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#617600 - 30/12/06 08:38 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Paul H Offline
Member

Registered: 23/08/01
Posts: 4757
Loc: Mt. Zion, IL
Quote:
Originally posted by JeffW:
OMFG!

Who cares about the bloody belt???

Chrike!!!

Refute the equations, if you can.

Otherwise you should endeavor to learn why the correct answer is correct.

Being indignant and obstinate will never make the incorrect answer correct.

One assumption I forgot to mention:

the airplane is capable of flying (with airspeed).

........

Quote:
Originally posted by TJ:
[b]Fine - just answer this:

Will the belt EVER turn?
Not unless the plane is MOVING (airspeed?)!![/b]
You are the biggest prick I know
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#617601 - 30/12/06 09:01 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Relavent information:

A plane is standing on a runway that can move (like a giant conveyor
belt). This conveyor has a control system that tracks the plane's
speed and tunes the speed of the conveyor to be exactly the same (but
in the opposite direction).

Will the plane be able to take off?

Let's agree on what assumptions are sensible then. All of the assumptions below apply to virtually all aircraft.

Plane is powered by engines that push air (props or jets)
Plane's speed is measured by a windspeed meter as well as GPS
Plane's wheels spin freely
Wheel friction is negligible when compared to thrust
Newtonian physics apply



Coefficient of dynamic friction:

Force of friction:

F(f) = -uN

(negative because it opposes motion)

u = coefficient of static friction

N = weight of plane

Notice velocity is not included!

That means that the velocity of the conveyor belt is irrelevant for all practical purposes.

F(t) is force of thrust

a = (F(t)+F(f))/m

You won't find a scenario where |F(f)| is greater than |F(t)|. Therefore, in ALL cases the plane moves with respect to the atmosphere, thus achieving lift.

Possible scenario:

t = 0 :

Plane 0 mph
Conveyor 0 mph
Wheels 0 mph

t = 15 :

Plane 60 mph
Conveyor 60 mph
Wheels spin @ 120 mph

t = 55:

Plane 160 mph
Conveyor 160 mph
Wheels spin @ 320 mph

....

The plane takes off.

Either learn why it is correct or refute it....

..scientifically.

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#617602 - 30/12/06 09:02 PM Re: Know that if you do not post in this thread today the human race may cease to exist
NY Madman Offline
Member
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Registered: 09/05/02
Posts: 5232
Loc: Florida
Quote:
Originally posted by JeffW:

Otherwise you should endeavor to learn why the correct answer is correct.
Whatever you say Jeff.

Just because you say the answer is correct it must be correct. [Freak]

Regardless of the fact that you have added absolutely nothing other than your claim that you are correct.

I'll try to keep that in mind.

Quote:
Being indignant and obstinate will never make the incorrect answer correct.
Considering we do not know the correct answer, who is being indignant and obstinate.

Quote:
One assumption I forgot to mention:

the airplane is capable of flying (with airspeed).
No shit.

That is once it has first obtained lift. There has been no evidence provided so far to support the assumption that this aircraft in the scenario will obtain the proper lift to achieve takeoff.

I'm still not committed to either argument. I just see flaws and lack of anything concrete here to support the claim that this aircraft will takeoff. That includes your posts.

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#617603 - 30/12/06 09:08 PM Re: Know that if you do not post in this thread today the human race may cease to exist
NY Madman Offline
Member
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Registered: 09/05/02
Posts: 5232
Loc: Florida
Quote:
Originally posted by JeffW:

Therefore, in ALL cases the plane moves with respect to the atmosphere, thus achieving lift.
You and others keep repeating the same exact FLAW.

The plane DOES NOT move in relation to either the atmosphere or the ground. It's engines are ONLY pushing air behind it.

You can't seem to get your arms around that fact. (You can stop posting Branden's drawing. How man times is that now?)

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#617604 - 30/12/06 09:45 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Quote:
Originally posted by Alpine Spirit:
I can see where it would take off and I can see where it would not there is just not enough information to say yes or no.

Simply because there were no limits put on the treadmill? And are the wheels totally magically not creating drag? And do the engines have enough power to overcome the weight of the plane dragging on the treadmill?

Hell if there were no limits put on the friction of the wheels on the ground and engines had insane power then yes I believe it could take off.

But this is a fictional situatoin so who is to say there are limits.

[Too much XOC] [Wave]
[drink]

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#617605 - 30/12/06 10:32 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Quote:
Originally posted by NY Madman:
Quote:
Originally posted by JeffW:

[b]Therefore, in ALL cases the plane moves with respect to the atmosphere, thus achieving lift.
You and others keep repeating the same exact FLAW.

The plane DOES NOT move in relation to either the atmosphere or the ground. It's engines are ONLY pushing air behind it.

You can't seem to get your arms around that fact. (You can stop posting Branden's drawing. How man times is that now?)[/b]
Holy shit. I'm gone most of the day and you CF'rs still can't grasp that the aircraft is not stationary and that the belt can't make it stationary.

You, Madman, are making an assumption when you state that the plane will not be travelling through the air. The conveyor is said to match the plane's speed, not keep the plane stationary. A plane's speed is measured either through the air or over the ground, not over the surface directly beneath it (if the last were the case, then an aircraft's groundspeed would change when it flew over running water or ocean currents).

Let's try it the other way. The aircraft is already airborne and on approach to the conveyor/runway for a touch-and-go. The runway is spinning at exactly the same speed in the opposite direction, just like when it took off. laugh Now, when the aircraft touches down (no brakes, remember, doing a touch-and-go) will it immediatly come to a complete stop and be unable to take off again (do the "go" part)?

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#617606 - 30/12/06 10:39 PM Re: Know that if you do not post in this thread today the human race may cease to exist
GrayHam Offline
Member

Registered: 17/04/01
Posts: 8849
a) I can't belive how I'm getting my ass whipped over on Full Tilt Poker right now.

b) I can't believe this fucking argument is still going on.

Damn.
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#617607 - 30/12/06 10:47 PM Re: Know that if you do not post in this thread today the human race may cease to exist
MidnightX Offline
Member
*****

Registered: 08/03/01
Posts: 3745
Loc: Jacksonville, Florida
Quote:
Originally posted by GrayHam:
a) I can't belive how I'm getting my ass whipped over on Full Tilt Poker right now.

b) I can't believe this fucking argument is still going on.

Damn.
a) Get a life.

b) Me either, man. Me either...

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#617608 - 30/12/06 11:07 PM Re: Know that if you do not post in this thread today the human race may cease to exist
XPLORx4 Offline
Member

Registered: 23/03/01
Posts: 1906
Loc: San Jose, CA
Quote:
Originally posted by NY Madman:
The wheels ARE NOT the single most important point. When are you going to face that fact? They are completely irrelevant to the discussion.
Do you really mean to say that the wheels are irrelevant? Because if that's true, then the next logical conclusion you should come to is that anything touching the wheels (such as the CONVEYOR BELT) is also irrelevant.
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#617609 - 30/12/06 11:11 PM Re: Know that if you do not post in this thread today the human race may cease to exist
NY Madman Offline
Member
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Registered: 09/05/02
Posts: 5232
Loc: Florida
Quote:
Originally posted by MattyX:

You, Madman, are making an assumption when you state that the plane will not be travelling through the air. The conveyor is said to match the plane's speed, not keep the plane stationary.
I'm not making any assumptions. You are failing to grasp the concept.

Let's go by your assumption for a minute. How far is this plane traveling through the air? Are you talking distance? Please tell me what distance and at what rate the plane is moving through the atmosphere? (We will assume for the question posed to you that the atmosphere is mostly static with no wind conditions).

If you are so sure of yourself, tell me the rate at which the air is flowing over the fuselage and wings if your plane is traveling through the atmosphere?

Also, the conveyor is not keeping the plane stationary. Once it's speed is matched with the plane, the plane is virtually stationary in relation to the surrounding atmosphere, the ground, and to an outside observer. It is not stationary on the conveyor.

Why is that such a difficult concept for you?

The concept of the plane's status in relation to the atmosphere and ground comes into play in aerodynamic principles.

I'll attempt to show that in my next post.

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#617610 - 30/12/06 11:15 PM Re: Know that if you do not post in this thread today the human race may cease to exist
NY Madman Offline
Member
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Registered: 09/05/02
Posts: 5232
Loc: Florida
Quote:
Originally posted by XPLORx4:

Do you really mean to say that the wheels are irrelevant?
As far as the aerodynamic forces involved with the plane in this scenario, yes, they are.

People are making calcualtions based on wheel rotation and such and that is flawed.

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#617611 - 30/12/06 11:20 PM Re: Know that if you do not post in this thread today the human race may cease to exist
NY Madman Offline
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Registered: 09/05/02
Posts: 5232
Loc: Florida
I have to rest up for New Years... so I will leave you with some things to ponder.

These are some facts regarding the plane in this scenario.

-- The plane becomes a static object in relation to the atmosphere once it's speed is matched with the conveyor.

-- The atmosphere, or air, is the fluid required for aerodynamics in this case which is airplane flight.

-- Since the plane became a static object in relation to the atmosphere, there is either none or little air flowing toward and over the wings and fuselage. This basically brings the difference in velocity between the solid object(plane) and the fluid(air) to almost ZERO.

-- The plane has ZERO groundspeed once it's speed has been matched by the conveyor.




As you can see above - NO FLUID, NO LIFT.

...Lift is a mechanical force. It is generated by the interaction and contact of a solid body with a fluid (liquid or gas)...

Since the plane in our scenario matched it's speed with the conveyor, some of the forces required for lift either no longer exist, or have been significantly reduced and/or compromised.

Since the plane is not speeding down an actual runway and pushing itself forward at a rapid rate of speed ...we have lost these forces and they can no longer be used to factor in lift for the aircraft in our scenario.

We have also lost DRAG, or at least a sizeable and signficant portion. We have lost enough to the point that we now basically only have two other forces involved, WEIGHT and THRUST.

Now would be a good time to explore Relative Velocity.



As you can see, we will also have a problem with our airplane's Relative Velocity.

...A fixed object in a static fluid does not generate aerodynamic forces. Hot air balloons "lift" because of buoyancy forces and some aircraft like the Harrier use thrust to "lift" the vehicle, but these are not examples of aerodynamic lift. To generate lift, an object must move through the air, or air must move past the object...

We know that there is little or no air moving past the body and wings of our aircraft in the scenario. We know that a key factor in generating lift is calculationg the Relative Velocity.

Let's take a closer look....



Is it looking good for our plane in the scenario?

Here are some examples...





As we already know, our hypothetical scenario is about as far from a wind tunnel type situation as you can get without being parked in a hangar.

Some things to consider once everyone comes to the realization that once the plane and the conveyor match speeds, our plane is virtually stationary in relation to the atmosphere.

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#617612 - 30/12/06 11:27 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Post whatever you like about the forces on an aero-plane, though I noticed that nowhere on your post did you illustrate any negative force on aircraft wheels or wheels being able to overcome a certain amount of friction.

Madman, answer my question now-
The aircraft is already airborne and on approach to the conveyor/runway for a touch-and-go. The runway is spinning at exactly the same speed in the opposite direction, just like when it took off. laugh Now, when the aircraft touches down (no brakes, remember, doing a touch-and-go) will it immediatly come to a complete stop and be unable to take off again (do the "go" part)?

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#617613 - 31/12/06 12:42 AM Re: Know that if you do not post in this thread today the human race may cease to exist
Claus Offline
Member

Registered: 05/07/02
Posts: 4373
Shut the fuck up Donniem you are out of your element,,,,
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#617614 - 31/12/06 02:40 AM Re: Know that if you do not post in this thread today the human race may cease to exist
Xterrian Offline
Member
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Registered: 08/12/00
Posts: 2014
Loc: Fort Lewis, WA
I really can't believe this argument is still going on. I went shooting with some friends, went to the casino and won $400 playing black jack and celebrated my wife's birthday since this was at 18 pages.

I worked on aircraft for 1 1/2 years and can tell you with absolute certainty that the plane in this scenario would develop forward movement in relation to the air even if the conveyor belt moved at an infinite speed. The drag caused by the wheels could never overcome the forward thrust of the engines if they were capable of turning. The only way to keep the plane from taking off would be to attach it to something static or the conveyor belt itself if the wheels are not locked. Oddly enough, a car would stay in one spot in this same scenario, but then the car doesn't have an external motive force like a prop. You must think of it in these terms, the plane doesn't pull itself along the runway, it pulls itself through the air, and it just appears to move along the runway. If the plane wouldn't move then a lot of bush pilots would have a hell of a hard time taking off upstream off of rivers, but they usually do it that way unless there is a severe tailwind.(Easier to steer with the rudders on the floats upstream.)

Now if the bush pilot throttles back so that the reistance to the floats was the same as the forward thrust of the engine they would stand still in relation to the river, but even if the river(conveyor belt)were moving at an infinite speed it couldn't cause enough resistance to stop the plane from moving forward once the floats were on plane.

Madman's argument would be valid if the plane never moved in relation to the air around it, but the plane would move in relation to the air no matter how fast the conveyor belt runs. The wheels would just spin up to match the conveyor belt speed until the plane left the ground while moving forward in relation to the air around it.

If you still think the plane won't take off, PM me and I'll give you my phone number and we can discuss it. Please don't post any more arguments against it here. I think you're smarter than this one thread is making you look. Rinky can post anything he wants, I don't agree with anything he ever posts anyway. wink
_________________________
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#617615 - 31/12/06 02:55 AM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


The wheels spin as a result of friction with the ground and are independent of the thrust being provided by the engines. A conveyor can't stop the forward motion of the plane.

The hypothetical is flawed. The conveyor can't stop a planes forward motion. Speeding it up only slows it down by the amount of friction that is being created between the wheels, bearings and ground.

The only way it works would be to in some way increase friction to counter thrust. Only then would forward motion be stopped.

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#617616 - 31/12/06 03:11 AM Re: Know that if you do not post in this thread today the human race may cease to exist
BlueSky Offline
Member

Registered: 17/08/00
Posts: 2286
Loc: Georgia
The key is forward motion, which has everything to do with the tires because that's how the airplane - REGARDLESS OF HOW PROPELLED - moves across the ground.

Let go of how the tires are being propelled (moved forward) and think of it this way: a tire rolling over a fixed surface results in forward motion. A non-VTOL (Vertical Take-Off/Landing) fixed-wing aircraft MUST have forward motion to achieve flight from a standing start.

On a runway, imagine the plane is sitting at point A on a straight line, with points B through Z representing the takeoff roll, Z being rotation (when the nose is lifted for takeoff).

Power is applied and that power - engine thrust - is converted into forward motion that takes the plane through points B to Z because again, a tire on the ground, regardless of HOW it is moved forward, covers a given distance for each revolution (i.e. forward motion). So if NYMadman's observer was standing alongside point A, the plane would leave him/her behind as it accelerated.

Distance traveled equals 2πR, where R is the wheel's radius. Let's just say the answer to that equation in our scenario is 12 feet. But the treadmill moves 12 feet in the opposite direction. The tires are attached to the plane, we can all agree on that, right? So if:

2πR = 12 feet but treadmill motion = -12 feet then the resulting forward motion is ZERO.

For the plane to move forward, 2πR MUST be greater than the distance the treadmill moves backward, but the scenario says the belt matches the plane's speed, so the result can't be greater than zero.

On a runway of course, there's no counter-motion backwards so 2πR is always greater than zero, resulting in forward motion.

In the scenario presented, points B through Z are on the treadmill, so as engine thrust is applied, it is NOT converted into forward motion because the treadmill accelerates as the thrust does. Points A-Z simply pass under the plane, and it remains relatively stationary beside the observer, NOT leaving him/her behind.

No relative wind (airflow over the wings), no lift, no takeoff.

For the "what if it was on perfect ice" argument, that doesn't fly (ha!) because even though the tires might not rotate, there is still forward motion when thrust is applied because the tires' purpose (reducing friction to allow relatively easy forward motion) has been eliminated by the ice's absence of friction. The plane would still cover points A to Z on the takeoff roll.

BTW, asked my wife so as to get an independent opinion, and hers was profound: "Don't know, don't care. You guys need to get a life." Yes, dear. laugh

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#617617 - 31/12/06 03:40 AM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


The thrust provided by the engines is independent of the wheels. It doesn't even have to be wheels most of you guys are caught up on that. What if the plane was floating on a pocket of air like an airboat. What does thrust care what the ground is doing? The ground/conveyor could be traveling at a 100 MPH and it would not affect the floating plane right? OK so lets start the engines and create some thrust. What happens to the plane then? It moves forward at a gradually increasing speeed, generates lift and takes off.

If you think about it the planet is a big ass conveyor traveling/spinning at thousands of miles per hour. According to you guys we would never be able to take off.

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#617618 - 31/12/06 03:50 AM Re: Know that if you do not post in this thread today the human race may cease to exist
BlueSky Offline
Member

Registered: 17/08/00
Posts: 2286
Loc: Georgia
Quote:
Originally posted by Timmah:
The thrust provided by the engines is independent of the wheels. It doesn't even have to be wheels most of you guys are caught up on that. What if the plane was floating on a pocket of air like an airboat. What does thrust care what the ground is doing? The ground/conveyor could be traveling at a 100 MPH and it would not affect the floating plane right? OK so lets start the engines and create some thrust. What happens to the plane then? It moves forward at a gradually increasing speeed, generates lift and takes off.

If you think about it the planet is a big ass conveyor traveling/spinning at thousands of miles per hour. According to you guys we would never be able to take off.
I just added something to my post above so you missed it. It DOES matter what the tires do because they're attached to the plane. Here's my addition:

Distance traveled equals 2πR, where R is the wheel's radius. Let's just say the answer to that equation in our scenario is 12 feet. But the treadmill moves 12 feet in the opposite direction. The tires are attached to the plane, we can all agree on that, right? So if:

2πR = 12 feet but treadmill motion = -12 feet then the resulting forward motion is ZERO.

For the plane to move forward, 2πR MUST be greater than the distance the treadmill moves backward, but the scenario says the belt matches the plane's speed, so the result can't be greater than zero.

On a runway of course, there's no counter-motion backwards so 2πR is always greater than zero, resulting in forward motion.

------------------------

And you didn't do what I asked - FORGET the method of propulsion because it DOESN'T MATTER.

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#617619 - 31/12/06 05:18 AM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


The tires are just rolling. They are just there. Heck, they don't have to turn at all given enough wind to have the plane take flight. It doesn't matter what they are doing.

Until the friction being created by them rolling overcomes the thrust provided by the jet engines the plane will be able to get enough speed to take off.

You're caught up on the wheels and for some reason you keep thinking they are propelling the plane.

Lets say your on rollerskates standing on a moving sidewalk. For arguements sake lets say your stationary to the rest of us and the walkway is moving underneath you without you having to do anything to brace yourself to stay in place.

I walk up behind you and push you forward. Do you move? Lets say I pass you a tow rope and walk along side the moving walkway and pull you against the traving sidewalk direction. Do you move in the direction I pull or do you stay still?
Would you still move if in my direction if the sidewalk was going 2x faster than I was walking?

Just think of the jet engines as a tow rope.

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#617620 - 31/12/06 05:24 AM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


You folks are silly.

The plane will not move (or it will if you add the element of time).

Break it down and simplify it, we just need to know if an object on the treadmill would move forward. If it can, then with wings, it can fly.
Let's remove the wings from the plane and the type of thrust from the plane, hell, do it in a vacuum. Now we have an object on a treadmill, it can be a box with 4 wheels, maybe a Hummer.

Apply a force to that box with 4 wheels, maybe with your hand, or maybe with a jet engine like in the scenario. If the treadmill matches the rotation of the wheels exactly, our object, box with no wings, Hummer, whatever, will remain in the same spot.

By matching the speed of the wheel rotation exactly, you have basically created 100% resistance, just like a wall. Park a plane against a wall, and see how far it gets.

Let's turn off the engine. Now, spin that treadmill up to 150 mph, roughly takeoff speed. The wheels on the plane are turning at 150mph as well. The plane is stationary.

Walk up a down escalator and match it's speed. Imagine that the escalator would speed up if you started running, keeping you in the same spot. Imagine a friend giving you a push from behind, making you run faster, but at the exact moment, the escalator speeds up again. Still can't get upstairs to Starbucks.

The only way it could actually move forward is from latency of the treadmill system adjusting to each increment in rotational speed and falling just a tiny bit behind. That was not part of the equation though.

PS: More pictures of Evangeline Lily please.

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#617621 - 31/12/06 05:27 AM Re: Know that if you do not post in this thread today the human race may cease to exist
Southernx7 Offline
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Registered: 24/03/03
Posts: 1251
Loc: Sunny Florida
The Jags still suck, the Jags still suck.....everybody....

Sorry to interupt this debate....but Kansas is going to whip our asses today, you know how I knkow this? It's easy.......The Jags still suck, the Jags still suck...
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#617622 - 31/12/06 05:57 AM Re: Know that if you do not post in this thread today the human race may cease to exist
Mobycat Offline
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Registered: 12/09/00
Posts: 8374
Loc: the hue of dungeons and the sc...
Quote:
Originally posted by Mobycat:
Quote:
Originally posted by XPLORx4:
[b]
Quote:
Originally posted by Mobycat:
[b]So someone answer this ignored comment:

If the engines are off, and if there was NO friction, and that conveyor belt moved, the plane shouldn't budge - it will just have rolling wheels.
That's a correct statement if you mean there's no friction in the wheel bearings. (You need friction between the tires and conveyor, otherwise the tires wouldn't start rolling).[/b]
Yes, in the wheel bearings.

So, if there is friction, the plane will roll backwards?

Can the plane match the force with its engines?

What if it can't do anything *beyond* matching it?[/b]
Why is it that this scenario seems to be possible UNTIL you get to the last question?

What magic appears to make the plane suddenly overcome the friction? When it can ONLY match it? (Which is what the conveyor belt is doing?)
_________________________
"Nature has constituted utility to man the standard and test of virtue. Men living in different countries, under different circumstances, different habits and regimens, may have different utilities; the same act, therefore, may be useful and consequently virtuous in one country which is injurious and vicious in another differently circumstanced" - Thomas Jefferson, moral relativist

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#617623 - 31/12/06 06:35 AM Re: Know that if you do not post in this thread today the human race may cease to exist
BlueSky Offline
Member

Registered: 17/08/00
Posts: 2286
Loc: Georgia
Quote:
Originally posted by Timmah:
The tires are just rolling. They are just there. Heck, they don't have to turn at all given enough wind to have the plane take flight. It doesn't matter what they are doing.
Yes, I'm afraid it does matter because they're attached to the plane and represent the means by which the plane moves forward, whether it's being towed by a tractor or propelled by its engines.

Quote:
Originally posted by Timmah:
You're caught up on the wheels and for some reason you keep thinking they are propelling the plane.
I spent 20 years in the airline industry and have a very thorough knowledge of aircraft and the theory of flight. I assure you that I DO know that aircraft wheels are not powered, and spin freely except for being slowed by brakes.

Quote:
Originally posted by Timmah:
Lets say your on rollerskates standing on a moving sidewalk. For arguements sake lets say your stationary to the rest of us and the walkway is moving underneath you without you having to do anything to brace yourself to stay in place.

I walk up behind you and push you forward. Do you move? Lets say I pass you a tow rope and walk along side the moving walkway and pull you against the traving sidewalk direction. Do you move in the direction I pull or do you stay still?
I stay still, IF the treadmill matches my speed, which it does in this scenario.

Believe it or not, you're the one who doesn't get it. :rolleyes:

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#617624 - 31/12/06 07:07 AM Re: Know that if you do not post in this thread today the human race may cease to exist
Rockaholic Offline
Member

Registered: 18/02/02
Posts: 1632
Loc: Reading, MA
Ok, I screwed up in my last posts with respect to the 3rd party - so ignore those - I ended up confusing myself when people began mention 3rd party observers to the scenario - and made a mistake. If the plane is not moving in relation to the 3rd party observer Like in my aircraft scenario) then the plane does not fly. However my aircraft scenario is flawed because there is nothing to prevent the airplane from moving with respect to the gound. Thus the plane to a 3rd party observer could not appear to stay in one spot.

The assumption that the airplane on a conveyor remains staionary with respect to the ground is wrong.

Think about this - carefully.

The conveyor is set up to match the airplanes speed, so if the airplane is moving at 10 mph, so is the conveyor in the exact opposite direction.

The originally scenario does not say that the planes causes the conveyor to move, but that the conveyor is moved by some other control to match speed of the plane.

So if the plane is off of the conveyor on hard ground moving towards the conveyor at 10mph, then the conveyor is still going to move at 10mph in the opposite direction...

Now replace the Airplane with a car (make it a Front wheel driven car) and with the same setup as above, but this time the car drives onto the conveyor.
Once the front wheels of this car touch the conveyor the car stops it's forward motion with respect to the ground - with the front wheels on the conveyor spinning at 10 mph on the conveyor and the rear wheels (which were only spinning because the front wheels were moving along the ground and the rear wheels have to follow) are on the ground stationary.

Now replace the Airplane with another car (make it a 2wd Xterra) and with the same setup as above, what happens when the Xterra drives onto the conveyor? When the front wheels contact the conveyor they (being free spinng) double their speed as they contiune to move up the conveyor until the rear wheels get onto the conveyor. At that point, all 4 sets of wheels are spinning at 10 mph and the Xterra stays in one spot with respect to the ground.

Now, an Airplane has front wheels and rear wheels, so what happens when the airplane moves onto the conveyor?
Does the plane stop it's forward motion when the front wheels touch the conveyor belt? No, the front wheels, which are free spinning, begin to move at 2x the belts speed and the plane continues to move with respect to the ground...
Does the plane stop when all of the wheel are on the conveyor? No, all of the wheels are free spinning so all of the wheels double their speed, the plane continues to move with respect to the ground.
_________________________
Jeffrey
I'm just trying to put my tires on the rocks of life.

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