Will the plane take off?

[pearl]

This is a big topic on Honda-tech, just wondering what you guys think about it.

If a plane is traveling at takeoff speed on a conveyor belt, and that conveyor belt is matching the speed in reverse, can the plane take off?

[Cardriverx]

yes, the plane is powered by jet engines pushing on the plane body, not spinning the wheels. The wheels would just be spinning double the rate of normal.

[whitezenki]

Blah, i voted no.

I'm wrong.

I have a plane, but never tried flyin it off a conveyor belt.

Quick thinking owns me.

[DropTopChevy]

This is already a thread like 2 years ago

[teh DIRT]

omg omg omg omg omg.

http://www.macguff.fr/goomi/unspeakable/WEBIMAGES/CARTOON/w003-repost.jpg

but since it is SOOO old, and some members probably weren't around for its torture...ENJOY!

[jspek]

^agreed.

[Renegade_]

This goddamn "riddle" doesn't go away does it? If someone doesn't get the right answer to this they are pretty dumb.

[DropTopChevy]

http://www.tristatetuners.com/forum/showthread.php?t=7435&
Found it.

[ITSTOCK]

Theoretically, yes, it could take off. It depends on the exact controlled variables.

[Renegade_]

When someone talks about speed it is always relative to the ground (earth), not the conveyor belt. There's a hint. High school physics teaches you this. The speed you might see on a hypothetical "speedometer" inside the airplane measures the speed of the wheels, not the plane itself.

[DropTopChevy]

No, with the conveyor keeping it in spot the plane will not recieve the amount of lift it would need at the speed in which it is capable of taking off at normally, if that makes sense.

Harrier Jet FTW.

[97TurboDSM]

holy super old topic

[Renegade_]

No, with the conveyor keeping it in spot the plane will not recieve the amount of lift it would need at the speed in which it is capable of taking off at normally, if that makes sense.

Harrier Jet FTW.
Thrust isn't the same as a car being propelled by traction. A car on a dyno stays still but a jet on a dyno wouldn't matter how fast the rollers move because the jet doesn't rely on the wheels to move it. The thrust would just move it forward. (I'm putting it in car terms :roll: )

The friction of the bearings in the wheels won't be enough to hold a jet back with the thousands of pounds of thrust it puts out. Then again if the jet were to reach takeoff speed the bearings in the wheels would just explode because of all the thousands of watts of energy it needs to displace.

So basically it won't take off because the wheels would just explode before any other variable could happen if the conveyor belt was keeping it still, but if it could move across the conveyor belt (like it should) then it "could" take off.

[pearl]

fair enough, lock it, its a repost. it is a great off topic discussion though.

[james_ls]

No.

Just cause.

[NJGOAT]

Yes it will take off as long as the wheels can spin as fast as they need to. Let's assume the jet powers up and starts moving forward at 1mph. The belt will then start moving 1mph in the opposite direction. Since the engines are pushing on the body of the plane and the wheels are simply there to hold up the plane and rotate freely, the wheels would be spinning forward at 2mph.

The problem with the whole riddle is that it isn't specific enough. If the conveyor matches the speed of the plane, then yes it will take off. However, if it is matching the speed of the wheels then the plane would never move and the wheels and conveyor would spin to infinite.

[wrx_snobordr]

Yes.

The wheels are only a way to decrease friction with the ground, not a means of producing propulsion. The wheels of the jet would simply be spinning at twice the air speed of the jet at take off. Think of it in reverse. If an F-18 was coming into land on an aircraft carrier and there was a conveyor belt spinning at the exact speed, but opposite direction of travel, to the jet would it stop dead if hitting a brick wall? NO, it would simply continue forward at a slightly slower speed, due to some resistance in a bearings, and if not caught by the cable it would go into the ocean.

[ITSTOCK]

^ thanks to the lift generated by its wings during its slow descent, of course......

[redline]

^ thanks to the lift generated by its wings during its slow descent, of course......

Yes it needs air flow across and under the wings to create low pressure and lift to fly, so NO the plane would not take off!

[pearl]

Yes it needs air flow across and under the wings to create low pressure and lift to fly, so NO the plane would not take off!
looks like this may be a good thread after all :)

[DropTopChevy]

Thrust isn't the same as a car being propelled by traction. A car on a dyno stays still but a jet on a dyno wouldn't matter how fast the rollers move because the jet doesn't rely on the wheels to move it. The thrust would just move it forward. (I'm putting it in car terms :roll: )

The friction of the bearings in the wheels won't be enough to hold a jet back with the thousands of pounds of thrust it puts out. Then again if the jet were to reach takeoff speed the bearings in the wheels would just explode because of all the thousands of watts of energy it needs to displace.

So basically it won't take off because the wheels would just explode before any other variable could happen if the conveyor belt was keeping it still, but if it could move across the conveyor belt (like it should) then it "could" take off.

I don't see how this relates to my post at all. Not once did I mention thrust, nowhere does the riddle say that it's a jet plane.:confused:

[whitezenki]

It will take off.

Speed is distance/time.

With a jet, the propulsion would push to body forward regardless of how fast the wheels are spinning.

The wheels are just bearings, there is no power too them, its the speed of the body of the plane that matters.

So if the plane is going at liftoff speed, it is, by definition, moving forward fast enough to create the necessary lift to take off.

The trick is to not think of it like a car. With a car the wheels are what drives the body, so a conveyor effect would reverse that energy.

A plane uses propulsion applied to the body, not the wheels. All it means is the wheels are gonna spin faster b/c of the conveyor, but the propulsion will still push the body forward at the speed needed to take off.

[whitezenki]

I don't see how this relates to my post at all. Not once did I mention thrust, nowhere does the riddle say that it's a jet plane.:confused:

Have you ever seen a plane powered by wheels? B/c it would have to be in order for the conveyor to counter the forward motion of the plane.

[pearl]

the plane will fly!

[redline]

the plane will fly!

So you meen to tell me the plane will be moving forward with its wheels spinning backwards at the same speed

[whitezenki]

Ughhh....

If a plane is using propulsion to attain any kind of speed, it will be moving forward.

If that speed is the equivalent of takeoff speed, it will fly.

The wheels will have to spin twice as fast as the speed of the plane b/c it is going against the conveyor belt as well, but that wont stop the plane from moving forward.

The speed of the wheels is INDEPENDENT of the speed of the plane.

[Zarno]

I'm taking physics right now in high school, so let's see how well my teacher is doing his job...

If the plane is moving at takeoff speed relative to the conveyor belt, but the conveyor belt is moving in the opposite direction at the same speed, then the net velocity of the plane relative to the air should be zero. And since velocity relative to the air is what matters when it comes to lift, it won't take off.

I guess we're assuming the thrust is only directed straight back and isn't pointed down or anything because this problem isn't fun with thrust vectoring.

[wrx_snobordr]

So you meen to tell me the plane will be moving forward with its wheels spinning backwards at the same speed

Airplane wheels have no drive line, they are simply a means of reducing friction for an easier take off. They spin freely and are not meant to inhibit forward motion of the body of the aircraft. The propulsion is generated by the jet engines thrusting against the air, not the ground. So yes, the wheels will be spinning at twice the aircraft speed and the jet will take off.

I'm taking physics right now in high school, so let's see how well my teacher is doing his job...

If the plane is moving at takeoff speed relative to the conveyor belt, but the conveyor belt is moving in the opposite direction at the same speed, then the net velocity of the plane relative to the air should be zero. And since velocity relative to the air is what matters when it comes to lift, it won't take off.

I guess we're assuming the thrust is only directed straight back and isn't pointed down or anything because this problem isn't fun with thrust vectoring.

Hes not doing his job. You are doing the same thing others are doing, focusing on the wheel speed and assuming that is responsible for airspeed. You could spin the conveyor belt at twice the speed of the aircraft and the only result will be wheels that are spinning three times faster than the airspeed of the aircraft, over the ground.

[Renegade_]

Hes not doing his job. You are doing the same thing others are doing, focusing on the wheel speed and assuming that is responsible for airspeed. You could spin the conveyor belt at twice the speed of the aircraft and the only result will be wheels that are spinning three times faster than the airspeed of the aircraft, over the ground.
Yeah, exactly.

You could make the airplane still and move a conveyor belt and the wheels would turn. But it would stand still. (well, in a frictionless environment but the principle is there) Speed is relative to the earth, not wheel rotation.

[Zarno]

Hes not doing his job. You are doing the same thing others are doing, focusing on the wheel speed and assuming that is responsible for airspeed. You could spin the conveyor belt at twice the speed of the aircraft and the only result will be wheels that are spinning three times faster than the airspeed of the aircraft, over the ground.

Are we both looking at this the same way? The way I see it, the plane is moving forward at takeoff speed relative to the conveyor belt and the belt is moving at the same speed in the opposite direction relative to the air/ground (assuming no wind) and taking the plane with it. So someone watching wouldn't see the plane moving forward at all, right?

I interpreted the problem as trying to say that the conveyor belt is influencing the motion of the plane rather than moving freely under the wheels without moving the plane at all.

[Renegade_]

Are we both looking at this the same way? The way I see it, the plane is moving forward at takeoff speed relative to the conveyor belt...
The conveyor belt doesn't have speed. The conveyor belt is standing still on the earth, it is just rotating surface for the wheels to spin on. Wheel RPM doesn't have any bearing on the speed of the airplane (speed being in relation to the earth).

I interpreted the problem as trying to say that the conveyor belt is influencing the motion of the plane rather than moving freely under the wheels without moving the plane at all.
As soon as the jets turn on, the thrust it makes would override any bearing friction the motion of the wheels would produce and then they would start turning in reverse while the plane moved forward.

[wrx_snobordr]

Are we both looking at this the same way? The way I see it, the plane is moving forward at takeoff speed relative to the conveyor belt and the belt is moving at the same speed in the opposite direction relative to the air/ground (assuming no wind) and taking the plane with it. So someone watching wouldn't see the plane moving forward at all, right?

I interpreted the problem as trying to say that the conveyor belt is influencing the motion of the plane rather than moving freely under the wheels without moving the plane at all.

If the plane used it wheels to propel itself along the ground in order to gain speed then your theory would be correct. However, planes are not propelled like a car so you can not think of it as one. You could seize all the bearings, turn on the jet engines and go to full power and the plane will skid down the runway and take off. All the conveyor belt is doing is doubling the wheel speed but having no effect on the relative motion, to a person standing at the side of the experiment, over the ground and more importantly through the air of the aircraft itself.

[Zarno]

The conveyor belt doesn't have speed.

But the surface of it has to have speed - the problem says it's moving in reverse at takeoff speed. So the surface of that conveyor belt is definitely moving with some speed.

If the plane used it wheels to propel itself along the ground in order to gain speed then your theory would be correct. However, planes are not propelled like a car so you can not think of it as one. You could seize all the bearings, turn on the jet engines and go to full power and the plane will skid down the runway and take off. All the conveyor belt is doing is doubling the wheel speed but having no effect on the relative motion, to a person standing at the side of the experiment, over the ground and more importantly through the air of the aircraft itself.

Again, I think the main thing here is whether you assume that the question says that the conveyor belt is moving the plane in reverse with it or if you're going to say that the wheels more or less spin freely and that the motion of the surface of the conveyor belt isn't moving the plane at all. I think it's up for grabs since it's not made clear.

[04 Turbo Spec]

The answer is NO.

First you need to understand the quesiton. The question is stating that the conveyor belt is moving at the planes take off speed in the opposite direction of the planes motion, therefore making the plane stationary with the wheels spinning at take off speed.


Since the jets/propellers on planes create a force called thrust to only push the plane so that ambient air in the atmosphere can rush over the wings, which in turn causes a negative pressure on the underside of the wings creating lift. BUT since the plane is on a conveyor belt the plane will be stationary; so there will be no air rushing over the wings there for no pressure difference on the wings and no lift.


and if you try to argue that if you were to use wing/nose mounted prop plane the answer will still be NO. the rushing air created by the props will provide the necessary wind speed to create lift. However the props are only creating a wind velocity great enough on a narrow portion of the wing(s); the ENTIRE surface of the wings need to be experiencing the sufficient wind velocity to create enough enough lift.

[Zarno]

It'd be nicer if the question clarified whether the plane is traveling at takeoff speed relative to the earth or relative to the surface of the conveyor belt that's underneath it. Without that, I think snobordr could be right... or me and Turbo... depending on how you read into it.

[DropTopChevy]

Have you ever seen a plane powered by wheels? B/c it would have to be in order for the conveyor to counter the forward motion of the plane.

Uh no? Where did You come up with an idea like that? Its all about air getting under the wings (lift) to get the plane off of the ground (to fly)

[whitezenki]

The answer is NO.

First you need to understand the quesiton. The question is stating that the conveyor belt is moving at the planes take off speed in the opposite direction of the planes motion, therefore making the plane stationary with the wheels spinning at take off speed.


Since the jets/propellers on planes create a force called thrust to only push the plane so that ambient air in the atmosphere can rush over the wings, which in turn causes a negative pressure on the underside of the wings creating lift. BUT since the plane is on a conveyor belt the plane will be stationary; so there will be no air rushing over the wings there for no pressure difference on the wings and no lift.


and if you try to argue that if you were to use wing/nose mounted prop plane the answer will still be NO. the rushing air created by the props will provide the necessary wind speed to create lift. However the props are only creating a wind velocity great enough on a narrow portion of the wing(s); the ENTIRE surface of the wings need to be experiencing the sufficient wind velocity to create enough enough lift.

Except planes dont measure speed at the wheels.

Ill say it again, THE SPEED THAT THE WHEELS ARE SPINNING IS INDEPENDENT OF THE SPEED OF THE PLANE.

The airplanes thrust has absolutely no effect on what happens at the conveyor belt, it effect the air. If air is going through the jets, or being pulled by a prop, the plane will move forward. All the wheels do is reduce/eliminate friction b/n the plane and whatever surface is below it.

[whitezenki]

I have an airplane, I fly it regularly during the summer.

I understand the concepts of lift, bernoulli's law etc..

If the plane's engine is pulling air through a jet or with a prop, the plane will move forward.

The wheels are freewheels with almost no friction, the conveyor belt therefore provides minimal force on the plane as a whole.

Takeoff speed is measured in airspeed, not groundspeed.

[wrx_snobordr]

Uh no? Where did You come up with an idea like that? Its all about air getting under the wings (lift) to get the plane off of the ground (to fly)

And it does that by pushing on the air, not the ground. Since the bearings in the wheels are supposed to be as frictionless as possible, they will spin freely at 2, 4, 10 or 100 times the standard ground take off speed while the aircraft gains the all important air speed smoothly and unimpeded.

[wrx_snobordr]

I have an airplane, I fly it regularly during the summer.

I understand the concepts of lift, bernoulli's law etc..

If the plane's engine is pulling air through a jet or with a prop, the plane will move forward.

The wheels are freewheels with almost no friction, the conveyor belt therefore provides minimal force on the plane as a whole.

Takeoff speed is measured in airspeed, not groundspeed.

Off topic, what kind of plane do you have? I just started towards my private, I am thinking I want to fly commercially, it is amazing! I fly again Friday and Saturday, weather permitting.

[Tiny]

looks like this may be a good thread after all :)

No, you fail.

Jets > Treadmill

As soon as they power up the jet gets pushed forward. Thread over and kill yourself.

[redline]

If the plane is sporting mods from Buschur and AMS then hell yes!

Since it is not and I still believe the plain to be standing still with tires spinning at the conveyor's speed, regaurdless if the wheels don't act on it the conveyor will, IDK after 2 40's of OLD E! I dont care anymore, Im getting primed.

[redline]

No, you fail.

Jets > Treadmill

As soon as they power up the jet gets pushed forward. Thread over and kill yourself.

Relax dude!

[horhay]

I understand the concepts of lift, bernoulli's law etc..


Thought it was Bernoulli's Principle...

Regardless, you're right. The thrust developed by the aircraft's propulsion system (jets, props, whatever) is SOMEWHAT independent of the conveyor. There would be enough friction (due to the weight of the aircraft and the contact area of the tires) to make takeoff more difficult, but the aircraft would eventually gain the speed needed.

The only way the answer to this question is no is if there is some word game going on.

[Tiny]

Relax dude!

NO YOU RELAX. I AM OG GOD DAMNIT AND THIS THREAD PISSES ME OFF SO I WILL VOICE MY DISPLEASURE BY YELLING AT YOU THROUGH THE COMPUTER

AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH

[whitezenki]

Off topic, what kind of plane do you have? I just started towards my private, I am thinking I want to fly commercially, it is amazing! I fly again Friday and Saturday, weather permitting.

Its a small ass ultralight.
http://i43.photobucket.com/albums/e373/xcusememisswyn/IMGP1295.jpg
My dad is a captain for NetJets, he flies private G4s. He got this for his days off, and since he is looking to retire soon.

My neighbor used to be a pilot trainer in the AF, he just bought a badass older prop plane to train his son on. I cant think of what it is right now, my Dad just flew to France or I'd call him and ask. lol

The guy has like 6 planes and his own runway and hangar. Pretty BA.




Apparently, Mythbusters will air this myth on Jan. 30.

Until then we got this guy:
http://www.youtube.com/watch?v=4owlyCOzDiE

[Vypurr]

http://wizbangblog.com/images/respect.jpg

[whitezenki]

Thought it was Bernoulli's Principle...

Regardless, you're right. The thrust developed by the aircraft's propulsion system (jets, props, whatever) is SOMEWHAT independent of the conveyor. There would be enough friction (due to the weight of the aircraft and the contact area of the tires) to make takeoff more difficult, but the aircraft would eventually gain the speed needed.

The only way the answer to this question is no is if there is some word game going on.

It is. I havent slept in 48 hours, stupid exams.

I read it like freshman year of HS anyway lol

[redline]

NO YOU RELAX. I AM OG GOD DAMNIT AND THIS THREAD PISSES ME OFF SO I WILL VOICE MY DISPLEASURE BY YELLING AT YOU THROUGH THE COMPUTER

AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH

Allright Jock! I hear ya.

[den9]

if the wind is blowing fast enough yes

[wrx_snobordr]

Its a small ass ultralight.
http://i43.photobucket.com/albums/e373/xcusememisswyn/IMGP1295.jpg
My dad is a captain for NetJets, he flies private G4s. He got this for his days off, and since he is looking to retire soon.

My neighbor used to be a pilot trainer in the AF, he just bought a badass older prop plane to train his son on. I cant think of what it is right now, my Dad just flew to France or I'd call him and ask. lol

The guy has like 6 planes and his own runway and hangar. Pretty BA.




Apparently, Mythbusters will air this myth on Jan. 30.

Until then we got this guy:
http://www.youtube.com/watch?v=4owlyCOzDiE

Nice! Looks fun to cruise around in. What are its stats?

Do you plan on flying for the airlines or just for fun?

[whitezenki]

Nice! Looks fun to cruise around in. What are its stats?

Do you plan on flying for the airlines or just for fun?

I'll ask my dad for the stats. Its an awesome plane, you see all kinds of crazy stuff with it, from animals to art on the farm fields and peoples trashy backyards.
This is my old HS from the window.
http://farm2.static.flickr.com/1037/992356703_ec11d9a045_b.jpg

Just for fun probably tho.
No reason why, just kind of never thought about it as a career.

[bastid]

The answer is no. The reason why is that the net acceleration of the plane is always zero relative to the not only the ground but more importantly the atmosphere. As the plane increases speed relative to the ground, the treadmill always compensates to fully negate any forward motion. Without forward motion, there is zero air moving past the wings.

The laws of gas pressure state that an object will move from a high pressure area to a low pressure area when the pressure difference is great enough to overcome the inertia/mass of the object. In this case, the object is a plane. Think of a curveball in baseball. The friction caused by the ball creates a pressure difference on one side and the ball "curves" toward the lower pressure zone. But if you spin a ball in place, it is not going to curve anywhere.

Because of the shape of the wing, air takes a longer amount of time to travel over the wing vs. under the wing. When the same amount of atmospheric gas travels a over different distances in equal time, the gas on the side of the wing that travels farther (top side of the wing) creates a lower pressure zone above the wing vs. below the wing. When the pressure difference is great enough (usually just over 200mph for a small/medium commercial flight), the plane itself travels toward the low pressure zone, or up. The only thing the jets do is bring the plane up to the proper speed relative to the air traveling past the wings to create lift.

I win.

/brain off

[foss]

I'm gonna ask my physics teacher lol.

[horhay]

Its a small ass ultralight.
http://i43.photobucket.com/albums/e373/xcusememisswyn/IMGP1295.jpg


Sweet, I play with the other end of the spectrum...

Old jet:
http://i19.photobucket.com/albums/b175/MrHorhay/AF%20Pics/IMG_5260.jpg

New jet:
http://www.skycontrol.net/UserFiles/Image/MilitaryAviation_img/200705/200705boeing-first-c17-dover-air-force.jpg

I'm not a pilot though, just a loadmaster, but I still get to (have to?) fly.

[wrx_snobordr]

To the OP, please put "to be answered January 30th" in the title.

For those of us who say it will take off, this is our day of vindication. ha ha

[whitezenki]

The answer is no. The reason why is that the net acceleration of the plane is always zero relative to the not only the ground but more importantly the atmosphere. As the plane increases speed relative to the ground, the treadmill always compensates to fully negate any forward motion. Without forward motion, there is zero air moving past the wings.

The laws of gas pressure state that an object will move from a high pressure area to a low pressure area when the pressure difference is great enough to overcome the inertia/mass of the object. In this case, the object is a plane. Think of a curveball in baseball. The friction caused by the ball creates a pressure difference on one side and the ball "curves" toward the lower pressure zone. But if you spin a ball in place, it is not going to curve anywhere.

Because of the shape of the wing, air takes a longer amount of time to travel over the wing vs. under the wing. When the same amount of atmospheric gas travels a over different distances in equal time, the gas on the side of the wing that travels farther (top side of the wing) creates a lower pressure zone above the wing vs. below the wing. When the pressure difference is great enough (usually just over 200mph for a small/medium commercial flight), the plane itself travels toward the low pressure zone, or up. The only thing the jets do is bring the plane up to the proper speed relative to the air traveling past the wings to create lift.

I win.

/brain off

You lose.

Thats under the assumption that takeoff speed is measured relative to the ground and wheel speed.

It isnt. Its measured in air speed. Every plane has a set air speed it needs to overcome in order to take off. The video i posted shows this, since the guy didnt have to increase the throttle on the plane as he increased the treadmill to well past the takeoff speed. Whether the treadmill was going 1mph or 15mph, it still took almost the same exact force (throttle, propulsion, whatever) for the plane to overcome the friction on the wheels and move forward on the treadmill.

The same exact idea would prove true on a conveyor belt the size of a runway.

Thanks for playing.

[wrx_snobordr]

Sweet, I play with the other end of the spectrum...

Old jet:
http://i19.photobucket.com/albums/b175/MrHorhay/AF%20Pics/IMG_5260.jpg

New jet:
http://www.skycontrol.net/UserFiles/Image/MilitaryAviation_img/200705/200705boeing-first-c17-dover-air-force.jpg

I'm not a pilot though, just a loadmaster, but I still get to (have to?) fly.

NICE! The inside of the C-5's are insane. I wouldn't mind flying around in either one of those all day.

[redline]

Sweet, I play with the other end of the spectrum...

Old jet:
http://i19.photobucket.com/albums/b175/MrHorhay/AF%20Pics/IMG_5260.jpg

New jet:
http://www.skycontrol.net/UserFiles/Image/MilitaryAviation_img/200705/200705boeing-first-c17-dover-air-force.jpg

I'm not a pilot though, just a loadmaster, but I still get to (have to?) fly.

Another AF guy, I didn't know. I hate Dover.

[Vypurr]

You lose.

Thats under the assumption that takeoff speed is measured relative to the ground and wheel speed.

It isnt. Its measured in air speed. Every plane has a set air speed it needs to overcome in order to take off. The video i posted shows this, since the guy didnt have to increase the throttle on the plane as he increased the treadmill to well past the takeoff speed. Whether the treadmill was going 1mph or 15mph, it still took almost the same exact force (throttle) for the plane to overcome the friction on the wheels and move forward on the treadmill.

The same exact idea would prove true on a conveyor belt the size of a runway.

Thanks for playing.
It wouldn't matter if the plane was on a conveyor belt the size of the runway or the size of the plane. It will not advance on the conveyor belt because the question assumes that the plane is already at takeoff speed on that belt. The plane is not accelerating, it is sitting at a steady speed. So the plane is moving at x mph in relation the the belt, but it is moving at 0 mph in relation to the ground. Unless it was moving at x mph in relation to the ground, there will not be airflow over the wings of the plane. If there is no airflow, there is no lift generated. if there is no lift, the plane will sit there at that speed no matter what.

[whitezenki]

Yah my dad used to fly c-5's and a bunch of other stuff for the AF.

He was a special ops pilot in Vietnam.

I guess I need to talk to him about all the **** he has done more often.

[redline]

It wouldn't matter if the plane was on a conveyor belt the size of the runway or the size of the plane. It will not advance on the conveyor belt because the question assumes that the plane is already at takeoff speed on that belt. The plane is not accelerating, it is sitting at a steady speed. So the plane is moving at x mph in relation the the belt, but it is moving at 0 mph in relation to the ground. Unless it was moving at x mph in relation to the ground, there will not be airflow over the wings of the plane. If there is no airflow, there is no lift generated. if there is no lift, the plane will sit there at that speed no matter what.

My point exactly and the wheels will be spinning the same speed as the conveyor due to the aircraft not moving.

[whitezenki]

It wouldn't matter if the plane was on a conveyor belt the size of the runway or the size of the plane. It will not advance on the conveyor belt because the question assumes that the plane is already at takeoff speed on that belt. The plane is not accelerating, it is sitting at a steady speed. So the plane is moving at x mph in relation the the belt, but it is moving at 0 mph in relation to the ground. Unless it was moving at x mph in relation to the ground, there will not be airflow over the wings of the plane. If there is no airflow, there is no lift generated. if there is no lift, the plane will sit there at that speed no matter what.

Takeoff speed is measured relative to airspeed, not the belt or the ground.

If the plane is AT takeoff speed it will, in theory of how takeoff speed is measured, have to be going forward with enough airflow to liftoff.

Technically, the plane isnt at takeoff speed until its speed relative to the air is great enough to take off.

It may mean it is going 2x the speed relative to the belt, but that is not how takeoff speed is measured.

It is not AT takeoff speed until it is cutting through the air at a speed great enough to create the lift to rise the plane.

[Tru2Blu]

too much brain usage to figure this out. i quit

[whitezenki]

Basically, a plane can not be at takeoff speed unless it is capable of taking off.

TECHNICALLY...

But if you want to measure the speed at the wheels rather than the airspeed, you are right, it would be stationary.

But the plane isnt at its real takeoff speed either.

[whitezenki]

But with that, I realize this is all we are gonna have:
http://lh3.google.com/rjc.uk.web/RctnGZLmr_I/AAAAAAAAAmY/H6gzvreWwvU/11.jpg?imgmax=512

Cant wait for the 30 of January.

Someone bump this at that time.

[bastid]

You contradict yourself. You state that a plane needs airspeed to take off and that, without it, it will not take off. Yet you state that it has enough airspeed to take off if it is staying still in relation to the atmosphere? **** the ground. It is sitting still and not moving forward through the air. The only thing that is providing an opposite force to the plane is the ground, and the opposite force on the wheels sure as **** won't make it fly.

I vote that it explodes on the runway.

[Blundetto]

nooo, the plane needs lift from wind in order to take off..if it has jet engines the plane will move faster, but so will the convayer belt..leaving the plane at a standstill with no wind to take off with.

[Raven18940]

What this is is a repost, we've had this discussion before, it goes nowhere. It's a freaking retarded question and a waste of TST's bandwidth.

[Raven18940]

nooo, the plane needs lift from wind in order to take off..if it has jet engines the plane will move faster, but so will the convayer belt..leaving the plane at a standstill with no wind to take off with.

The only force to slow the planes acceleration in this case is the friction of the wheel bearings, which is tiny. That conveyer belt is gonna have to move insane fast to generate enough friction in the bearings to counteract 2000lbs of jet thrust

[whitezenki]

The only force to slow the planes acceleration in this case is the friction of the wheel bearings, which is tiny. That conveyer belt is gonna have to move insane fast to generate enough friction in the bearings to counteract 2000lbs of jet thrust

and by insanely fast, its going to have to be alot faster than the 'takeoff speed' of the plane.

[Renegade_]

Think about it this way.

Just imagine a car in neutral on a conveyor belt. The belt starts moving, the tires spin backwards and the car starts sliding backward.

Now, keep the car in neutral but imagine that there are guys on either side of the car on the conveyor belt keeping the car in place. Now, when they start to walk forward the car moves with them but the wheels keep turning in reverse as it moves along the conveyor belt toward the end.

[whitezenki]

wooohooo...

takeoff speed in a windless world is measured in knots, which is speed relative to the ground.

You cant technically set a treadmill to knots.

And a plane that is stationary on a treadmill, no matter what speed it is rolling, is going at 0 knots.

so in order for a plane to be going at takeoff speed, it has to be going a certain speed relative to the ground, it cant be stationary

If a plane is going at take off speed, that means it is going at the amount of knots (speed relative to ground) which would create the force to liftoff.

but since you cant really set a treadmill to counteract this without removing the plane from its takeoff speed....


the problem is an impossible scenario

[horhay]

The question supposes the aircraft is at takeoff speed. That kind of negates all the conveyor talk. The aircraft is at takeoff speed, so yes, it can takeoff.

[whitezenki]

The question supposes the aircraft is at takeoff speed. That kind of negates all the conveyor talk. The aircraft is at takeoff speed, so yes, it can takeoff.

exactly.

You cant be at takeoff speed unless you can take off
lol

[bastid]

The question supposes the aircraft is at takeoff speed. That kind of negates all the conveyor talk. The aircraft is at takeoff speed, so yes, it can takeoff.

Take off speed in relativity to what???? There is no air traveling over or under the wings. It is the air pressure difference that causes lift. Not the speed of the wheels. No air traveling past the wings, no flight. I don't understand why this is so hard to comprehend. It's physics.

[redline]

exactly.

You cant be at takeoff speed unless you can take off
lol

Take off speed is going to mean much when outside sources are acting against it?

[Roto]

It'll take off and hit the roof and explode in flames since it's in a warehouse with some idiot who put the plane on the conveyor belt therefor it will take off and go nowhere.



blah

[Evo8kid]

how can it? its not moving forward, the wheels are just spinning, meaning there is not airflow which equals no lift.

[Chris215]

they have a preview on their site.
http://dsc.discovery.com/fansites/mythbusters/mythbusters.html

[bastid]

Alright, here are some actual facts:

My source is the Aeronautics Learning Laboratory for Science Technology and Research. They are funded by NASA, and the information on their website is indisputable.

THIS IS ALL YOU NEED TO KNOW ABOUT FLIGHT:

"Lift is produced by a lower pressure created on the upper surface of an airplane's wing compared to the pressure on the wing's lower surface, causing the wing to be "lifted" upward. The special shape of the airplane wing (airfoil) is designed so that air flowing over it will have to travel a greater distance faster, resulting in a lower pressure area (see illustration) thus lifting the wing upward. Lift is that force which opposes the force of gravity (or weight)."

Shape:
http://www.allstar.fiu.edu/aero/images/lift.gif

Resulting Pressure Difference:
http://www.allstar.fiu.edu/aero/images/lift-p.gif

Here's a little paintshop illustration of the problem at hand:

[Reiki]

But that doesn't actually help.
The problem is what is the speed of the airplane relative to?
If it is relative to air, it will fly.
If it is relative to the conveyor belt and so it is going at zero velocity relative to air, then it's not going to fly at that moment.
I haven't figured out what would happen if you increase the thrust yet...but that's the basic gist of the dispute...

I mean, the plane isn't taking off at time = 0 in the second case, but what happens if we add thrust? Then there will be lift, and when it overcomes the weight, then it will take off?

[bastid]

But that doesn't actually help.
The problem is what is the speed of the airplane relative to?
If it is relative to air, it will fly.
If it is relative to the conveyor belt and so it is going at zero velocity relative to air, then it's not going to fly at that moment.
I haven't figured out what would happen if you increase the thrust yet...but that's the basic gist of the dispute...

I mean, the plane isn't taking off at time = 0 in the second case, but what happens if we add thrust? Then there will be lift, and when it overcomes the weight, then it will take off?

You are on the right track, but not quite 100% correct. For all intents and purposes, there are two dimensions here (x and y). The opposite forces for X are drag and thrust. Drag is caused by the friction of the ground against the wheels (while grounded) and the air against the plane (in flight). The opposite forces for the Y dimension are gravity and lift. You can not use thrust perpendicular to the force of gravity to create lift.

[whitezenki]

Ugh...

Your cute drawing does a good job of explaining how a wing works.

But it doesnt tell how a plane can be at a takeoff speed if its velocity, its speed in knots, its speed relative to the ground, are all 0.

B/c it cant.

Takeoff speed isnt a specific number you can recreate and match on a treadmill.

It is a concept that involves a large physics equation, which in its simplest form, is speed relative to the still ground.

IF A PLANE IS ON A TREADMILL, NO MATTER THE SPEED THAT THE TREADMILL IS GOING, THE PLANE CAN NOT BE AT TAKEOFF SPEED IF IT IS STATIONARY RELATIVE TO THE GROUND.

Its wheels can roll at 1000mph, but if it doesnt have the forward momentum to create the air system your little drawing shows, it can not technically be at takeoff speed.

[pearl]

It will take off because the thrust of the motors would still push it forward, just the wheels would be moving twice as fast.

http://www.youtube.com/watch?v=4owlyCOzDiE

I heard that Mythbusters episode is on the 30th of January.

[Reiki]

Okay, after discussing this with my friends for a while and reading up on it online, I'm convinced (I could always be wrong) that I know the answer now.
Which, by the way, means that Zarno's physics teacher does a good job, but he just doesn't pay attention in class. =P

Okay. So here's the problem:
"If a plane is traveling at takeoff speed on a conveyor belt, and that conveyor belt is matching the speed in reverse, can the plane take off?"

So let's see...if an airplane is hovering over a conveyor belt and the conveyor belt is matching its speed, the airplane is flying right? It's not going to fall down because the conveyor belt is moving.

Alright, now put the wheels on the belt. Nothing has changed about the forces acting on the airplane. The thrust is still there from the engine, the lift is still being provided, but the wheels are just now touching the conveyor belt. Which, in the airplane's reference frame, is moving twice as fast as the takeoff speed, because the plane is moving takeoff speed forward, and the belt is moving takeoff speed backwards.

So as many people have already said, the plane is at takeoff speed relative to the air, the wheels are moving twice as fast, and the conveyor belt is just going along happily at takeoff speed, not affecting the airplane.

Now here's another problem that is along the same lines:
"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 the opposite direction). Can the plane take off?"

Now the thing is, if everyone thinks the airplane is stationary and therefore is not creating any lift, then wouldn't the conveyor belt be stationary too, since the airplane is stationary? =P Just an afterthought...

Okay. Now if the plane is moving at "takeoff speed" relative to the conveyor belt. Then it starts, at time = 0, at 0 velocity relative to the air. But as we know, the airplane has an engine, so once it turns on the engine, the airplane moves relative to the air, it doesn't care about what the wheels are doing.

[whitezenki]

My question is, if it was as simple as putting a plane on a machine similar to a treadmill then why wouldn't aircraft carriers implement that system rather then having to pick up enough speed not to just fall over the edge by using the makeshift runway?

You are still thinking in wheel speeds.

The plane needs to be moving forward relative to the ground(not the belt) in order for the it to be at takeoff speed.

This is made true by the definition of takeoff speed as speed relative to the ground. A plane on a treadmill going nowhere has a speed relative to the ground of 0 knots, and therefore not at takeoff speed.

Bastid has this idea that b/c he has a HS-level physics idea of how the wing works, it explains all the other factors of this problem.

If he would go look up takeoff speed, speed relative to ground, and implemented the idea of true airspeed as well as velocity into it, he would have a better understanding of how this works.

[bastid]

Ugh...

Your cute drawing does a good job of explaining how a wing works.

But it doesnt tell how a plane can be at a takeoff speed if its velocity, its speed in knots, its speed relative to the ground, are all 0.

B/c it cant.

Takeoff speed isnt a specific number you can recreate and match on a treadmill.

It is a concept that involves a large physics equation, which in its simplest form, is speed relative to the still ground. No forward momentum in relation to the atmosphere = no air pressure difference = no lift = no flight. We are in total agreement.

IF A PLANE IS ON A TREADMILL, NO MATTER THE SPEED THAT THE TREADMILL IS GOING, THE PLANE CAN NOT BE AT TAKEOFF SPEED IF IT IS STATIONARY RELATIVE TO THE GROUND.

Its wheels can roll at 1000mph, but if it doesnt have the forward momentum to create the air system your little drawing shows, it can not technically be at takeoff speed.

I explained the minimum amount of physics necessary to prove that it isn't going to take off :mrgreen: You are absolutely correct though.

To take your example to the next degree, aircraft carriers will often travel 30-40 knots into the wind so that the planes can take off with less of a runway.

[pearl]

watch the video, and then post a reply. explain why the plane moves forward then.

[Reiki]

I think the funny thing is that this is on a car forum.
So everyone thinks in terms of cars, rather than airplanes, that move forward in air, not on the ground on wheels. You can tell the difference by suspending a plane by a string and a car by a string.
A car suspended on a string would go nowhere, but a plane suspended on a string would still fly forward.

[foss]

YES IT WILL TAKE OFF.

The friction of the conveyer is equal to the WHEELS. The jets engines overpower the friction of the conveyer moving the plane foward, creating lift.

/thread.

[whitezenki]

Okay, after discussing this with my friends for a while and reading up on it online, I'm convinced (I could always be wrong) that I know the answer now.
Which, by the way, means that Zarno's physics teacher does a good job, but he just doesn't pay attention in class. =P

Okay. So here's the problem:
"If a plane is traveling at takeoff speed on a conveyor belt, and that conveyor belt is matching the speed in reverse, can the plane take off?"

So let's see...if an airplane is hovering over a conveyor belt and the conveyor belt is matching its speed, the airplane is flying right? It's not going to fall down because the conveyor belt is moving.

Alright, now put the wheels on the belt. Nothing has changed about the forces acting on the airplane. The thrust is still there from the engine, the lift is still being provided, but the wheels are just now touching the conveyor belt. Which, in the airplane's reference frame, is moving twice as fast as the takeoff speed, because the plane is moving takeoff speed forward, and the belt is moving takeoff speed backwards.

So as many people have already said, the plane is at takeoff speed relative to the air, the wheels are moving twice as fast, and the conveyor belt is just going along happily at takeoff speed, not affecting the airplane.

Basically, we have a conveyor belt of infinite length. We have a plane flying above it at whatever speed is required for takeoff, say 125mph. This speed will be relative to the ground, we havent even started the belt yet. At this speed the wings create just enough lift to take off and fly in a straight line.

Now start the belt in the opposite direction at 125 mph. Now the plane is at takeoff speed flying over the belt, but has not yet made contact with it. Both players are set at the speed of takeoff, they just need to be put together.

Lower the landing gear. It will make contact with the belt and begin to spin. If the belt were still the wheels would spin 125 mph, the speed of the plane relative to the ground. With the belt at 125mph, the wheels would spin at 250mph, but does that mean the plane immediately stops moving forward, and becomes stationary? Does all the lift disappear as soon the wheels make contact?

No. If that were the case, everytime a plane touched down it would come immediately to a complete stop.

The wheels will spin at 250mph, but the plane will still maintain its speed of 125 mph.

[whitezenki]

watch the video, and then post a reply. explain why the plane moves forward then.

I think the funny thing is that this is on a car forum.
So everyone thinks in terms of cars, rather than airplanes, that move forward in air, not on the ground on wheels. You can tell the difference by suspending a plane by a string and a car by a string.
A car suspended on a string would go nowhere, but a plane suspended on a string would still fly forward.

I know what article you read, very good point thou haha.

YES IT WILL TAKE OFF.

The friction of the conveyer is equal to the WHEELS. The jets engines overpower the friction of the conveyer moving the plane foward, creating lift.

/thread.

You guys are getting it.

[whitezenki]

I explained the minimum amount of physics necessary to prove that it isn't going to take off :mrgreen: You are absolutely correct though.

To take your example to the next degree, aircraft carriers will often travel 30-40 knots into the wind so that the planes can take off with less of a runway.

Exactly, they will in effect increase their true airspeed to get to their takeoff speed more easily.

Their wheels will be going a different speed than if that headwind were not there. But they will still attain their takeoff speed.

Getting to takeoff speed can be done in many ways...

but once you are there, you can take off.

If you can not take off, you arent at your takeoff speed.

That is the entire essence of the concept of takeoff speed.

It is the true airspeed required to take off. It is the point when the wind going over and under your wings is great enough to lift the plane.

[horhay]

Take off speed in relativity to what???? There is no air traveling over or under the wings. It is the air pressure difference that causes lift. Not the speed of the wheels. No air traveling past the wings, no flight. I don't understand why this is so hard to comprehend. It's physics.

With aircraft, takeoff speed is not relative to anything, it is the speed at which the wings generate enough lift to cause the aircraft to safely begin flight. No argument needed here. If the aircraft is at takeoff speed, it is able to take off.

Whats heavier, a ton of bricks or a ton of feathers?

[ITSTOCK]

I think that the confusion is coming from the treadmill vs conveyor, and what kind of conveyor belt.

Some of us are ASSuming that the conveyor belt is going to be matching the speed of the plane produced by the thrust. In the video posted above, the treadmill is NOT matching the speed of the plane, and the thrust is causing the plane to move faster than the treadmill.


Like I said, if the plane has enough directional thrust to take off without needing lift (like a rocket does, vertical), it's going to take off. However, if the plane needs lift to achieve take off, it needs to have an applied force to create lift. If there is no air moving to create lift, there is no flight.

[bastid]

With aircraft, takeoff speed is not relative to anything, it is the speed at which the wings generate enough lift to cause the aircraft to safely begin flight. No argument needed here. If the aircraft is at takeoff speed, it is able to take off.

Whats heavier, a ton of bricks or a ton of feathers?

The lift is caused by the air traveling opposite the wings. Forward thrust is negated entirely by the equally opposite traveling conveyor belt.

[whitezenki]

With aircraft, takeoff speed is not relative to anything, it is the speed at which the wings generate enough lift to cause the aircraft to safely begin flight. No argument needed here. If the aircraft is at takeoff speed, it is able to take off.

Whats heavier, a ton of bricks or a ton of feathers?

This is it.

This explains it all.

So much more simple than how I put it.

[turbo4g63]

i would say no...if the planes wheels are traveling say 150mph, and the belt is moving 150mph in the opposite direction the plane would be sitting still....take a treadmill for example...you are running 5mph, and the belt is moving the opposite direction at the same speed...you are no moving anywhere

[whitezenki]

The lift is caused by the air traveling opposite the wings. Forward thrust is negated entirely by the equally opposite traveling conveyor belt.

Your idea of forces sucks.

Forward thrust is on the air, while the conveyor belt acts solely on the wheels.

The wheels are an almost frictionless medium between the plane and whatever is below it.

In order for the miniscule friction of the wheels to negate the thrust of the engines, the conveyor belt would have to go at 1000343454.54x the speed of the engines.

[whitezenki]

True airspeed is the speed of an aircraft relative to the airmass in which it flies.

Takeoff speed is measured in true airspeed.

Thats why, as bastid said himself, a plane may fly into a headwind, to increase his true airspeed without increasing its speed across the ground.

If a plane is at its takeoff speed, the plane is going at a rate of speed relative to its surrounding airmass which would create lift, the speed of the wheels would mean nothing.

[foss]

i would say no...if the planes wheels are traveling say 150mph, and the belt is moving 150mph in the opposite direction the plane would be sitting still....take a treadmill for example...you are running 5mph, and the belt is moving the opposite direction at the same speed...you are no moving anywhere

Yes, you are confused. The friction created by the conveyor belt is at equilibrium with the wheels. An airplanes is not like a car; it is not driven by the wheels. The jet engine has enough force to move the plane forward on the conveyor. ASSuming that the conveyor is of infinite length, the plane will eventually gather enough lift for it to take off. Vulala!

[ITSTOCK]

Alright people, one more time....


Both sides can be right, and can be wrong.



If the "conveyor belt" is moving at the opposite direction and the same speed in which the THRUST is applied (force), the plane WILL NOT take off.

If the conveyor belt is moving at the same rate of the wheels (velocity), the plane WILL take off.


/THREAD NOW? Or define conveyor belt.

[whitezenki]

Alright people, one more time....


Both sides can be right, and can be wrong.



If the conveyor belt is moving at the opposite direction and the same speed in which the THRUST is applied (force), the plane WILL NOT take off.

If the conveyor belt is moving at the same rate of the wheels (velocity), the plane WILL take off.


/THREAD NOW?

The thing is the idea of the conveyor belt overcoming thrust does not at all pertain to takeoff speed, and is only imaginable at best.

The force of engine thrust(20,000 lbs?!?) would need to be negated by the friction created within the wheels. The friction of the wheels is so small, that the belt would need to move infinite times FASTER than the plane in order to offset the thrust of the engines.

Wheel Friction would have to be >= 20,000lbs of thrust. Not a chance, no way.

There is no way that the friction of the wheels is equal to or anywhere near the force of the engines thrust. You would have to move the conveyor belt at an enormous number of times faster than the plane speed in order for the wheel friction to become larger than the engines thrust.

[ITSTOCK]

The thing is the idea of the conveyor belt overcoming thrust does not at all pertain to takeoff speed, and is only imaginable at best..

The force of engine thrust(20,000 lbs?!?) would need to be negated by the friction created within the wheels. The friction of the wheels is so small, that the belt would need to move infinite times FASTER than the plane in order to offset the thrust of the engines.

Right, it's theoretical. I think that people were ASSuming that the "conveyor belt" (the hypothetical one) was matching the force generated by the thrust, not the ground speed of the plane.

The thrust generated by an engine forces air backwards, and this has no effect with the ground speed.

Conventional conveyor belt=plane takes off

Magic/hypothetical conveyor belt=plane doesn't take off

[whitezenki]

Right, it's theoretical. I think that people were ASSuming that the "conveyor belt" (the hypothetical one) was matching the force generated by the thrust, not the ground speed of the plane.

The thrust generated by an engine forces air backwards, and this has no effect with the ground speed.

Conventional conveyor belt=plane takes off

Magic/hypothetical conveyor belt at infinite times the planes speed=plane doesn't take off


lol, magic conveyor belt.
/thread

[ITSTOCK]

Well the question given was specific. Again, hypothetically speaking, you can have that situation. Actually creating it is a different story!

[whitezenki]

Well the question given was specific. Again, hypothetically speaking, you can have that situation. Actually creating it is a different story!

Yah, reading around on this, a lot of pilots felt that the wheels and landing gear would explode before the plane got to take off.

And that was only at double the takeoff speed, imagine what it would take to overcome the thrust of the engines as well.:bigeek:

[wrx_snobordr]

Right, it's theoretical. I think that people were ASSuming that the "conveyor belt" (the hypothetical one) was matching the force generated by the thrust, not the ground speed of the plane.

The thrust generated by an engine forces air backwards, and this has no effect with the ground speed.

Conventional conveyor belt=plane takes off

Magic/hypothetical conveyor belt=plane doesn't take off

If magical conveyor belt then magical frictionless bearings (operating at absolute zero) so the plane still takes off.

[bastid]

True airspeed is the speed of an aircraft relative to the airmass in which it flies.

Takeoff speed is measured in true airspeed.

Thats why, as bastid said himself, a plane may fly into a headwind, to increase his true airspeed without increasing its speed across the ground.

If a plane is at its takeoff speed, the plane is going at a rate of speed relative to its surrounding airmass which would create lift, the speed of the wheels would mean nothing.

I think we're arguing the same point from different angles. I think that the confusion here as mentioned by ITSTOCK is we don't know whether or not the plane is moving forward relative to the airmass. If plane is actually "gaining" on the conveyor belt at a rate greater than or equal to takeoff speed (relative to the airmass), it will take off. But if the plane is only traveling forward on the belt as if it were a treadmill, its travel in relation to its surrounding airmass is null.

My assumption after reading the problem was that the conveyor belt matched the thrust with an equal and opposite force, therefore negating any forward motion through the airmass. If I'm running on a treadmill on a handglider attached to me, I will not levitate once I hit a certain speed. Same principle applies to the plane unless I'm interpreting the problem incorrectly.

And as far as the personal attacks go on my understanding of physics, I could have easily majored in physics - in fact 2 of my professors through my undergrad attempted to recruit me. It was always one of my strongest subjects outside of my major, so I don't who you think you are to imply that my understanding "sucks," as you put it so eloquently.

[wrx_snobordr]

My assumption after reading the problem was that the conveyor belt increased in speed as the thrust forced the plane forward, therefore negating any forward motion through the airmass. If I'm running on a treadmill on a handglider attached to me, I will not levitate once I hit a certain speed. Same principle applies to the plane unless I'm interpreting the problem incorrectly.


This is where everone is going wrong. A jets wheels are not like your feet or a cars wheels. They are independent. Your feet can only move as fast as your body will allow. A jets wheels are nothing more than friction reduction devices.

Take your same example but put on rollerblades. Stand there and start the tread mill, hold yourself in place. You can crank the treadmill up to 120mph and you will not need to apply any more force to keep yourself stationary because the wheels are doing their job, they are limiting the friction between the bottom of your feet and the treadmill. Now, strap a jet engine onto your back and fire that bitch up. You WILL accelerate forward relative to a person standing still on the side of you. You WILL reach a proper airspeed needed for take off. You r wheels WILL be going 120+ take off speed at the instant before you lift off. Then your airborne and we will blow that damn treadmill up and let this damn thread go.

[whitezenki]

I think we're arguing the same point from different angles. I think that the confusion here as mentioned by ITSTOCK is we don't know whether or not the plane is moving forward relative to the airmass. If plane is actually "gaining" on the conveyor belt at a rate greater than or equal to takeoff speed (relative to the airmass), it will take off. But if the plane is only traveling forward on the belt as if it were a treadmill, its travel in relation to its surrounding airmass is null.

My assumption after reading the problem was that the conveyor belt increased in speed as the thrust forced the plane forward, therefore negating any forward motion through the airmass. If I'm running on a treadmill on a handglider attached to me, I will not levitate once I hit a certain speed. Same principle applies to the plane unless I'm interpreting the problem incorrectly.

And as far as the personal attacks go on my understanding of physics, I could have easily majored in physics - in fact 2 of my professors through my undergrad attempted to recruit me. It was always one of my strongest subjects outside of my major, so I don't who you think you are to imply that my understanding "sucks," as you put it so eloquently.

because im an asshole, and its the internet.

I could go on and on about my physics knowledge, math skills, etc.

But i dont care enough too.

And a major point of the arguement is that takeoff speed is measured in relation to surrounding airmass, not wheel speed or ground speed.

The last two pages has been me trying to explain that.

You didnt help with your immediate "I Win" attitude.

And when it comes down to it, I'm just a 20 y/o kid. Anyone who gets upset with what i say shouldnt, b/c if I may seem to be a dick here, but in the next thread I might be cool.

If I met you tommorow, I would shake your hand and look you in the eye and be cool.

In other words, its the internet, dont take me seriously.

And I havent slept in 48 hours, boo exams.

I'm grumpy.

[pearl]

zenki, watch the video i posted. and reply to me.

[whitezenki]

Pearl.

See the bottom of this post:
http://www.tristatetuners.com/forum/showpost.php?p=759001&postcount=46

But you get an A for effort:wink:

[pearl]

i looked at it, but it doesnt answer why the plane on the treadmill, even at 10mph, with the same throttle amount that is pressed at 2mph, sits at the same spot on the treadmill. once full throttle is applied and it overcomes the friction of the wheels spinning twice as fast as the MPH,

it will take off!

[whitezenki]

The idea of the video is to show that the wheel friction is minimal in comparison to the thrust of the plane.

The wheels can spin at any speed, but 99.5% of the what the plane does is decided by the thrust.

[pearl]

i think that the video shows that the plane can still produce thrust on the treadmill.

[ITSTOCK]

OR everyone can think of it this way...

ASSuming a conventional conveyor belt :lol: ....


Can a plane take off on water? Can a plane take off in snow? Does the plane use wheels for either of these?

[bastid]

I see the point that if there's an amount of thrust that can push the plane forward independent of the wheels, it will take off. My impression of the problem was that the thrust would only match the opposite force of friction upon the wheels. The rollerblade analogy was a good one, but without a jet, you wouldn't be able to let go without falling off the back of the treadmill. I would argue the same goes for a plane, which has an immense amount of mass on each wheel.

Obviously the mass is small compared to the power of the jet, but if the jet's thrust was only enough to equal the opposite friction (which is how I interpreted the problem originally), the plane won't fly. Now, if they WOT that bitch, yes it will fly.

For a lot of us, we're arguing answers that are all correct based on different interpretations of the problem.

[dragonfly2k3]

I refuse to read all of this.
Anyways, is the conveyor belt just moving the wheels backwards? or are we trying to say that the plane is at a standstill compared to its airmass? If the plane is not moving relative to its surrounding airmass then no flight. The aircraft requires airflow over the wings to create lift(as air moves over the wing the design of the wing requires the air going over the top to move faster creating a low pressure area so that the higher pressure air below the wing can push the aircraft up) I caught a few glimpses, is this question trying to say that the conveyor belt is keeping the plane in place even at take-off throttle(full)? There is no possible way. In real life it wouldnt really matter how fast the conveyor belt is moving in the opposite direction, the plane would take off.

[Uberu]

I can end this dumb discussion right here. My dad is a pilot for continental airlines and has been for 30 years so he has been reading this thread. The answer is a very definitive NO. There are no buts to this, it will not take off unless its relative airspeed is sufficient for lift. So, if the conveyor is moving backwards at the same rate the jet is moving "fowards" then the relative airspeed is ZEROOOOO which definitely will not take off. THERE IS ABSOLUTELY NO ARGUING THIS BECAUSE NONE OF YOU A) HAVE OVER 40 YEARS OF FLYING EXPERIENCE B)OR TRULY KNOW HOW FLYING WORKS. Sorry to sound like a dick but this is the second time this thread has been around and people just don't get it

[ITSTOCK]

I can end this dumb discussion right here. My dad is a pilot for continental airlines and has been for 30 years so he has been reading this thread. The answer is a very definitive NO. There are no buts to this, it will not take off unless its relative airspeed is sufficient for lift. So, if the conveyor is moving backwards at the same rate the jet is moving "fowards" then the relative airspeed is ZEROOOOO which definitely will not take off. THERE IS ABSOLUTELY NO ARGUING THIS BECAUSE NONE OF YOU A) HAVE OVER 40 YEARS OF FLYING EXPERIENCE B)OR TRULY KNOW HOW FLYING WORKS. Sorry to sound like a dick but this is the second time this thread has been around and people just don't get it

LOL

Your dad should stick to flying the plane (or at least read what is going on).

Read below...

Both sides can be right, and can be wrong.



If the "conveyor belt" is moving at the opposite direction and the same speed and EQUAL FORCE in which the THRUST is applied (force), the plane WILL NOT take off.

If the conveyor belt is moving at the same rate of the wheels (velocity), the plane WILL take off.


/THREAD NOW? Or define conveyor belt.

Right, it's theoretical. I think that people were ASSuming that the "conveyor belt" (the hypothetical one) was matching the force generated by the thrust, not the ground speed of the plane.

The thrust generated by an engine forces air backwards, and this has no effect with the ground speed.

Conventional conveyor belt=plane takes off

Magic/hypothetical conveyor belt=plane doesn't take off

The wheels aren't the driving force, the thrust produced by the engine pushing air backwards is what is making the plane move. Therefore, the plan is going to move no matter what the wheels are doing.

Go create a magic conveyor belt that matches the force of applied thrust, and we'll stick with your theory. Otherwise, in the real world, with real conveyor belts, the plane takes off.

In your dads theoretical situation, you are right. But you can't really duplicate that test on a large scale, since well, you just can't!

[whitezenki]

lol....


hahahahahaha
hahahahahahahahha
hahahahahhahahahahahahaha





haahhahahaha
hahahahahahahahahaha






http://www.bjacked.net/LuvToHunt/forums/phpBB2/modules/gallery/albums/album01/Beat_Dead_Horse.jpg


And he obviously didnt read the whole thread.

It all depends on how you view it.

If you view it in technical takeoff speed, you can, if you view it by wheel speed, you cant.

go ask your dad how they measure speed.

[Uberu]

It should be modified to say that, "If a conveyor belt was able to move at the same speed that the plane would have to reach for take off, then it would be impossible to take off. However, if the conveyor belt couldn't match the speed, then obviously it could take off. The question is a little ambiguous in the first place but my interpretation (as well as my dad's) was that the conveyor belt matched the speed needed for the plane to take off and the answer would be a definite NO

[ITSTOCK]

EDIT!

But seriously, if given a question on a test, what kind of answer do you usually give? The REALISTIC solution to the given problem, or the magical one in which the device could only ever exist on paper?

[whitezenki]

We already established that.
http://www.bgstudios.com/images/YoureLate.jpg

[pearl]

I can end this dumb discussion right here. My dad is a pilot for continental airlines and has been for 30 years so he has been reading this thread.
LOL
Let me know what flights your father flies, as I would not fly with him.


Honestly, this pretty much sums it up, and I agree 100% with whoever said this:
If the "conveyor belt" is moving at the opposite direction and the same speed and EQUAL FORCE in which the THRUST is applied (force), the plane WILL NOT take off.

If the conveyor belt is moving at the same rate of the wheels (velocity), the plane WILL take off

What I believe is highlighted in bold. The belt matches the speed at take off, period.

That is all the riddle says, it does NOT say that the belt will speed up as the plane moves faster. Even if it did, the planes thrust WILL overcome the belt and propel itself forward).

[dragonfly2k3]

On a side note SMGsub. I describe in the post before yours exactly how flight works. lol. I, as well, would not fly with your father. While I think that the original question was trying to say the aircraft is at a stand-still I think we all can see that is impossible. There is not nearly enough friction in those wheels to stop the aircraft, if there was, landing would be terrifying.

[wrx_snobordr]

I do not get all of this different meanings discussion. If the plane is sitting still the convener belt does not move, for every MPH froward the plane moves the convener moves the exact same speed in the opposite direction. The conveyor belt could not impart an equal force on the plane because it is not in direct contact with the plane. As has been said multiple times all the conveyor belt can do is match the velocity of the wheels, which since their entire reason for existence is to reduce friction, means that they will not inhibit the plane from taking off whatsoever. The only real result will be wheels that are spinning twice as fast in MPH as the planes air speed. Stop over thinking this, its really pretty basic.

[NJGOAT]

I explained this in my original post on page 1. There are two answers to the riddle depending on how you interpret it. The above posts are right in that statement, but wrong on which way it will or won't take off.

Scenario 1: The conveyor matches the speed of the plane. In this scenario, the plane will take off. The engines throttle up sufficiently enough to move the plane 1mph. The conveyor begins to move 1mph in the opposite direction. The wheels will move 2mph forward. This will continue until the plane reaches take off speed. Let's assume that speed is 350mph. The planes air speed will be 350mph, the conveyer will be moving 350mph in the opposite direction and the wheels will be spinning 700 mph forward. This is the example that is proven in the roller skates on the treadmill example.

Scenario 2: The conveyor matches the speed of the wheels. In this scenario, the plane will not take off. The egnines power up to begin moving the plane 1mph forward. The conveyor matches the wheel speed 1mph in the opposite direction. The wheels can never exceed the speed of the conveyor as in scenario 1 as they constantly cancel each other out. The jet would sit there engines screaming as the wheel and conveyor would cancel each other out until infinite.

It all depends on how you interpret the meaning of the riddle and why it is BS. There is simply not enough information to give a definitive answer.

[wrx_snobordr]

I explained this in my original post on page 1. There are two answers to the riddle depending on how you interpret it. The above posts are right in that statement, but wrong on which way it will or won't take off.

Scenario 1: The conveyor matches the speed of the plane. In this scenario, the plane will take off. The engines throttle up sufficiently enough to move the plane 1mph. The conveyor begins to move 1mph in the opposite direction. The wheels will move 2mph forward. This will continue until the plane reaches take off speed. Let's assume that speed is 350mph. The planes air speed will be 350mph, the conveyer will be moving 350mph in the opposite direction and the wheels will be spinning 700 mph forward. This is the example that is proven in the roller skates on the treadmill example.

Scenario 2: The conveyor matches the speed of the wheels. In this scenario, the plane will not take off. The egnines power up to begin moving the plane 1mph forward. The conveyor matches the wheel speed 1mph in the opposite direction. The wheels can never exceed the speed of the conveyor as in scenario 1 as they constantly cancel each other out. The jet would sit there engines screaming as the wheel and conveyor would cancel each other out until infinite.

It all depends on how you interpret the meaning of the riddle and why it is BS. There is simply not enough information to give a definitive answer.

Your answer 1 is the same as answer 2. in both of them the wheels speed is being canceled. I can't figure out the reasoning behind why in 1 the jets body moves forward and in 2 it stays stationary. This was the reasoning for my post above, I feel people are over thinking this.

[Scapegoat]

someone write the goddamn mythbusters about this and get this **** over with

edit: ****it, I'll do it myself...

[Scapegoat]

nevermind, someone beat me to it on their forum :)

http://community.discovery.com/eve/forums/a/tpc/f/9551919888/m/2211983939

[pearl]

the main point is that the treadmill WILL NOT keep the plane stationary.
the treadmill only keeps the speed of TAKEOFF, nothing else.

[whitezenki]

nevermind, someone beat me to it on their forum :)

http://community.discovery.com/eve/forums/a/tpc/f/9551919888/m/2211983939

They have an episode for it already.

Its gonnna air on Jan. 30th.

[NJGOAT]

Your answer 1 is the same as answer 2. in both of them the wheels speed is being canceled. I can't figure out the reasoning behind why in 1 the jets body moves forward and in 2 it stays stationary. This was the reasoning for my post above, I feel people are over thinking this.

As someone stated earlier, air speed is the key to the plane. If the conveyor is acting upon the "planes" forward motion, than the wheels will simply spin faster since the plane is forcing them to move. The conveyor in this scenario cannot cancel out the planes forward movement as the wheels are a non-factor.

In the second scenario the conveyor is acting directly against the "wheels" speed. This will cancel out any forward movement into infinite.

The key is which speed the conveyor is matching. The plane HAS to move forward to gain velocity for take off. That means that from a stationary position the wheels must gain forward momentum. Scenario one has the wheel as a non-factor where it simply spins as fast as is needed to accomodate both forces acting on it. Scenario two negates the forward movement of the wheel as the conveyor is matching the wheel speed. Scenario 2 is the most unrealistic as the end sum would be infinite, where as in Scenerio 1 if we knew all the force numbers we could calculate when the plane would take off.

[pearl]

i will be watching it.

[thewake]

I explained this in my original post on page 1. There are two answers to the riddle depending on how you interpret it. The above posts are right in that statement, but wrong on which way it will or won't take off.

Scenario 1: The conveyor matches the speed of the plane. In this scenario, the plane will take off. The engines throttle up sufficiently enough to move the plane 1mph. The conveyor begins to move 1mph in the opposite direction. The wheels will move 2mph forward. This will continue until the plane reaches take off speed. Let's assume that speed is 350mph. The planes air speed will be 350mph, the conveyer will be moving 350mph in the opposite direction and the wheels will be spinning 700 mph forward. This is the example that is proven in the roller skates on the treadmill example.

Scenario 2: The conveyor matches the speed of the wheels. In this scenario, the plane will not take off. The egnines power up to begin moving the plane 1mph forward. The conveyor matches the wheel speed 1mph in the opposite direction. The wheels can never exceed the speed of the conveyor as in scenario 1 as they constantly cancel each other out. The jet would sit there engines screaming as the wheel and conveyor would cancel each other out until infinite.

It all depends on how you interpret the meaning of the riddle and why it is BS. There is simply not enough information to give a definitive answer.

If a plane is traveling at takeoff speed on a conveyor belt, and that conveyor belt is matching the speed in reverse, can the plane take off?

1. What has a speed? The plane.
2. The conveyor matches what? The speed of the plane.

Scenario 1: check
Scenario 2: wheels? who said anything about wheels? only the speed of the plane is relevant to the question.

The question is not ambigous, measuring speed at the wheels is a meme (http://dictionary.reference.com/browse/meme) of the automotive culture. It is not valid here. Break away from your preconceptions and actually answer the question as is is asked. This is the reason why this is driving car forums crazy.

[Renegade_]

The plane has inertia and the wheels have rotational velocity. Are you telling me the rotational velocity of the wheels and the friction of the bearings will overpower the inertia a plane gains when hundreds of thousands of pounds of thrust are applied?

This is what everyone is saying when they say the plane doesn't move. Think about it.

I'm gonna stop posting here because everyone comes in with self righteous indignation about their side. Stop thinking in terms of cars people. The wheels are nothing in this equation. Think about a shopping cart on a conveyor belt.

You can hold it still right? You can also pull it forward and back across the conveyor belt right? No matter how fast the conveyor belt moves, you can still move it forward and back. Same with a jet, except the jet has it's own power source and will move forward of its own free will. Lets say the conveyor belt is moving at 100mph. Lets say you are strong enough to hold it still. If you provide just a tad more force the shopping cart will move forward even if the conveyor belt is moving at 100mph (this is given that the bearings can handle this)

Here's another example. Say you have a Radio flyer on a conveyor belt and attached to it is a huge mast with a sail. Lets say there is a lot of wind coming in and when the cart starts moving the conveyor belt starts moving. Your telling me that the force the conveyor belt exerts on the object will be strong enough to hold it back?

*edit* Thought of a better idea.

Think of it in terms of a hydrofoil. There is friction from the contact with the water. If a hydrofoil moves at 1mph and the water moves at 1mph, do you think this will stop it? Nope. Same with 2, 3, 5, 6, etc etc mph... If a hydrofoil moves upstream at 10 knots and the water comes back at 10 knots, is it going to stand still? Hell no. The principle is exactly the same, just people need to stop thinking that the wheels are the indicator of whether or not it stands still.

*edit 2* If the conveyor belt stands still and just spins, the airplane will take off. See above for explanation.

If the conveyor belt moves with the airplane (like a conveyor belt on a conveyor belt) it doesn't matter if the wheels spin or not when it reaches takeoff velocity.

[NJGOAT]

1. What has a speed? The plane.
2. The conveyor matches what? The speed of the plane.

Scenario 1: check
Scenario 2: wheels? who said anything about wheels? only the speed of the plane is relevant to the question.

The question is not ambigous, measuring speed at the wheels is a meme (http://dictionary.reference.com/browse/meme) of the automotive culture. It is not valid here. Break away from your preconceptions and actually answer the question as is is asked. This is the reason why this is driving car forums crazy.

We are essentially in agreement. I was attempting to point out why people have such a hard time with this. Yes, the wheels do in fact have a speed. For scenario 1 to be true and we know it is, the wheels must spin forward at the rate the plane is pushing them plus the speed of the conveyor belt that is going in reverse. For example: X=the speed of the plane. Y=the speed of the conveyor. Z=the speed of the wheels. If Y=X then the plane will take off, if Y=Z then it won't.

In scenrio 1 - X+Y=Z

In scenario 2 - Y=Z and X=0

[Renegade_]

Speed of wheels has jack to do with this short of figuring out how much resistance you should factor in with the bearings.

[thewake]

We are essentially in agreement. I was attempting to point out why people have such a hard time with this. Yes, the wheels do in fact have a speed. For scenario 1 to be true and we know it is, the wheels must spin forward at the rate the plane is pushing them plus the speed of the conveyor belt that is going in reverse. For example: X=the speed of the plane. Y=the speed of the conveyor. Z=the speed of the wheels. If Y=X then the plane will take off, if Y=Z then it won't.

In scenrio 1 - X+Y=Z

In scenario 2 - Y=Z and X=0

The question defines Y=X so in scenario 2 X=0, Y=0, Z=0, no movement of anything, but it also defines X as a non-zero value. This is an invalid scenario. Unless the wording of the question is changed there is ONLY scenario 1.

[dragonfly2k3]

this argument is beat to death. In a real world situation the plane would take off.
Lets say you have a jet on the deck of an aircraft carrier pointing east, the carrier is moving west at the planes take off speed, you now increase the aircrafts speed to take off speed, the aircraft will still take off. The only downfall to this situation is how quickly you would have to get the aircraft up to take off speed before it fell off the end of the carrier. I know it is impossible for a carrier to move that fast but i think this gives everybody a mental picture.

[sherwood]

**** your stupid plane pearl.

[pearl]

im going to throw burning coal at you next time i see you.

[sherwood]

dude u missed it...mars standing at my car....and out of nowhere he gets hit in the head with a big ass rock haha...rich threw it from all the way over by mars car!!! hit mar right in the head hahaha

[dragonfly2k3]

holy OT batman. But while we're at it... Does anyone else hate the feeling of your teeth when you havent brushed since the night before. That like gritty feeling?

[NJGOAT]

The question defines Y=X so in scenario 2 X=0, Y=0, Z=0, no movement of anything, but it also defines X as a non-zero value. This is an invalid scenario. Unless the wording of the question is changed there is ONLY scenario 1.

But you are trying to define movement as velocity. Both the wheels and conveyor spin at a given RPM. I'm just going to give up, because I'm having a hard time trying to illustrate what I am talking about. The Scenario 2 thing was presented in a thread I read about this on another forum and it seemed to make sense to me. However, Scenario 1 is the "real world" scenario.

[thewake]

But you are trying to define movement as velocity. Both the wheels and conveyor spin at a given RPM. I'm just going to give up, because I'm having a hard time trying to illustrate what I am talking about. The Scenario 2 thing was presented in a thread I read about this on another forum and it seemed to make sense to me. However, Scenario 1 is the "real world" scenario.

That is because Scenario 2 makes no sense once you disect it (which it seems you have done). Let it go. Embrace scenario 1 as the only correct interpretation.

[Sincere]

I hate this one! But i just had to look. A plane is not propelled by its wheel so F a conveyor belt. All the wheel bearing stuff is crap. That's not part of the question. Maybe there's a 180mph breeze, then it will take off all by it self. No engines.

[wrx_snobordr]

1 week until we get a semi definitive answer. I am sure people will take issue to the methods used in testing the myth. I just saw a commercial and it looks like they are using a prop plane.

Get your official final answer in now, will it or wont it take off.

I say IT WILL!

[ITSTOCK]

1 week until we get a semi definitive answer. I am sure people will take issue to the methods used in testing the myth. I just saw a commercial and it looks like they are using a prop plane.

Get your official final answer in now, will it or wont it take off.

I say IT WILL!

It makes no difference whether the plane is prop or jet. It WILL take off.

[EvlEgl]

It will be on mythbusters Next week.

[wrx_snobordr]

It makes no difference whether the plane is prop or jet. It WILL take off.

I know this. I remember somebody saying something along the lines of if the prop produces enough thrust the plane could take off due to the large amount of air being pushed over the control surfaces. Of course this is false, but I was putting it out there in case someone wants to start disagreeing with their method before they even watch.

[marshallpre1]

Flight occurs because of the difference in pressure caused by MOVING air above and below the wings. If the plane just sits there, with its wheels spinning, it cannot take off. It's not the thrust that makes it fly, or the speed of the wheels. It's the difference in pressure. The reason you need a rear wing (downforce) on your car is the same thing. As you TRAVEL faster, the back end is starting to lift. The wing is used, in essence, as a upside down wing, pushing your car down. If your car sits on a belt, matching your speed, hence you're not going anywhere, you won't feel the lift... Therefore, a plane with ZERO NET VELOCITY should not take off

The post above^ can happen, but most likely not.

[ITSTOCK]

Flight occurs because of the difference in pressure caused by MOVING air above and below the wings. If the plane just sits there, with its wheels spinning, it cannot take off. It's not the thrust that makes it fly, or the speed of the wheels. It's the difference in pressure. The reason you need a rear wing (downforce) on your car is the same thing. As you TRAVEL faster, the back end is starting to lift. The wing is used, in essence, as a upside down wing, pushing your car down. If your car sits on a belt, matching your speed, hence you're not going anywhere, you won't feel the lift... Therefore, a plane with ZERO NET VELOCITY should not take off

My god, not this again.


CAR=DRIVELINE TO THE WHEELS, WHEELS MAKE CONTACT WITH GROUND, DIRECTLY INFLUENCING GROUND SPEED.

PLANE=DRIVELINE EITHER IN JET ENGINE OR PROP, CREATES THRUST AND MOVES THE PLANE, UNTIL AIR SPEED IS HIGH ENOUGH FOR THE WINGS TO SUPPORT LIFT.



If you see the difference, which I hope you do, you understand that being on a treadmill makes no difference, hence, AGAIN, the reason planes can take off on water (with opposite moving current), on ice and snow, and yes, on treadmills.

[marshallpre1]

^ I can see that. I guess it's just hard for me to picture how the thrust generates wind velocity over the plane's wings. If there is no wind, there is no flight. Maybe you are right. Many other posts online have shown this same statement.

EDIT: No you are right. Having the treadmill moving opposite direction only lessens the drag. In a perfect frictionless world, the wheels are doing nothing and in fact, just hold the plane up.

EDITx2: I can still see both sides. The one flaw I see with the "it's thrust no wheels" is thrust is forward motion. The forward motion generates the required windspeed over the wings by moving through the air. I guess the thrust argument argues (what a terrible statement) that IT IS moving through the air. Damn it, I guess I would just have to wait and see.

EDITx3: It will take off. I was thinking of it differently- thought of the treadmill like an invisible giant that holds the plane back- actually the wheels don't do squat and can't produce enough friction to hold the plane back.

[wrx_snobordr]

The post above, can happen, but most likely not.

For that to happen the prop would need to produce wind over the entire wing/tail surface area. You need a single prop from tip to tip greater than that of the planes width tip to tip, you essentially need a helicopter rotor.

The only possible way is to get a light plane, say a Piper cub, that has an incredibly low stall speed, place the plane in a headwind greater than the stall speed and simply pull back on the stick. If the wind stops blowing however, you are falling.


^ I can see that. I guess it's just hard for me to picture how the thrust generates wind velocity over the plane's wings. If there is no wind, there is no flight. Maybe you are right. Many other posts online have shown this same statement.


EDITx3: It will take off. I was thinking of it differently- thought of the treadmill like an invisible giant that holds the plane back- actually the wheels don't do squat and can't produce enough friction to hold the plane back.

HA, how quickly you came around to the correct side.

[NJGOAT]

It will take off.

[The Captain]

But will the plane move at all? I know the wheels are not propelling the plane, the prop/jets are doing that. But can the plane move on a conveyor belt? The reason the plane takes off is because of air movement over the wings. The jets are used to provide the thrust needed to get to the necessary airspeed. But if the conveyor belt provides the equal but opposite force, the plane will go nowhere.

edit: After more thinking, YES it WILL take off. The force of the conveyor belt is NOT equal and opposite, although at first thought it seems like it is. It is acting on the wheels which have no effect on the plane. The force of the jets are on the air, not the ground. The only difference the conveyor belt causes is for the wheels to move twice as fast, but the plane will still move as if the ground was stationary.

edit#2: Think of it like this. Take a rope and attach it to the plane. Put the plane on the conveyor. If you apply any force (pull on the rope) the plane will move forward due to that force. The thrust of the jets/props are just like the rope. Yes, the wheels will be effected, they will move much faster, but the plane will act as if the conveyor wasn't even there.

[dragonfly2k3]

I know this. I remember somebody saying something along the lines of if the prop produces enough thrust the plane could take off due to the large amount of air being pushed over the control surfaces. Of course this is false, but I was putting it out there in case someone wants to start disagreeing with their method before they even watch.

In gtheory, this could happen. The prop could produce enough movement of air over the AIRFOIL for the aircraft to lift off. The plane could also keep in flight without moving in the scenario of a true stall. Of course in the stall scenario the aircraft would need tremendous power, light weight, and a very low pitch prop. It could, however, happen.

[awdlaserbeam]

I hate this one! But i just had to look. A plane is not propelled by its wheel so F a conveyor belt. All the wheel bearing stuff is crap. That's not part of the question. Maybe there's a 180mph breeze, then it will take off all by it self. No engines.

atleast 1 person on this forum has a brain... this thread has been beaten to death... after it was beaten to no end 2 years ago...
In the 2 years everyone has been arguing about it, you could have gotten a dam plane, built a f'in conveyer belt and watched the plane sit on the ground for 2 years...
If you are running on a treadmill you are moving the same speed as the belt, and are not moving laterally relative to the earth... soo why would a plane be able to move relative to the earth? and if the plane isnt moving, then its not getting any wind under its wings to create and lift... Ever wonder why airplanes speed down a runway INTO the wind to take off... So unless a massive gust of wind comes along to lift the airplane off the ground, you can watch it spin its wheels forever

[jspek]

well this is gonna be on mythbusters next wed. so we will all find out and everyone can stfu about this lol

[awdlaserbeam]

haha i swear to god, as soon as i clicked submit reply.. i turned around and saw that commercial on TV..

[wrx_snobordr]

atleast 1 person on this forum has a brain... this thread has been beaten to death... after it was beaten to no end 2 years ago...
In the 2 years everyone has been arguing about it, you could have gotten a dam plane, built a f'in conveyer belt and watched the plane sit on the ground for 2 years...
If you are running on a treadmill you are moving the same speed as the belt, and are not moving laterally relative to the earth... soo why would a plane be able to move relative to the earth? and if the plane isnt moving, then its not getting any wind under its wings to create and lift... Ever wonder why airplanes speed down a runway INTO the wind to take off... So unless a massive gust of wind comes along to lift the airplane off the ground, you can watch it spin its wheels forever

Planes don't use their feet, wheels, for propulsion. For your example to be accurate, keep running but graba rope tied to a wall in front of you and pull, will you move forward relative to the earth, yes maam you will. The jet engines are the rope, they act on the air not the ground, they don't care what the wheels do, they will move the jet forward through the air. The whels will simply spin twice as fast but do not produce enough friction to counter the forward motion relative to the earth.

[pearl]

This myth airs on mythbusters this Wednesday.

[ITSTOCK]

Planes don't use their feet, wheels, for propulsion. For your example to be accurate, keep running but graba rope tied to a wall in front of you and pull, will you move forward relative to the earth, yes maam you will. The jet engines are the rope, they act on the air not the ground, they don't care what the wheels do, they will move the jet forward through the air. The whels will simply spin twice as fast but do not produce enough friction to counter the forward motion relative to the earth.

lol

"At least someone on this forum has a brain"
:rotfl:


And mythbusters don't need to prove it. It's already been proven.

http://www.youtube.com/watch?v=-EopVDgSPAk

[dragonfly2k3]

Lol, some of the people on here. It will take off. I dont understand how anyone could possibly have a different view on it. Either way, mythbusters will prove that it will infact fly. Its a shame that person in the youtube vid didnt have a larger, more ocntrolable plane that he could ahve actually flown.

[pearl]

mythbusters will probably mess it up

[WhiteXFire]

I'd like to pose a simple question to everyone, and it would be nice if several of the more outspoken people on this topic could chime in with their thoughts. I am not saying one thing over another, nor am I saying if it's even possible in the real world, I'm simply framing a slightly different problem.

A plane is sitting on one end (let's say the east end) of an "extra long" aircraft carrier that is as long as a regular runway. Both the airplane and the aircraft carrier are initially stationary, and there is no wind. At the same time, both the plane and the aircraft begin moving with the same rate of acceleration, but in opposite directions. That is to say, the plane begins accelerating west across the deck of the ship and the ship begins accelerating east across the water.

To an observer standing on the deck where the plane started, what does this look like? To an observer standing on the shore, what does this look like? When the plane reaches the end of the ship, will it take off or fall into the ocean?

[Vypurr]

^ In that case it would take off. The reason is that the plane is actually moving forward in relation to the ground that it is on. The direction that the carrier is moving makes no difference.

[WhiteXFire]

^ In that case it would take off. The reason is that the plane is actually moving forward in relation to the ground that it is on. The direction that the carrier is moving makes no difference.

Ok, so the person standing on the deck will watch it accelerate and take off like normal? Then what does the person on the shore see, it take off vertically without ever moving relative to his position?

[wrx_snobordr]

Ok, so the person standing on the deck will watch it accelerate and take off like normal? Then what does the person on the shore see, it take off vertically without ever moving relative to his position?

The runway, aircraft carrier, would need to be twice the length of the distance it needs to build speed and gain flight. If it normally takes 2000 feet for a jet to build sufficient airspeed to lift off, the carrier would need to be 4000 feet. The reason for this is because the wheel speed on the ship will be twice that of the jets airspeed, just as it would be in the conveyor example.

The person on the carrier would see the jet pull away at twice the speed of the person on the shore due to the fact that he is attached to the carrier that is moving in the opposite direction at an equal speed. To the person on the shore the jet would take off as normal. It would move away from them at its true air speed.

If they took a ruler and placed it in their field of view blocking the carrier but leaving the jet visible, the jet would accelerate along the ruler just as it would if you did the same thing to a jet taking off on land. The only difference would come from a minimal amount of friction from the imperfect bearings on the jets wheels.

[dragonfly2k3]

In this instance wrx is exactly correct on the aircrafts characteristics. It would run out of runway before take-off speed and would fall into the ocean unless it were twice as long. I would think that the person standing on deck would see it as normal as well but that im not sure of.

[WhiteXFire]

So then it's your belief that if the plane did not fire up its engines and only the aircraft carrier started moving, the plane would remain "stationary" to the observer on the shore and the movement of the aircraft would spin the wheels on the airplane, in essence rolling it across the deck until it fell off?

[ITSTOCK]

I'd like to pose a simple question to everyone, and it would be nice if several of the more outspoken people on this topic could chime in with their thoughts. I am not saying one thing over another, nor am I saying if it's even possible in the real world, I'm simply framing a slightly different problem.

A plane is sitting on one end (let's say the east end) of an "extra long" aircraft carrier that is as long as a regular runway. Both the airplane and the aircraft carrier are initially stationary, and there is no wind. At the same time, both the plane and the aircraft begin moving with the same rate of acceleration, but in opposite directions. That is to say, the plane begins accelerating west across the deck of the ship and the ship begins accelerating east across the water.

To an observer standing on the deck where the plane started, what does this look like? To an observer standing on the shore, what does this look like? When the plane reaches the end of the ship, will it take off or fall into the ocean?

You aren't understanding that the wheels attached to the runway are merely a "crutch" for the rest of the plane. They are there to limit friction, nothing more. If the runway is long enough, it's going to take off no matter what. You are looking in to this too much, or was that just a "what if" question?

[wrx_snobordr]

So then it's your belief that if the plane did not fire up its engines and only the aircraft carrier started moving, the plane would remain "stationary" to the observer on the shore and the movement of the aircraft would spin the wheels on the airplane, in essence rolling it across the deck until it fell off?

If the bearings were capable of frictionless motion and the plane was not chocked or tied down then yes, that is exactly what would happen. Sort of like pulling the table cloth off the table leaving everything else standing. However, since the bearings are not frictionless and the plane has a large amount of weight, the plane would most likely remain stationary or only roll a short distance when the air craft carrier accelerated.

An object in motion tends to stay in motion and an object at rest tends to remain at rest unless acted upon by another force. The force of the aircraft carrier moving may not be enough of a force to break the plane from its motionless state. The jet engines on the other hand, can easily break it free from that motionless state and once it is moving, the carriers motion either with it or against it, makes almost no difference. The plane is pushing on the air mass not the ground for propulsion.

[WhiteXFire]

You aren't understanding that the wheels attached to the runway are merely a "crutch" for the rest of the plane. They are there to limit friction, nothing more. If the runway is long enough, it's going to take off no matter what. You are looking in to this too much, or was that just a "what if" question?
Oh it's just a "what if", I'm only trying to stir the pot by framing it differently.

If the bearings were capable of frictionless motion and the plane was not chocked or tied down then yes, that is exactly what would happen. Sort of like pulling the table cloth off the table leaving everything else standing. However, since the bearings are not frictionless and the plane has a large amount of weight, the plane would most likely remain stationary or only roll a short distance when the air craft carrier accelerated.

An object in motion tends to stay in motion and an object at rest tends to remain at rest unless acted upon by another force. The force of the aircraft carrier moving may not be enough of a force to break the plane from its motionless state. The jet engines on the other hand, can easily break it free from that motionless state and once it is moving, the carriers motion either with it or against it, makes almost no difference. The plane is pushing on the air mass not the ground for propulsion.
Whistle, timeout! So we can actually agree that if only the carrier was doing the moving, then the plane would more or less remain stationary, perhaps jolted by the initial movement but nothing more? In other words, the plane would be unaware of the carrier's motion once started in this frame of reference? Kind of like me standing in the aisle of the airplane when it's going 600mph?

[ITSTOCK]

It's really no different than a plane flying in to a headwind.

[wrx_snobordr]

Whistle, timeout! So we can actually agree that if only the carrier was doing the moving, then the plane would more or less remain stationary, perhaps jolted by the initial movement but nothing more? In other words, the plane would be unaware of the carrier's motion once started in this frame of reference? Kind of like me standing in the aisle of the airplane when it's going 600mph?

Yes. This frame of reference also explains why the plane would take off. Even though the carrier is moving underneath it, the second the jet engines kick on the jet will roll down the runway and take off.

It's really no different than a plane flying in to a headwind.

Which is exactly how we take off and land, always into the wind if possible.

[dragonfly2k3]

I do believe that whitefire gets it! ha. Once the aircraft carrier was moving, the plane would not even know better, according to the plane it could either be A: moving east on the carrier or B: sitting still with a slow westward wind. It realy wouldnt know the difference.

[WhiteXFire]

Yes. This frame of reference also explains why the plane would take off. Even though the carrier is moving underneath it, the second the jet engines kick on the jet will roll down the runway and take off.

Ok, good. So, one last thing, I promise. Irregardless of the intent of the original problem, if this ship is going 100mph in relation to the water in one direction and the plane is going 100mph in relation to the deck of the ship in the other direction, is the plane's speed relative to the water 0mph? If you agree to that, would you agree that as long as the ship accelerated in relation to the water at the same rate that the plane accelerated in relation to the deck of the ship that the plane would remain at 0mph in relation to the water?

Which is exactly how we take off and land, always into the wind if possible.
And of course, but no more variables damnit!

[wrx_snobordr]

Ok, good. So, one last thing, I promise. Irregardless of the intent of the original problem, if this ship is going 100mph in relation to the water in one direction and the plane is going 100mph in relation to the deck of the ship in the other direction, is the plane's speed relative to the water 0mph? If you agree to that, would you agree that as long as the ship accelerated in relation to the water at the same rate that the plane accelerated in relation to the deck of the ship that the plane would remain at 0mph in relation to the water?


First, that is a damn powerful ship.

Second. If the ship was already moving at 100mph and the jet then turned on its engines it would essentially have a 100mph tail wind. This is of course figuring that their is no other wind motion, from any direction, what so ever, the only wind is generated by the ships motion and nothing else. The jet would need to overcome that tailwind, making its airspeed 0. This would I think take minimal power just to break the jets wheels free at which point the carrier would begin to accelerate underneath it as the plane sat still relative to the ocean. If the ship started to accelerate the jet would still remain stationary relative to the sea and the air with an airspeed reading of zero. Bring the jets up to full power and the jet would simply accelerate down the runway like normal. The airspeed would be say 60mph as would its ground speed and the airplane would become airborne . The speed on the ship would be 220, at the wheels. The initial 100mph, the 60 gained in one direction and the 60 gained in the opposite direction.

[WhiteXFire]

And like I said, I wasn't trying to relate it to the original problem or even have it be practical in the real world, just making sure people can agree on the laws of physics and relativity, lol. Anyway, carry on. Like I said in the original thread from 2 years ago, no one will ever agree on this, even after the episode, because there are multiple interpretations of an ambiguous original question. Even stating that, people will disagree because they just "see" the question as worded one way or another when they're reading the meaning that they understand.

[ITSTOCK]

Whoopty ****ing dooooooooooo


The plane flies, thanks for telling me something a 4 year old could do.

And I'm only bringing this one up to the top because there is another one there. This topic needs two threads to the numb nuts who couldn't get it through their thick heads that the plane would fly!

[naDintheHat]

Well mythbusters showed me.

[pearl]

thirty of you people got owned last night.

[TurboTagTeam]

thirty of you people got owned last night.

HaHaHaHaHahha

I was looking for this thread so I could post that. You-tube it bitches.....the planes flies.

[Renegade_]

I'm coming into this thread to say this:

The mother ****ing plane took off.

Bam.

[wrx_snobordr]

Settled. Many people need to go back to high school physics.

[foss]

Whoopty ****ing dooooooooooo


The plane flies, thanks for telling me something a 4 year old could do.

And I'm only bringing this one up to the top because there is another one there. This topic needs two threads to the numb nuts who couldn't get it through their thick heads that the plane would fly!

Aren't you just Mr. ****ing Modest...:screwy:

[pearl]

People who said it wouldn't fly:

///MpoweredM, 04 Turbo Spec, 07NHBPCivicSi, 90Laser, 97MaximaSE, awdlaserbeam, Chris_PA, Crzyguy972, DropTopChevy, Evo8kid, garrettej8, HatchSurfer3, james_ls, jc8889, Keeper1343, leg, martang, Metalhedd, mg23, OptiCon, Raven18940, redg2, rotarychainsaw, Roto, spoolinLSsol, ToyotaTat, turbo4g63, Vypurr, where'smyturbo?, whitezenki, Zarno

[dragonfly2k3]

Lol Pearl called em out!

[bastid]

He forgot me. I, too, said the plane wouldn't fly. Although, to my defense, it was my interpretation that the plane would remain motionless and under the assumption that the amount of speed on the treadmill would counteract any forward motion. After reading the responses and the question more thoroughly, I think I would have agreed that the plane would fly.

[OptiCon]

I'd heard this one 6 times before and a plane isn't effected by ground speed.

But apparently I voted incorrectly. :(