lol this thread is still going?
no you wouldn't get any lift...
no you wouldn't get any lift...
Last edited by CommieChipmunk (2006-12-26 13:07:24)
OMG. If I could start flaming people and not get banned, I think I would. Instead, I would like to thank all the people who are supporting my answer.
All you people who say something about friction, you're crazy. Have you ever taken a physics class? Wheels create what is known as static friction. Basically (I'm not a physicist here, so I could use some help here) it means that the wheels have a constant grip on the ground and when a car's axle turns the wheel that grip pushes the car forward. When a car "peels out" it has overcome the static friction and the wheels are just sliding on the ground. In this scenario we are talking about a plane though. The friction between the wheels in the ground remains the same as it would regardless of the speed of the ground or treadmill. What the wheels do for the plane is negate the friction between the ground and the plane so that it can move forward when the engines provide thrust. The thrust does not come from the wheels moving. There is no axle tied between the jet and the wheels, nor are there any cables which make them spin. If you turned an airplane upside down and fire up the engines, the wheels probably wouldn't spin very much.
Up north I believe it is very common for a plane to take off on ice, they just have skis on them. This would be similar to your treadmill question in that the wheels wouldn't be useful (if you still believe the wheels are what makes a plane move forward then they would just slide on the ice.) Also, sea planes take off in water that is moving the other direction all the time... If you still believe a plane can not take off on a treadmill I'll get my professor / pilot dad to write a short paper about it and I'll post it on the internets.
Edit: I posted this without realizing there were more pages. I'm not changing anything though. For those of you who still believe the treadmill moving backwards prevents the plane from moving forwards: Please explain to me how the treadmill affects the air traveling through the jet / prop. The jet / prop pushes off the air (not the ground), which moves the plane forward, which moves the air past the wings (the forward motion moves the air past the wings, not the jet / prop), which creates lift, which makes planes fly. I would like to reiterate that the wheels simply allow a plane to easily slide across the ground and are not connected to any form of motion generating power.
I apologize for any double posting. Every time I delete the double it deletes both. Mods help please!
All you people who say something about friction, you're crazy. Have you ever taken a physics class? Wheels create what is known as static friction. Basically (I'm not a physicist here, so I could use some help here) it means that the wheels have a constant grip on the ground and when a car's axle turns the wheel that grip pushes the car forward. When a car "peels out" it has overcome the static friction and the wheels are just sliding on the ground. In this scenario we are talking about a plane though. The friction between the wheels in the ground remains the same as it would regardless of the speed of the ground or treadmill. What the wheels do for the plane is negate the friction between the ground and the plane so that it can move forward when the engines provide thrust. The thrust does not come from the wheels moving. There is no axle tied between the jet and the wheels, nor are there any cables which make them spin. If you turned an airplane upside down and fire up the engines, the wheels probably wouldn't spin very much.
Up north I believe it is very common for a plane to take off on ice, they just have skis on them. This would be similar to your treadmill question in that the wheels wouldn't be useful (if you still believe the wheels are what makes a plane move forward then they would just slide on the ice.) Also, sea planes take off in water that is moving the other direction all the time... If you still believe a plane can not take off on a treadmill I'll get my professor / pilot dad to write a short paper about it and I'll post it on the internets.
Edit: I posted this without realizing there were more pages. I'm not changing anything though. For those of you who still believe the treadmill moving backwards prevents the plane from moving forwards: Please explain to me how the treadmill affects the air traveling through the jet / prop. The jet / prop pushes off the air (not the ground), which moves the plane forward, which moves the air past the wings (the forward motion moves the air past the wings, not the jet / prop), which creates lift, which makes planes fly. I would like to reiterate that the wheels simply allow a plane to easily slide across the ground and are not connected to any form of motion generating power.
I apologize for any double posting. Every time I delete the double it deletes both. Mods help please!
Last edited by Krauser98 (2006-12-26 13:09:49)
Check what I wrote on the previous page (4) ...Krauser98 wrote:
If you still believe a plane can not take off on a treadmill I'll get my professor / pilot dad to write a short paper about it and I'll post it on the internets.
I apologize for any double posting. Every time I delete the double it deletes both. Mods help please!
I think your covered. But, I don't think your taking this subject seriously enough.Krauser98 wrote:
OMG. If I could start flaming people and not get banned, I think I would. Instead, I would like to thank all the people who are supporting my answer.
All you people who say something about friction, you're crazy. Have you ever taken a physics class? Wheels create what is known as static friction. Basically (I'm not a physicist here, so I could use some help here) it means that the wheels have a constant grip on the ground and when a car's axle turns the wheel that grip pushes the car forward. When a car "peels out" it has overcome the static friction and the wheels are just sliding on the ground. In this scenario we are talking about a plane though. The friction between the wheels in the ground remains the same as it would regardless of the speed of the ground or treadmill. What the wheels do for the plane is negate the friction between the ground and the plane so that it can move forward when the engines provide thrust. The thrust does not come from the wheels moving. There is no axle tied between the jet and the wheels, nor are there any cables which make them spin. If you turned an airplane upside down and fire up the engines, the wheels probably wouldn't spin very much.
Up north I believe it is very common for a plane to take off on ice, they just have skis on them. This would be similar to your treadmill question in that the wheels wouldn't be useful (if you still believe the wheels are what makes a plane move forward then they would just slide on the ice.) Also, sea planes take off in water that is moving the other direction all the time... If you still believe a plane can not take off on a treadmill I'll get my professor / pilot dad to write a short paper about it and I'll post it on the internets.
Edit: I posted this without realizing there were more pages. I'm not changing anything though. For those of you who still believe the treadmill moving backwards prevents the plane from moving forwards: Please explain to me how the treadmill affects the air traveling through the jet / prop. The jet / prop pushes off the air (not the ground), which moves the plane forward, which moves the air past the wings (the forward motion moves the air past the wings, not the jet / prop), which creates lift, which makes planes fly. I would like to reiterate that the wheels simply allow a plane to easily slide across the ground and are not connected to any form of motion generating power.
I apologize for any double posting. Every time I delete the double it deletes both. Mods help please!
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
Edit--> Also what will happen if it turns downriver and cuts off the engines
Last edited by JG1567JG (2006-12-26 13:31:29)
Like i wrote first..
-10mph down river ?
-10mph down river ?
Last edited by TPM-J45P3R- (2006-12-26 13:34:57)
That's not the same 'cos it doesn't have wheels that rotate ass fast as they want. That's like comparing car with round tires with a car with square tiresJG1567JG 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?
It would fall back to the river after almost taking offJG1567JG wrote:
Edit--> Also what will happen if it turns downriver and cuts off the engines
Last edited by tupla_s (2006-12-26 13:36:36)
The first question isn't the same but the same principle applies. The plane would float downriver backwards at 20mph.tupla_s wrote:
That's not the same 'cos it doesn't have wheels that rotate ass fast as they want like planes that take of from the groundJG1567JG 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 wind speed to get lift off. The planes max speed is 80mph. What will happen when the plane tries to take off?It would fall back to the river after almost taking offJG1567JG wrote:
Edit--> Also what will happen if it turns downriver and cuts off the engines
You are correct on the second even though a pilot could use the stick to create down force to create speed up to 100mph and then lift off and glide until the plane fell back to the river.
Last edited by JG1567JG (2006-12-26 13:41:44)
The wheels counteract any force that either the jets or the treadmill gives to the plane.
They allow both the plane and the treadmill to interact... So, for all of the energy the jets provide, that energy is displaced upon the movement of the wheels NOT HAVING STATIC FRICTION... because the treadmill is moving, thus, so are the wheels.
If the wheels were locked (not rotating) and the treadmill pushed the plane forward, fast enough, it could take off, just like a paper airplane.
If the treadmill were stopped, the planes jets would, of course, allow it to take off.
However, this interaction only forces the wheels to spin extremely fast... they would probably destroy themselves...
Also man... water in oceans or bays doesn't move... okay? The energy that we see in waves isn't actually the movement of water, but kinetic energy. Fill up a bowl with milk. put one cheerio in. tap the side of the bowl... Now, you will see waves, small ones. The cheerio won't follow the wave. It will move slightly... because the energy acts upon it... but it will not move, because the liquid isn't moving.
So no, planes do not take off on moving water. Unless it's a river... but they need enough speed to take off on a river... like they're pointing out...
another example: When running, you feel wind in your face, even if there's no wind. When running on a treadmill (outdoors, lets say), you only feel wind if wind is blowing at you. There is no air to provide upwards lift on the underside of a wing. This is what everyone else is saying, i know... but just use that as a more identifiable application of this theory.
They allow both the plane and the treadmill to interact... So, for all of the energy the jets provide, that energy is displaced upon the movement of the wheels NOT HAVING STATIC FRICTION... because the treadmill is moving, thus, so are the wheels.
If the wheels were locked (not rotating) and the treadmill pushed the plane forward, fast enough, it could take off, just like a paper airplane.
If the treadmill were stopped, the planes jets would, of course, allow it to take off.
However, this interaction only forces the wheels to spin extremely fast... they would probably destroy themselves...
Also man... water in oceans or bays doesn't move... okay? The energy that we see in waves isn't actually the movement of water, but kinetic energy. Fill up a bowl with milk. put one cheerio in. tap the side of the bowl... Now, you will see waves, small ones. The cheerio won't follow the wave. It will move slightly... because the energy acts upon it... but it will not move, because the liquid isn't moving.
So no, planes do not take off on moving water. Unless it's a river... but they need enough speed to take off on a river... like they're pointing out...
another example: When running, you feel wind in your face, even if there's no wind. When running on a treadmill (outdoors, lets say), you only feel wind if wind is blowing at you. There is no air to provide upwards lift on the underside of a wing. This is what everyone else is saying, i know... but just use that as a more identifiable application of this theory.
Last edited by djphetal (2006-12-26 13:45:35)
depends what the lift co-efficient of the plane wasJG1567JG wrote:
and glide untill the plane fell back to the river.
FredFLQ wrote:
QFTd3athwi5h4 wrote:
No, the plane being stationary wouldn't create any lift
Is this what you ment?TPM-J45P3R- wrote:
Like i wrote first..
If so look back another pageTPM-J45P3R- wrote:
A diagram to see if people understand,
http://www.qfom.com.au/images/how_wings.gif
To put it simple, there is NO airflow over the wing on a treadmill, the wheels are there only for movement on the ground. For the aircraft to takeoff the aircraft would have to equal the opposite force, and then over that speed to its Vr speed.
Eg: Treadmill @ 200mph opposite speed,
If the aircraft had a takeoff speed of say 200mph (no less),
Then for it to takeoff the aircraft would have to have a measured ground speed of 400mph, to counteract the movement of the 'ground'
Now I hope that makes some sense as I am half soaked
By the way we are in agreement on the question at hand.JG1567JG wrote:
I already said no on page 1 and I will explain why a little better.
If you have a plane/jet on the east end of a runway facing west. The runway acts as a large treadmill running in the opposite direction that the plane is going to take off. the runway itself moves from west to east and can match the planes speed and thrust. When the plane powers up the engines and the runway starts to move matching the planes speed, the plane would appear to sit still. The engines thrust would only stop it from going backwards off the runway.
Plane -->------>------>------> 300mph (wheelspeed because the plane would have no airspeed)
Runway <----<------<-----<-- 300mph
The plane wouldn't create any lift since the runway would counteract any speed the plane was able to create.
Now if the plane slowed to 200mph(wheel speed) and the runway stayed at 300mph the plane would go off the back of the runway.
If the plane would speed up to say 400mph (wheel speed) and the runway stayed at 300mph then the plane would move forward at 100mph (air speed). If the plane only needed 100mph to take off then it would.
Last edited by JG1567JG (2006-12-26 14:05:05)
He is absolutely correct. Like I said, it's all about airflow over the wings. Lift is created when air travelling over the top of the wing is forced to move faster than the air moving under the bottom of the wing (due to the curved upper surface). This creates an area of low pressure on top of the wing, which creates the lift. If the air isn't travelling fast enough you get no lift.......so like JG1567JG says, no airspeed=no lift.JG1567JG wrote:
I already said no on page 1 and I will explain why a little better.
If you have a plane/jet on the east end of a runway facing west. The runway acts as a large treadmill running in the opposite direction that the plane is going to take off. the runway itself moves from west to east and can match the planes speed and thrust. When the plane powers up the engines and the runway starts to move matching the planes speed, the plane would appear to sit still. The engines thrust would only stop it from going backwards off the runway.
Plane -->------>------>------> 300mph (wheelspeed because the plane would have no airspeed)
Runway <----<------<-----<-- 300mph
The plane wouldn't create any lift since the runway would counteract any speed the plane was able to create.
Now if the plane slowed to 200mph(wheel speed) and the runway stayed at 300mph the plane would go off the back of the runway.
If the plane would speed up to say 400mph (wheel speed) and the runway stayed at 300mph then the plane would move forward at 100mph (air speed). If the plane only needed 100mph to take off then it would.
ah you already wrote it!JG1567JG wrote:
Is this what you ment?TPM-J45P3R- wrote:
Like i wrote first..If so look back another pageTPM-J45P3R- wrote:
A diagram to see if people understand,
http://www.qfom.com.au/images/how_wings.gif
To put it simple, there is NO airflow over the wing on a treadmill, the wheels are there only for movement on the ground. For the aircraft to takeoff the aircraft would have to equal the opposite force, and then over that speed to its Vr speed.
Eg: Treadmill @ 200mph opposite speed,
If the aircraft had a takeoff speed of say 200mph (no less),
Then for it to takeoff the aircraft would have to have a measured ground speed of 400mph, to counteract the movement of the 'ground'
Now I hope that makes some sense as I am half soakedJG1567JG wrote:
I already said no on page 1 and I will explain why a little better.
If you have a plane/jet on the east end of a runway facing west. The runway acts as a large treadmill running in the opposite direction that the plane is going to take off. the runway itself moves from west to east and can match the planes speed and thrust. When the plane powers up the engines and the runway starts to move matching the planes speed, the plane would appear to sit still. The engines thrust would only stop it from going backwards off the runway.
Plane -->------>------>------> 300mph (wheelspeed because the plane would have no airspeed)
Runway <----<------<-----<-- 300mph
The plane wouldn't create any lift since the runway would counteract any speed the plane was able to create.
Now if the plane slowed to 200mph(wheel speed) and the runway stayed at 300mph the plane would go off the back of the runway.
If the plane would speed up to say 400mph (wheel speed) and the runway stayed at 300mph then the plane would move forward at 100mph (air speed). If the plane only needed 100mph to take off then it would.
|edit| - whoever +1 me didnt leave yer name!
Last edited by TPM-J45P3R- (2006-12-26 14:05:42)
It's all good just having fun +1 to youTPM-J45P3R- wrote:
ah you already wrote it!
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
This certainly IS an interesting topic. At first, I agreed with the crowd that said it would not take off. But after Krauser's post, I realized where my error was.
We all agree that the plane needs actual airflow over the wings to take off. No need to drag in pictures about how airflow over wings cause upward lift. What people are disagreeing about is that despite the backwatrds spinning of the wheels, a plane can still take off.
Lets say that the ratio of force to friction on tires is 1/100. That is, you need to have the treadmill go 100 MPH backwards to have it FEEL to someone holding the plane steady from OFF the treadmill of a 1MPH backwards force/
See, if a plane can take off at, say, 100 MPH, then the treadmill is running at that:
treadmill 100 MPH force <-<-<-<-
Now, if the plane was to get it's own FORWARD thrust up to 100 MPH:
forward thrust 100 MPH ->->->->
then it is getting a forward thrust of 100 and a backwards thrust of 1, so is going, relativley, 99.
We all agree that the plane needs actual airflow over the wings to take off. No need to drag in pictures about how airflow over wings cause upward lift. What people are disagreeing about is that despite the backwatrds spinning of the wheels, a plane can still take off.
Lets say that the ratio of force to friction on tires is 1/100. That is, you need to have the treadmill go 100 MPH backwards to have it FEEL to someone holding the plane steady from OFF the treadmill of a 1MPH backwards force/
See, if a plane can take off at, say, 100 MPH, then the treadmill is running at that:
treadmill 100 MPH force <-<-<-<-
Now, if the plane was to get it's own FORWARD thrust up to 100 MPH:
forward thrust 100 MPH ->->->->
then it is getting a forward thrust of 100 and a backwards thrust of 1, so is going, relativley, 99.
Last edited by [RDH]Warlord (2006-12-26 14:09:24)
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
It would still, technically, NOT take off since the relative forward thrust is still 99. If it were to take off, then the backwards thrust from the treadmill (which is, remember, only turns out to be 1 MPH) is gone and would keep itself afloat.
The treadmill would have to run at about 102 MPH (and the plane going 102) for it to take off. (102.00-001.02=100.08, more than the 100 it needs).
The treadmill would have to run at about 102 MPH (and the plane going 102) for it to take off. (102.00-001.02=100.08, more than the 100 it needs).
Last edited by [RDH]Warlord (2006-12-26 14:12:44)
Keep in mind that MY situation is theoretical. Nobody said that the treadmill is running at 100, and that the plane takes off at 100.
I could have done an example where the forward thrust is 200, the backwards is 200 (actual effect on the plane is 2), and it takes off at 100. Since it's thrust is 198, it'd definately take off.
I could have done an example where the forward thrust is 200, the backwards is 200 (actual effect on the plane is 2), and it takes off at 100. Since it's thrust is 198, it'd definately take off.
Now, I want to tackle this situation. Are we ignoring the fact that a floating plane would never go as fast as the river itself due to air friction? Are we assuming that all air above the river is standing rock still, not affected by the water below it?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
Anybody have a gas powered model plane and a treadmill. If I had the plane it would be on the tread mill right now. Not that I could duplicate this experiment the right way but it would be fun.
Last edited by JG1567JG (2006-12-26 14:22:17)
Wow just wow do you want to include the bird that is going to fly by causing an effect on the airflow and the fish that are swimming changing the current. I never said the plane would float at 100mph[RDH]Warlord wrote:
Now, I want to tackle this situation. Are we ignoring the fact that a floating plane would never go as fast as the river itself due to air friction? Are we assuming that all air above the river is standing rock still, not affected by the water below it?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.
Last edited by JG1567JG (2006-12-26 14:20:41)
Whew... all this is sooo much fun.... ATG must be falling outta his chair atm. I gotta send this question to my stoner buddies in college station.
I think Krauser is right. The energy/force created by the airflow thru the engine has very little interaction with the wheels. The engine will simply produce forward movement in the body of the jet. That energy is not transfered to the treadmill via the wheels.
I'm gonna hit up the Engineering squad at Texas A&M for this one.
KJ out.
I think Krauser is right. The energy/force created by the airflow thru the engine has very little interaction with the wheels. The engine will simply produce forward movement in the body of the jet. That energy is not transfered to the treadmill via the wheels.
I'm gonna hit up the Engineering squad at Texas A&M for this one.
KJ out.
krauser, i completely agree with you about the wheels. you are correct, they don't have anything to do with the plane moving forward, they merely reduce the friction and allow the plane to move forward.
i've looked this up and there are about 3500000000000000 threads about this.
from the arguements that i've read, both sides seem valid for different reasons. i need to think it through before i either support my argument or i support yours.
i'm leaving work right now, so i don't have time to go into it. i'll have to address this later, hopefully after a few force diagrams.
i've looked this up and there are about 3500000000000000 threads about this.
from the arguements that i've read, both sides seem valid for different reasons. i need to think it through before i either support my argument or i support yours.
i'm leaving work right now, so i don't have time to go into it. i'll have to address this later, hopefully after a few force diagrams.
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