You have a plane and a conveyor belt.

[jagec]

Originally posted by: mchammer
jagec and SO, while you are correct that a very rapidly spinning tredmill could raise the RPM of the wheels to the point where they would have the "mass" to keep the plane still, in the OP it says that the treadmill would be limited to moving backward at the same speed the wheels (the plane) is moving forward. In that case, the wheels would spin at 2x what their normal RPM would be at any point throughtout the takeoff run. That would not be nearly enough to increase thier "mass" enough.

So basically, there is no way to argue under the terms of the OP that the plane would not take off, save wheel bearing with lots of friction.

Also :beer: to Tom for coming around.

I wasn't talking about relativistic effects. In my example, a Cessna burns through an entire TANK of fuel, and the conveyor ends up going ~2000km/h. I agree you'd need to change the control system from that stated in the OP, however.

Originally posted by: KK
But what the OP said is impossible because there is no way to match the conveyor to the wheels because the engine is going to push it physically forward. Therefore by physically moving forward falsifies the stipulation the the conveyor counteracts any foward wheel movement.

If the belt was able to keep the plane in one position then, no it wouldn't fly, but thats just asking too much from the belt.

There are two interpretations to the control system postulated in the OP. The first interpretation leads to an infinite conveyor speed for any nonzero plane speed. The second leads to a conveyor speed equal to the plane's ground speed ("ground" meaning the stationary area not on the conveyor), but in the opposite direction.

The belt CAN keep the plane in one position, but not with the control system in the OP.

 

[UlricT]

wheels will just spin twice as fast... DUH!

 

[glugglug]

It depends.
If the source of thrust is ABOVE the center of gravity, it won't take off, in fact the nose of the plane will dip until it hits the conveyor belt.
If the source of thrust is BELOW the center of gravity, the direction of torque will be such that the nose will tip up and the plane will take off.

 

[mchammer]

Originally posted by: glugglug
It depends.
If the source of thrust is ABOVE the center of gravity, it won't take off, in fact the nose of the plane will dip until it hits the conveyor belt.
If the source of thrust is BELOW the center of gravity, the direction of torque will be such that the nose will tip up and the plane will take off.

There's one we have't heard yet.

 

[mugs]

Originally posted by: mchammer

Originally posted by: glugglug
It depends.
If the source of thrust is ABOVE the center of gravity, it won't take off, in fact the nose of the plane will dip until it hits the conveyor belt.
If the source of thrust is BELOW the center of gravity, the direction of torque will be such that the nose will tip up and the plane will take off.

There's one we have't heard yet.

 

[SoylentG]

It will not take off. Jesus christ you people are ****** stupid if you think it will. The concept of airflight is based on lift, which is uneven air pressure above and below the aircraft. If there is NO AIR FLOW, there is NO FLIGHT.

If the conveyer belt instantaneously stopped, then it would take off. It would instantly reach a very high speed, which would allow it to gain lift.

Now, if the movement is being generated by something other than the wheels, then we can talk. But I've seen posts scattered that are claiming that the exclusive movement of the wheels will make the movement. If the thrust is from a propeller on the front of the plane, which facilitates air movement that is strong enough to create lift, I could see it happening. I'm a bit fuzzy on the subject, but lift is created when the air pressure above the plane is greater than below. So I'm reasonably sure this is logical.

 

[dug777]

Originally posted by: SoylentG
It will not take off. Jesus christ you people are ****** stupid if you think it will. The concept of airflight is based on lift, which is uneven air pressure above and below the aircraft. If there is NO AIR FLOW, there is NO FLIGHT.

If the conveyer belt instantaneously stopped, then it would take off. It would instantly reach a very high speed, which would allow it to gain lift.

Now, if the movement is being generated by something other than the wheels, then we can talk. But I've seen posts scattered that are claiming that the exclusive movement of the wheels will make the movement. If the thrust is from a propeller on the front of the plane, which facilitates air movement that is strong enough to create lift, I could see it happening. I'm a bit fuzzy on the subject, but lift is created when the air pressure above the plane is greater than below. So I'm reasonably sure this is logical.

indeed.

the only answers that allow it to take off break the rules in OP.

 

[Alaric360]

I think that you people who say that it will not take off are having a hard time thinking of an airplane as an airplane and not as a car. The wheels are not attached to the propulsion device(either the jet, or a propeller) ...The plane will still be moving down the runway because, as the wheels are free-rolling(and in this case frictionless) the plane is essentially not tethered to the ground. ...When the jet pulls in air, it will generate the thrust to move it down the runway at the same speed that it would have travelled with a 'concrete' runway. ...The only difference in this situation is that the wheels will be travelling much, much faster. (THE PLANE WILL NOT SIT STILL!!!!!! Thank God none of you are Aero Engineers)

 

[Alaric360]

OMG!!! I answered this without reading all of the posts on here. Some of your posts are (very, very.......very detailed, yet) COMPLETELY MORONIC!!!!! A plane is not a car. A car's wheels provide the drive that moves a car. I think you people are thinking that in this situation, the plane is sitting on a dyno. The plane will move forward with the same speed in this situation as if there were concrete below it. You would not need a more powerful engine, you would not need more runway, it would take off in exactly the same fashion. Anyone who cannot see this fact is probably in need of a G.E.D. because there is no way you passed high school physics class.

*Edit* ...Ok. now I have to eat a few of my words. It will not take off in EXACTLY the same way; The wheels will be spinning twice as fast as they would with concrete below them...I said that in the post above, but I know how some people won't consider 2 posts made 3 minutes apart to be from a continuous line of logic

 

[timosyy]

Why wasn't this thread murdered when it began. Isnt this like the biggest repost of all time?

 

[Alaric360]

...yes I know, but it's always nice to ream new retards who think it won't move hehehe

 

[jagec]

Originally posted by: SoylentG
If the conveyer belt instantaneously stopped, then it would take off. It would instantly reach a very high speed, which would allow it to gain lift.

:laugh:

Please refrain from opening your mouth in any physics discussions in the future.

 

[Alaric360]

...some genius actually decided to do calculations using some equation that wasn't posted to determine the torque provided by the conveyor belt but can't do a simple derivitive equation. The jet provides the acceleration(2nd derivitive of position), which moves the plane, speeding the wheels up(1st derivitive of position). Since the wheels speed up, the conveyor belt speeds up, but the jet is still providing acceleration(2nd derivitive of position), so the plane keeps moving(1st derivitive of position)......see the cycle? The plane moves because the method of propulsion is independent of the contact point with the ground. Plane takes off, simple as that. No more need for discussion, just a need to put it in ....s..m...a..l..l..e..r.......w..o..r..d..s......and a....l..i..t..t..l..e...s....l......o.....w......e........r

 

[JujuFish]

Originally posted by: timosyy
Why wasn't this thread murdered when it began. Isnt this like the biggest repost of all time?

It is essentially (as of this post) a 538 reply repost thread of a 399 reply thread.

 

[Alaric360]

Originally posted by: SoylentG
It will not take off. Jesus christ you people are ****** stupid if you think it will. The concept of airflight is based on lift, which is uneven air pressure above and below the aircraft. If there is NO AIR FLOW, there is NO FLIGHT.

If the conveyer belt instantaneously stopped, then it would take off. It would instantly reach a very high speed, which would allow it to gain lift.

Now, if the movement is being generated by something other than the wheels, then we can talk. But I've seen posts scattered that are claiming that the exclusive movement of the wheels will make the movement. If the thrust is from a propeller on the front of the plane, which facilitates air movement that is strong enough to create lift, I could see it happening. I'm a bit fuzzy on the subject, but lift is created when the air pressure above the plane is greater than below. So I'm reasonably sure this is logical.

Nope....completely illogical. *read the above posts* ...Before you call people

****** stupid

you better double check to make sure you don't belong on the short bus

 

[Alaric360]

Originally posted by: JujuFish

Originally posted by: timosyy
Why wasn't this thread murdered when it began. Isnt this like the biggest repost of all time?

It is essentially (as of this post) a 538 reply repost thread of a 399 reply thread.

I just love listening to people who think they know something about physics fail to calculate a first degree tensor

 

[Alaric360]

...btw, I'm not trying to say that the people who are just throwing their two cents in are stupid. ...If you're just throwing your two cents in, then you're probably just thinking about it for a second, thinking 'wait a minute' and then posting. ...The people that I am calling absolutely, unequivocally brainless are the people who are actually (at least seemingly) trying to provide mathematical proof that this plane will not move, which is an exercise in futility(trying to prove it that is)

 

[SlitheryDee]

LOL I jumped to the end of this thread and I can't believe so many people are still arguing about it.

here we have a wheel and a conveyor belt (bad ASCII art I know...)



<=<=<=<=<=<=<=|other mechanism|
O<---wheel
_>_>_>_>_>_>_>_>_>_>_>_>_ |treadmill|

If the wheel is being pushed forward by some mechanism that is independent of it's rotational speed then it will be propelled forward despite the opposite speed of the treadmill. If the wheel is not the driving force then how can the treadmill matching it's speed have a significant effect?

 

[SampSon]

Ok so I tried this out on one of my extra 737's and a bunch of old treadmills.
The damned thing didn't take off, it rolled into my neighbors house and started it on fire.

 

[Alaric360]

well I'm kinda just throwing all of this here now because I didn't know that we were talking about this again lol. This thread gets better every time someone new starts it up because there are always people who are so adamantly wrong about this that it makes me smile

 

[jagec]

Originally posted by: Alaric360
well I'm kinda just throwing all of this here now because I didn't know that we were talking about this again lol. This thread gets better every time someone new starts it up because there are always people who are so adamantly wrong about this that it makes me smile

It just makes me spend hours trying to correct them...next time this thread is near the top, I should just start a "You have a lobster and a magnet" parody, instead of opening it.

 

[Alaric360]

**...trying to get a 'lobster and a magnet' parody thread started by putting this thread at the top**

 

[lyssword]

"throw a toy airplane out of 400hp car on a dyno and see if it flies"
LOL yes the airplane will fly IF IT HAS 400 HP THRUST roflmao. you are so dumb... So your genious example relies on a toy airplane that has ZERO (0) thrust against the air and completely unrelated you stick a car into the argument. Many cars actually do take off the dyno but thats because of friction and inertia. Airplane WILL TAKE OFF ON A THREADMILL it will initially be a bit slower but it will take off for sure. Airplanes take off on rivers that go negative speed flow. asdl;fkjasd;flasdlklasdklasdlk I can't believe how dumb you guys are who claim to be "smart".
The only way airplane won't take off ona conveyer is if its tied down with cables to 1 place AND the cables are able to withstand the airplane's jet push. I've flown on passenger 747 boing airplane, and the wheels are there only to park and maneuver around. The plane goes 10 miles per hour (pulled by trucks/cars), then goes into straight line, accelerates to 300 mph in 10 seconds, end of story.
The wheels are nothing more than a rolling thingies that just coast along and keep airplane from damaging its belly while taking off/landing.

 

[TitanDiddly]

Do I need to get a video interview from a flight instructor with a doctorate in aeronautical science so I can put this thread to rest?

 

[lyssword]

Wind tunnel air sucked out at same speed = no take off. Treadmill where jet engines can create a pull/push from the air = take off.