, in principle,
irrelevant.
In fact, let's put it this way: As long as the plane's wheels are
free to roll, the conveyor belt can move either forwards or backwards,
at any speed, but the engines will exert thrust and the aircraft will
aquire airspeed, and will liftoff regardless the belt.
My lord the question was already answered on digg.com
The plane will actually take off because the source of the aircraft's power is in the engines mounted on the wings.
Wheels only help with ground friction
The plane will actually take off because the source of the aircraft's power is in the engines mounted on the wings.
Wheels only help with ground friction
If it were a jet engine yes. For those who don't understand how a jet engine works, thrust is generated when the turbines suck cool air in. The cool air is super heated which causes it to expand which in turn generates thrust or propulsion. I would guess that even if the wheels were spinning there would be enough thrust eventually generated to create lift.
Xbone Stormsurgezz
Ok Ive not read the whole thread but I think I can say something :
At first I was telling to myself :"what a retard thread, no the plane would not take off, because it wouldnt be moving"
But I found myself a retard, when I read the example of a rollerblader attached to a rope at page 1
Finally, yes, the plane would take off, the plane being independant of the treadmill because of his engines. Yes there is something that connects it to the treadmill, but these are wheels, and they will only rotate at high speed, but not influence the planes speed.
Imagine something : your friend is running on a treadmill and the treadmill is set up the same way as the one of this thread. You are not on the treadmill, but firmly attached to the ground. You push your friend on his back, he will move forward with his legs running faster and faster. The only way he could stay at the same spot, would be if his legs didnt follow the speed of the treadmill. About the plane now, its the same thing, considering that the wheels can rotate at high speed without breaking down. And dont consider friction, its negligeable.
At first I was telling to myself :"what a retard thread, no the plane would not take off, because it wouldnt be moving"
But I found myself a retard, when I read the example of a rollerblader attached to a rope at page 1
Finally, yes, the plane would take off, the plane being independant of the treadmill because of his engines. Yes there is something that connects it to the treadmill, but these are wheels, and they will only rotate at high speed, but not influence the planes speed.
Imagine something : your friend is running on a treadmill and the treadmill is set up the same way as the one of this thread. You are not on the treadmill, but firmly attached to the ground. You push your friend on his back, he will move forward with his legs running faster and faster. The only way he could stay at the same spot, would be if his legs didnt follow the speed of the treadmill. About the plane now, its the same thing, considering that the wheels can rotate at high speed without breaking down. And dont consider friction, its negligeable.
Last edited by -=raska=- (2006-12-27 22:18:07)
Is it just me , or does that plane of yours look like this USS Monitor, which demonstrates that your illustration fails; clearly the Monitor has no good airfoil and could not achieve flight regardless of the friction or thrust.
Last edited by ATG (2006-12-27 22:33:32)
no no no no, if I'm not mistaken the thread said that the treadmill would be traveling at the same speed in the opposite direction so no matter how "fast" the plane would be moving on flat ground, it is not moving at anywhere because the forces going forward are the same as the forces going back...Kmarion wrote:
If it were a jet engine yes. For those who don't understand how a jet engine works, thrust is generated when the turbines suck cool air in. The cool air is super heated which causes it to expand which in turn generates thrust or propulsion. I would guess that even if the wheels were spinning there would be enough thrust eventually generated to create lift.
It does not fly, it just stays in the same place...
But the thrust of the jet would overpower the treadmill alowing forward movement.