Will it take off?

[flannj]

Depends. Is God allowed to break the laws of physics? If a person can lift 200# and also weights 200#, yet a person cannot put their hands under their own feet and lift themself. Can God?

Does God have feet?

Yes.

Genesis 1:27

So God created man in his own image, in the image of God created he him; male and female created he them.

Here we go again! []

No, He doesn't.

http://www.venganza.org/

[Champagne taste beer budget]

Oh man! You said "fly." You really mean "pass" right?

LOL... you certainly don't think they could DRIVE through the earth, do you? [au]

[ZAKO]

Not mutch of an appendenge.

[mas]

Oh man! You said "fly." You really mean "pass" right?

LOL... you certainly don't think they could DRIVE through the earth, do you? [au]

Buckaroo Banzai did...

[mas]

Oh man! You said "fly." You really mean "pass" right?

LOL... you certainly don't think they could DRIVE through the earth, do you? [au]

Buckaroo Banzai did...

[ZAKO]

Garrison.......You had to look it up.....Mine is from memory.

[Ray Garrison]

Garrison.......You had to look it up.....Mine is from memory.

uh, okay... I looked it up.

I'm reasonably familiar with the Constitution of the United States, too. If I was going to quote a passage from it to post on this forum, I'd look it up... I always prefer to refer to an authority when I'm trying to make a point. Tends to keep me from unnecessarily inserting my foot in my mouth. Usually.

[maxg]

Phew - the whole thread just read.

Late to the thread and slow on the uptake - it wasnt till page 23 that I got why the plane will take off.

It doesnt matter what the wheels are doing - it doesnt matter whether there is a moving runway or a stationary one - or even which direction it is going in.

Boy I can be dumb sometimes.

Good question though....

[D-MAN]

Airflow over the wings is what makes it fly, and with zero air speed over the wings, zero flight.

DM

Why do you assume there is "zero air speed"? What force is exerted by the conveyor on the plane to impede the plane's forward motion?

I have to go out for a while. So you have time to think.

Are you NUTS?! the jet engines exhausting one way and the conveyor going the opposite direction at exactly the same compensating speed? Try ZERO air speed...

To think otherwise is shockingly stupid, but I see you've already signed up for that one.

I'm going out for awhile so you have time to not be as ...

DM

DM,

As the biggest former proponent of "won't fly" I understand where you are coming from. but it will develop ground speed, thus having air moving over its wings. Think of it is ice, if you were in a car if you pressed the accelerator the wheels would just spin and spin, but with a plane you easly move forward. A plane, assuming tires with zero or no friction would just sit on the belt/moving runway in fixed position even if the belt is moving 100 mph in reverse. It is sort of a trick question, the wording makes you assume that the plane would remain stationairy because the belt is moving in reverse. However, with an airplane, brakes off, they are free spinning so the belt can move in reverse at 5 mph or 500 mph, they are just going to make the wheels spin, the plane can still go forward because the prop/jet will move the plane ahead independant of the wheels spinning in reverse. The wheels are free spining. As soon as you apply power to the airplanes engine it would roll forward because there is nothing to hold the airplane back. The way I originally read the question I thought that the plane would remain in one place, and I agree with you, it would not fly if it did so. But it won't remain in one place, it will move forward, it will gather ground speed, it will have air moving air over its wings, it will get up to stall speed, it will rotate, and it will take off, over just as long a distance as if it was sitting on concrete.

Travis

Travis, that's still incorrect. The free wheeling wheels corresponding to the backwards motion of the conveyor belt would mean that the plane itself remains stationary relative to the ground position, as long as the conveyor belt is exactly compensatory with the speed (force) of the engines.

Stationary at the wings means no air flow over them, and hence, no flight, regardless how much the engines push, no forward motion is achieved. The whole thing relies on the conveyor belt exactly cancelling forward motion.

Now, if the compensatory nature of the conveyor belt is "up in the air", then possibly, so could the plane be... but if I read the original premise correctly, flight would be impossible.

DM

[D-MAN]

Airflow over the wings is what makes it fly, and with zero air speed over the wings, zero flight.

DM

Why do you assume there is "zero air speed"? What force is exerted by the conveyor on the plane to impede the plane's forward motion?

I have to go out for a while. So you have time to think.

Are you NUTS?! the jet engines exhausting one way and the conveyor going the opposite direction at exactly the same compensating speed? Try ZERO air speed...

To think otherwise is shockingly stupid, but I see you've already signed up for that one.

I'm going out for awhile so you have time to not be as ...

DM

DM,

As the biggest former proponent of "won't fly" I understand where you are coming from. but it will develop ground speed, thus having air moving over its wings. Think of it is ice, if you were in a car if you pressed the accelerator the wheels would just spin and spin, but with a plane you easly move forward. A plane, assuming tires with zero or no friction would just sit on the belt/moving runway in fixed position even if the belt is moving 100 mph in reverse. It is sort of a trick question, the wording makes you assume that the plane would remain stationairy because the belt is moving in reverse. However, with an airplane, brakes off, they are free spinning so the belt can move in reverse at 5 mph or 500 mph, they are just going to make the wheels spin, the plane can still go forward because the prop/jet will move the plane ahead independant of the wheels spinning in reverse. The wheels are free spining. As soon as you apply power to the airplanes engine it would roll forward because there is nothing to hold the airplane back. The way I originally read the question I thought that the plane would remain in one place, and I agree with you, it would not fly if it did so. But it won't remain in one place, it will move forward, it will gather ground speed, it will have air moving air over its wings, it will get up to stall speed, it will rotate, and it will take off, over just as long a distance as if it was sitting on concrete.

Travis

Travis, that's still incorrect. The free wheeling wheels corresponding to the backwards motion of the conveyor belt would mean that the plane itself remains stationary relative to the ground position, as long as the conveyor belt is exactly compensatory with the speed (force) of the engines.

Stationary at the wings means no air flow over them, and hence, no flight, regardless how much the engines push, no forward motion is achieved. The whole thing relies on the conveyor belt exactly cancelling forward motion.

Now, if the compensatory nature of the conveyor belt is "up in the air", then possibly, so could the plane be... but if I read the original premise correctly, flight would be impossible.

DM

[Cal Blacksmith]

I can't imagine that this thread has gone on so long. The
answer is



yes the aircraft will take off and fly in this
example provided the "moving runway" is of a normal length of a
runway.



The thing many people can't get over is they are stuck on how a CAR derives
forward thrust. A CAR would remain stationary but an aircraft WILL NOT. Thus, because it will not remain stationarry, it will generate airflow over the wings and when the airflow is enough, it will TAKE OFF!

Aircraft DO NOT get any of their forward motion from the wheels, none, zero,
zip, nada! The force from the engine is used to push against AIR, NOT THE
GROUND!! In the example given, the aircraft will accelerate as normal and take
off and fly, again providing that the runway is long enough to allow a normal
take off!! The motion of the ground is of no importance!



For example, I once flew an aircraft BACKWARDS over the
ground. Yes that is right, the ground was going backwards relative to the
position of the aircraft. This is possible because I was flying into a HEADWIND
that was moving faster than my forward speed. The aircraft acted normally as it
was indeed moving 80 mph through the air but the air I was flying into was
moving the opposite way at 100mph, thus my position OVER THE GROUD was moving
backwards to the direction the aircraft was flying.

[maxg]

"The free wheeling wheels corresponding to the backwards motion of the conveyor belt would mean that the plane itself remains stationary relative to the ground position, as long as the conveyor belt is exactly compensatory with the speed (force) of the engines."

D-man,

I am massively sympathetic to this interpretation as I was there but 10 hours ago. The error is that, in fact the conveyor belt is not capable of holding the plane stationary - whatever it is doing. It is capable, solely, of making the wheels spin. The motion of the plane is determined by the engines which are acting on the frame itself.

Whatever the conveyor belt attempts to do in counterbalancing the force of the engines the plane will move off pretty much as normal and probably take a similar distance to get off the ground. the wheels will be turning at the sum of the take off speed and the conveyor speed - which could be a million miles and hour and still not make any difference.

Get it?

[Travis In Austin]

DM,

Let me take one more crack, the conveyer will not cancel out the air speed. If the ice example did not do the trick try this. Imagine a car on the conveyer belt, since the power comes from the wheels, the faster and faster the wheels spin, the faster and faster the belt moves in reverse and the car remains fixed in place.

Now picture the air plane on the conveyer belt, with a rope tied to the front of it. Now lets say they turn the belt on to run in reverse, it does not matter what the speed is, 50 mph, 70, 100, 500, it does not matter because that rope is tied to a big fixed object. The plane will stay fixed in place, because it is being held in place by the rope, but acually it says in place because the wheels are free spinning, but lets just say there is enought friction in the wheels to need the rope to hold it in place. Now lets add a little thrust, lets pull on the rope with a big truck, we will be able to easy pull it down the run way, because there is noting to hold the plane back. The wheels are free spinning. You could run the belt/runeay in reverse at 100 mph or 500 mph, if you want to pull it 30 mph it will easy do it, the wheels just spin 30 mph faster, 130 or 530. The pulling on the rope is the same thing the propeller is doing, it is pulling the airplane through the air.

The other thing is picture is a bike on a moving sidewalk with the same functions, the faster you ride the faster the sidewalk moves in reverse. If you were on the sidewalk and on the bike you would never go anywhere. The faster you rode the faster the sidewalk moves backwards. Now step off the bike, step of the sidewalk onto the street, but still hold up the bike by the handlebars on the sidewalk. So you are off the sidewalk but reaching over to the bike which is sitll on the side walk. Tell them to start the sidewalk in reverse and you hold the bike in place with almost no effort. That is because the wheels are freespinning backwards. You decide to walk up the street and you start pushing the bike by the handlebars. You could actually do this on a treadmill for real. You would be able to push the bike up the sidewalk easily while walking on the street, the wheels just spin a little faster in reverse then they were before. You could even start to run with the bike on the sidewalk as long as you stayed on the street.. That is because you are able to apply force, thrust, independant of the sidewalk because you are on the street. This is what a jet engine does, it pushs the plane through the air. It does so independant of the sidewalk. The conveyer pushing against the planes wheels is not enough to hold it back when power is applied, it does not matter if the belt is spinning 50 mph in reverse, or 500 mph because the are free spinning. Just like it does not matter if you are pulling the plane with a rope, or pushing a bike by the handle bars.

The plane is able to get up to it's take off speed, by either being pulled (propeller) or pushed (jet).

Travis

[Cal Blacksmith]

I saw this on another forum I frequent and found some of the commentary interesting. I don't know the answer although I've got an opinion. It WAS interesting seeing the answers/thoughts some people gave (2 pages worth).

I'm copying it exactly like he had it there

a plane is standing on a movable runway( something like a conveyor).as the plane moves the conveyor moves but in the opposite direction.the conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

the question is

will the plane take off or not?

(ps its been debated to death on other forums, its always fun to see how people present the theory behind there answer)

Perhaps it will help to look at the question again. The question states in part, "as the plane moves" this indicates that the aircraft WILL MOVE. if it did NOT move, the conveyor belt will remain stationarry, the problem specifically states that the aircraft does move.

If the plane does move, it WILL generate lift. If it generates lift, it will fly!

Aircraft thrust against AIR, nothing else, thus whatever speed the conveyor belt moves is of no importance to the aircraft as it is disconnected from the ground for any and all propulsion reasons.

Just as a boat does not use the bottom of the lake, stream etc for propulsion, an aircraft does not rely on the ground either. In fact, an aircraft needs to be handled and taxied on the ground just as if it was flying. An aircraft is to be concidered AS flying until the wings are tied down, the wheels are chalked and the engine is off. This is because it operates in a different relm than that of vehicles that operate ONLY on the ground, that relm is the air and nothing else.

[dtel's wife]

Geez guys, twenty five pages and still going at it?[]

[klipschaholik]

Yep, one convert at a time. []

[Rockets]

RE:

Geez guys, twenty five pages and still going at it?

[Speedball]

No doubt, it will take off. If it is allowed to fly freely (not anchored down) it will just fly away leaving the conveyer to go how ever fast it want's to.

And this is my first reply......

[BEC]

!!!

[PhilMays]

That's too funny Bob!

Can you put anything you want in the space?