Plane on conveyor... Will it ever take off?

Guest.anon

3rd April 2006 - 08:51 PM

QUOTE (Guest.anon+Apr 3 2006, 08:48 PM)

He should also note that a boat moving through the water is not the same as a plane moving across a runway. Plane wheels do not move THROUGH the ground. They move on top of it thus the ground provides almost no resistance except through that provided by an incline.

A boat moving through the water has to divide the water, and in the case of a river, overcome the force of the current pressing up against the hull.

Also Atl5p has no concept of what actually makes a turbine engine, jet engine, or propeller actually propel a plane.

Contrary to popular belief, Atl5p, a prop plane doesn't fly by the propeller forcing air over the wings... the propeller spinning through the air presses up against the air which results in a force on the frame which pulls the plane through the air.

This is one of the many reasons every thing you say is ***-hattery.

Let me clarify... the propeller is shaped like a wing and by moving through the air, the propellers generate horizontal "lift" which we call thrust, while the planes actual wings generate vertical lift.

Think of helicopters. The rotors are wing shaped and generate lift.

Atl5p

4th April 2006 - 12:31 AM

QUOTE (Fynlcut+Apr 3 2006, 12:14 PM)

Go get a traction kite, a set of rolerblades, and take your treadmill outside. When the wind is blowing 8 mph, strap on your rollerblades, start up the treadmill, and launch the kite. Now get on the treadmill, you will understand why a sailboat CAN move upstream. You will understand why the source of power is important. You will understand.........ahh who am I kidding no you won't

I don't disagree that a sailboat CAN move up a river...

But a 10knt sailboat CANNOT move up a 10knt river...period.

Neither can a 10knt boat...

I've BEEN there and DONE that...in case you missed...Straight of Florida...Gulf Stream...(?)...ring a bell? I've gone over this before...9knt sailboat vs 6knt current = 3knt groundspeed...done it done it done it....

Now, put a model plane on a treadbelt...move the plane over the belt's surface...turn up the treadbelt at the same speed...match the plane's beltspeed with the treadbelt's belt in the opposite direction...Plane sees 0 IAS...been there, done that....done it done it done it...

atl5p

Atl5p

4th April 2006 - 01:06 AM

QUOTE (mr_homm+Apr 2 2006, 02:10 AM)

Is it the wheelspeed? Under this interpretation, the plane must stand still relative to the ground, because of the way relative velocities work: wheelspeed = groundspeed - beltspeed, so if beltspeed is adjusted to be the opposite of wheelspeed, groundspeed is forced to be zero. In other words, this interpretation only makes sense if you already know that the groundspeed is zero, which is what the whole question is about. If the groundspeed is not zero, this interpretation is impossible because the equation can never be satisfied. Therefore, you must already have answered the question about groundspeed before you can know whether this interpretation is even possible, and so you can't use this interpretation to try to answer the question without going in a logical circle.

So we agree on the final outcomes of our equations....

So sure;

Wheelspeed = Groundspeed - (-Beltspeed)

...I was already assuming that we already knew the belt was going backwards, so I finished off the equation (without showing my work)...

WS = GS + BS

So I guess we don't really disagree there...I thought you were using the above to somehow 'force' the IAS to remain at 0.

From your following post, I believe I can see where we differ.

You seem to think that the above equation (wheelspeed theory) somehow predisposes the GS/IAS to remain at 0. I'm not really sure I follow...

You see, most of the flyboys here will tell you that the plane 'moves' forward because the question 'says it does'. By that measure, they simply 'double the wheelspeed' when the treadmill turns on.

Look, this is the way I solve the equation:
(Given IAS = GS)

WS = GS - (-BS)

'The plane moves 50mph against a treadbelt matching the plane's wheelspeed'

50mph = ?x - (-50)

50mph - (- (-50)) = ?
50mph - 50 = 0mph!!
GS = 0mph
thus
IAS = 0mph
***
This is the way the 'fly Boys' solve the problem, when they assume 'move' means 'airspeed'. This is how they solve for IAS.

'The plane moves 50mph against a treadbelt matching the plane's Airspeed'
Given IAS = GS (calm air, remember?)
WS = GS - (-BS).....waitasecond...who cares? I just said IAS = GS, right? duh!

IAS = GS
GS = 50 (right?)
so,
IAS = 50!!! (yeahhhhhhhh,, I'm sooooo smart...!!!!)

Now, c'mon....you tell ME which one is pre-disposing an answer, and which one is SOLVING for an answer...and which one is just plane DUMB!!!!

It's this simple...if the treadbelt's SURFACE only FEELS 12hp, then it only needs to RETURN 12hp, in order to stop the plane!

The other 88hp from the plane is making the plane 'move over the treadbelt'.
The other 88hp from the treadbelt is making the treadbelt 'go at 50mph under the plane' (...eq's, sic, whatev')

So in order for the treadbelt to RETURN 12hp through those wheels, it must actually SEND 100hp...(because it's loosing 88hp to the wheels)....

I dunno...it may take a bit more vectoring to figure out....

One final note...for all those who want to see the plane 'Move'...

The question dosn't mention the ground or the tower or 'outside observers'...if you really want to get inside this experiment, you need to do 1 thing, and 1 thing only:

GET OFF THE GROUND!!

Get ONTO the Treadbelt, beside the plane! Or get INTO the plane and paint some lines on the treadbelt...

Got it?

NOW, make the plane "MOVE". And at the same time, turn on the treadbelt (remember, now YOU are on the treadbelt).

What say ye, Stu?

Fynlcut

4th April 2006 - 01:37 AM

QUOTE (Atl5p+Apr 4 2006, 12:31 AM)

I don't disagree that a sailboat CAN move up a river...

But what you dissagree with is the sail boat moving faster up current than a prop driven boat.

Such is the prop in the current.
Such is the wheels on the tread belt.
Such is the turbine to the airstream.

Also

The air is to a car as the ground is to the boat and plane.

The air has more to do with the performance of a race car than the ground has to do with the performance of the fastest jets.

Atl5p

4th April 2006 - 01:48 AM

QUOTE (egnorant+Mar 31 2006, 11:33 PM)

'The plane moves 50mph against a treadbelt matching the plane's wheelspeed'

Bruce

Now you're just making stuff up....

YOU said the airspeed MUST be what the plane is moving through, and that the ONLY thing the plane can MOVE through is the air...

Wind Tunnel question, your version of 'MOVES' is the air...so it's wheels should never move...

Just goes to show, it's all in how you view the question...and I still hold that the flyboys version says

'The plane moves though the air....now, does the plane move through the air?'\

You go on, with yo bad self mah man...

Atl5p

4th April 2006 - 01:52 AM

QUOTE (Fynlcut+Apr 3 2006, 08:37 PM)

QUOTE (Atl5p+Apr 4 2006, 12:31 AM)

I don't disagree that a sailboat CAN move up a river...

How many times, and in how many different ways do I have to say this?

I've BEEN there...DONE that....

Sail boat, into a strong current...we didn't get anywhere!

We tucked into a 'counter current'. We started hauling bootay!

Please explain?

sooks

4th April 2006 - 02:29 AM

QUOTE (Atl5p+Apr 4 2006, 01:06 AM)

QUOTE (mr_homm+Apr 2 2006, 02:10 AM)

atl,

you really just dont get it. Yes, the belt only "feels" 12hp. Which also means all the plane feels is 12 hp from the belt. What about all that horsepower being put out through the air which the plane is actually moving through. That is where all the power of the engines is going which is actually moving the plane forward. it doesnt apply its power through the belt to move. the plane is producing umpteen thousand horsepower through the air pushing it forward that the belt has no way of stopping....

Atl5p

4th April 2006 - 02:58 AM

QUOTE (sooks+Apr 3 2006, 09:29 PM)

QUOTE (Atl5p+Apr 4 2006, 01:06 AM)

QUOTE (mr_homm+Apr 2 2006, 02:10 AM)

sooks....plane and belt both make 100hp.

Both 'loose' 12hp to each other via the wheels.

Both speeds are 'equal'.

egnorant

4th April 2006 - 03:25 AM

QUOTE (Atl5p+Apr 4 2006, 01:48 AM)

QUOTE (egnorant+Mar 31 2006, 11:33 PM)

'The plane moves 50mph against a treadbelt matching the plane's wheelspeed'

Bruce

I don't recall saying that...but it can be perfectly valid.
Original question wheel speed version matches this perfectly.
This version FORCES the plane to remain static compared to the inertial starting point.
This relates to the point of power discussion.
In order for it to work the plane will be pushing (on the air) with X at the wheels with the belt providing an opposite force of X at the wheels.

Original question (wheel speed version) has the point that you measure the planes speed against moving away from the inertial starting point.

New question (airspeed version) has the point that you measure the planes speed against moving away from the inertial starting point.

My wind tunnel version still uses a static point for the plane to move against.
My original question "will fly" version uses a static point for the plane to move against.
This static point is the planes own inertial starting point.
This static point coincides with the air, plane, belt and ground as seen at the start of both questions to an outside observer who is also locked into this inertial starting point.
For you to claim that I now measure my planes movement against a different moving point is incorrect.

Any version that has the point that you measure the planes speed against moving against the inertial starting point can result in the plane never moving from the inertial starting point.

Wheel speed version can be simplified.
The plane fails to move through the air...now, does the plane fail to move through the air?
Bruce

Atl5p

4th April 2006 - 03:26 AM

Come to think of it...the question never even mentions wheels, does it? So, why am I even talking about wheelspeed?

The plane really COULD be sitting on it's belly, on the treadbelt. The plane 'moves', and the treadbelt 'matches speed in opposite direction'.

Does the plane fly then?

When the treadbelt is off, the plane can take off normally.

With the plane off, the treadbelt can carry the plane backwards just as fast as the belt moves.

What say ye?

Atl5p

4th April 2006 - 03:32 AM

QUOTE (egnorant+Apr 3 2006, 10:25 PM)

QUOTE (Atl5p+Apr 4 2006, 01:48 AM)

QUOTE (egnorant+Mar 31 2006, 11:33 PM)

'The plane moves 50mph against a treadbelt matching the plane's wheelspeed'

Bruce

That's the point, brucie...this 'static point' you keep reffering to is simply another way of saying 'beltspeed' vs 'groundspeed'.

For example, in the wind tunnel, I can easily say that the 'static point' really IS the air...

and, I've just quoted you not two pages ago...you SAID it:

http://forum.physorg.com/index.php?showtop...indpost&p=76960

QUOTE

The plane contains no mechanism that will allow it to move in any way other than airspeed.

http://forum.physorg.com/index.php?showtop...indpost&p=77378

QUOTE (->

QUOTE

The plane contains no mechanism that will allow it to move in any way other than airspeed.

http://forum.physorg.com/index.php?showtop...indpost&p=77378
...the only way a plane can move itself is in relation to the air..
the only way a plane can move itself is in relation to the air..
and since the only way the plane can move the wheels is to move itself..

So, you've contradicted yourself in the windtunnel...but that's ok...you'll just pick the version that suits you at the time, huh?

Now, how about the wheel-less plane? Any responce there?

egnorant

4th April 2006 - 03:53 AM

QUOTE (Atl5p+Apr 4 2006, 01:06 AM)

The question dosn't mention the ground or the tower or 'outside observers'...if you really want to get inside this experiment, you need to do 1 thing, and 1 thing only:

GET OFF THE GROUND!!

Get ONTO the Treadbelt, beside the plane! Or get INTO the plane and paint some lines on the treadbelt...

Got it?

NOW, make the plane "MOVE". And at the same time, turn on the treadbelt (remember, now YOU are on the treadbelt).

What say ye, Stu?

I tried this...stood on the belt and damn if suddenly the belt had no speed.
And there was this big tailwind that was matching the speed of the plane as it rushed by.
Plane ain't gonna take off with a tailwind matching its speed!!
Plane moves, air moves......belt ain't moving!!!
I looked at the original question and it had the belt moving.
Where in the question does it say the air matches the speed of the plane.
And why ain't the durn belt moving???

Next I tried getting on the plane and suddenly the plane was not moving!!
Belt was whipping by underneath...stuck my head out the window and the air was strangely calm.
Plane ain't gonna take off if it fails to move though the air.
Plane ain't moving, air ain't moving....but the belt was whipping by!!
I looked at the original question and it had the plane moving.
Blowin' smoke out of the window and it just drifts around.
Drop the butt on the belt and the belt moves it away from me backwards....cool!
Thats how I can tell the belt is moving.

This is your proof? I'm having trouble with it.
Don't seem to meet the conditions of the original question....
Hmmmm, it must be wrong then.
Bruce

egnorant

4th April 2006 - 04:10 AM

QUOTE (Atl5p+Apr 4 2006, 03:32 AM)

A static point does not move within the frame of reference.
In the original question the static point can be represented as a point not moving in relation to the air or ground.
Original question makes no mention of these 2 elements moving so this is not a leap of faith.
Once something move against this static point it becomes a moving point as compared to the static point(s).

In the wind tunnel version if you use the moving air as the static point you have the plane moving, you have the wheels moving (not spinning) and you have the ground moving.
This would have the ground matching the planes speed in the same direction and resulting in no wheel speed.
If you had mentioned that the air was not moving and the ground was moving I would have come up with a different answer.
Bruce

Atl5p

4th April 2006 - 04:34 AM

QUOTE (egnorant+Apr 3 2006, 10:53 PM)

QUOTE (Atl5p+Apr 4 2006, 01:06 AM)

uhhhh...did you try standing next to the plane, on the belt? didn't you see the plane MOVE away from you? That's not the wind moving, buddy....that's YOU moving through the calm air (along with the belt).

is that all you've got? It dosn't fly! C'mon over, the water's fine!!

Atl5p

4th April 2006 - 04:37 AM

QUOTE (egnorant+Apr 3 2006, 11:10 PM)

QUOTE (Atl5p+Apr 4 2006, 03:32 AM)

Lemme get this straight...you say the question says this:

'The plane moves though the air'

and then it asks

'Is the plane moving through the air?'

Is that your final answer?

'The plane moves though the air' 'Is the plane moving through the air?' 'The plane moves though the air' 'Is the plane moving through the air?' 'The plane moves though the air' 'Is the plane moving through the air?' 'The plane moves though the air' 'Is the plane moving through the air?' 'The plane moves though the air' 'Is the plane moving through the air?' 'The plane moves though the air' 'Is the plane moving through the air?' 'The plane moves though the air' 'Is the plane moving through the air?' 'The plane moves though the air' 'Is the plane moving through the air?' 'The plane moves though the air' 'Is the plane moving through the air?'

egnorant

4th April 2006 - 05:16 AM

QUOTE (Atl5p+Apr 4 2006, 03:32 AM)

Now, how about the wheel-less plane? Any responce there?

The "wheel less plane theory" just makes utter hash of the wheelspeed theory.
Lets call this the "Frictional Interface Horizontal Separation" theory!! "FI" for short!!
We can even include wheels in this as wheels are a frictional interface as they provide a frictional force for opposing the horizontal separation of the 2 moving elements (plane and belt).

First we assume a range from no friction to infinite friction.
I may even work on negative friction....but not now.
With no friction, say maybe a uniform magnetic levitation with vacuum in the gap.
This may not be actually 0, but for this experiment lets say it is.
Any force the plane produces can only be met with a countering force of 0.

Now we put narrow skids in place of the wheels.
But, we greased up the belt. or had the surface of the belt coated with ice.
Ah, now we have a countering force we can measure!
Lets call it 100 pounds. That is to say that this interface can resist horizontal movement up to a force of 100#. It may increase some as speed increases.
Kinda depends upon the characteristics of the interface element.
Suppose it increases to 300# at takeoff speed and 500# at twice takeoff speed.
As long as the plane is only producing 300# thrust at takeoff speed then we have a plane that does not move from its inertial starting point if the speeds are adhering to the "FI" theory.
At twice "FI" speed (500# opposing force) the plane can only be providing 500# thrust.

Lets get silly here and mount a big rubber pad on the plane and make it of a very sticky tire compound. Experiments show that with the weight of the plane on it it takes a force of 200,000# to make it slide..skid..slip...whatever.
That plane ain't going anywhere.....unless it can provide more than 200k of thrust.
Odd thing about tire rubber is that once it does slide...skid...slip...whatever, it actually requires LESS power to keep it slipping. Makes it tough to keep the plane from moving against the static point.
Lets hope the treadbelt is capable of the same performance.
But if this interface is only capable of 200k of opposing force if the treadbelt is capable of 1,000k we should be allowed to think that the plane is capable of 1,000k also.
Once above 200k the plane is gonna move against the static inertial starting point.

I was going to bolt the plane down on the belt or use a strong cable but this is no longer a friction interface. Then it is just a tug of war.

I like the term "Frictional Interface" as it can be applied to wheels, boat hulls,
skis, mag lev units, or any device that provides a measurable opposing force
between 2 moving elements.

We actually only considered these as a "wheelspeed" theory element as a force that must be countered exactly in order for the theory to work.
Bruce

egnorant

4th April 2006 - 05:28 AM

QUOTE (Atl5p+Apr 4 2006, 04:34 AM)

QUOTE (egnorant+Apr 3 2006, 10:53 PM)

QUOTE (Atl5p+Apr 4 2006, 01:06 AM)

Wait, Am I moving away from the plane or is the plane moving away from me?
For a moment I did consider that I was the one moving when I passed through a cloud of smoke and some A**hole hit me with a cigarette butt.

If you want me to consider the ground, a tower or outside observers you need to let me know...it make for a whole different question.
Bruce

egnorant

4th April 2006 - 05:48 AM

QUOTE (Atl5p+Apr 4 2006, 04:37 AM)

Hmmmm....Tricky!!

I have accepted that as the simplest and most easily workable solutions.
It also fits the most common usage of movement within the framework as presented.

I do like the "wheelspeed" theory as a workable theory as long as you add the
modifier "If and only if the power output of the plane exactly matches the opposing force at the wheels."

The plane moves though the air!...Does the plane move through the air?
Yes!
Kinda simple, but it works for me!

You could also say that the "wheelspeed theory" is asking...
The plane does not move through the air!....Does the plane move through the air?
No!
"If and only if the power output of the plane exactly matches the opposing force at the wheels."
Kinda simple, but it works for me!
Bruce
P.S. I liked the colors on your post...made me smile!

sooks

4th April 2006 - 05:58 AM

QUOTE (Atl5p+Apr 4 2006, 02:58 AM)

QUOTE (sooks+Apr 3 2006, 09:29 PM)

QUOTE (Atl5p+Apr 4 2006, 01:06 AM)

QUOTE (mr_homm+Apr 2 2006, 02:10 AM)

sooks....plane and belt both make 100hp.

Both 'loose' 12hp to each other via the wheels.

Both speeds are 'equal'.

I agree..but equal speed does not equal force.. the plane still has 88hp its using in the air to move forward, much the same the belt has 88hp to move forward.

sooks

4th April 2006 - 06:01 AM

QUOTE (Atl5p+Apr 4 2006, 03:26 AM)

what would you say if the plane was on its belly on the ice (reducing friction coefficient)... Say the plane was very tiny like a cessna... with two giant 747 engines attached. Say the ice is a giant belt able to move... do you think the plane wouldnt move now? youd have the plane just sliding across the ice while the belt slides underneath at the same speed.

Fynlcut

4th April 2006 - 10:12 AM

QUOTE (Atl5p+Apr 4 2006, 02:58 AM)

sooks....plane and belt both make 100hp.

Both 'loose' 12hp to each other via the wheels.

Both speeds are 'equal'.

.......and the plane moves forward and the belt moves backwards, with the 88 hp left over.

You have an equal force from both the plane and the conveyor on the wheels.
The force of the plane is moving the wheels counter clockwise. The force from the belt is moving the wheels counter clockwise. This is by no means equal and opposite. It's not x-x or x+(-x), or how ever you want to say it. It is simply x+x The belt and the plane work together to spin the wheels with 24 hp.
Or the belt and the plane are working in unison to move the wheels with 12 hp, the plane providing 6hp, the belt providing 6 hp. Either way it is a simple addition when talking "force on the wheels"

As far as power = speed. Look at a locomotive, then look at an Indy car, tell me which one has more power and which one goes faster.
(I know thats an extreme and the weight is an issue, but you have already said the plane weighs X amount, the conveyor weighs Y amount+Xamount since the plane is sitting on top of it. So obviously you think the conveyor is aloud to have more power than the plane to reach the "equal speed")

Fynlcut

4th April 2006 - 10:15 AM

QUOTE (Atl5p+Apr 4 2006, 04:37 AM)

'The plane moves though the air' 'Is the plane moving through the air?' 'The plane moves though the air' 'Is the plane moving through the air?' 'The plane moves though the air' 'Is the plane moving through the air?' 'The plane moves though the air' 'Is the plane moving through the air?' 'The plane moves though the air' 'Is the plane moving through the air?' 'The plane moves though the air' 'Is the plane moving through the air?' 'The plane moves though the air' 'Is the plane moving through the air?' 'The plane moves though the air' 'Is the plane moving through the air?' 'The plane moves though the air' 'Is the plane moving through the air?'

The plane and conveyor move at equal speeds, can one move at 0mph?

"get on the conveyor" or "get in the plane"

It doesn't matter what it looks like from the conveyor or in the plane, as the question tells us the speeds are equal.
So if I am in the plane and I see 10 white stripes that are spaced on the conveyor at 1 mile intervals, I know I covered 10 miles. I also know the plane is moving 5 mph forward, and the conveyor is moving 5 mph backwards.

If my plane can produce 64 hp and say as much as 10% of that is used in making the wheels roll. I still have 57.6hp I can fly with.

2 identical planes are flying along at 10,000 feet at cruise speed. The planes are exactly the same, same airframes and powerplants.
One plane holds 6 grown men and 17 gallons of fuel.
One plane holds a small woman and 2 gallons of fuel.
They decide to hold a race to see who will climb to 13,000 feet the fastest. The climb must be at the aircrafts best rate of climb speed. Who wins.
Now they decide to race to 3,000 feet, and can not exceed VNE speed. Who wins?

sooks

4th April 2006 - 02:30 PM

QUOTE (Fynlcut+Apr 4 2006, 10:15 AM)

QUOTE (Atl5p+Apr 4 2006, 04:37 AM)

For soem reason ATL is bent on the fact that the power being transfered through the wheels is the power thats making the plane move forward, and he thinks the power left over is dissapated...not really sure where.

Atl man, you do put up a good fight ill give you that. But i dont really know how else to explain it..or any other examples to give you... its just not how it works. 2 people have just repeated exactly what i said... you still have much more power being exerted that is what propels it forward that youre not accounting for.

My take is that I really think that you may have tried this experiment with your plane and you were able to keep it still. YES, im saying it is possible to keep it still if you can equate the fricitonal force to thrust. But somewehre along the way, your experiment is flawed... (my guess is the lego wheels...and no bearings) but none of us saw waht you did to tell you or see where the flaw lies. I mean, your using a not powerful plane that doesnt even have its own wheels... its just..well not a very concrete experiment. But i believe that you made this stand still and now youre going through any length to prove that experiment.

runner

4th April 2006 - 06:17 PM

QUOTE (Atl5p+Apr 4 2006, 01:06 AM)

QUOTE (mr_homm+Apr 2 2006, 02:10 AM)

So, this is how he admits he's wrong! (without actually saying it) Read what he's been arguing about for the past 5 pages... This statement is such BS! He finally figured out the physics/mathematics conventions and knows he was wrong and cannot explain it away so he tries to say that he was misunderstood, or just not showing his work!

What a load of crap!

A 10 Y.O. understands more about physics & mathematics then he does!

Runner

Fynlcut

4th April 2006 - 06:37 PM

QUOTE (runner+Apr 4 2006, 06:17 PM)

QUOTE (Atl5p+Apr 4 2006, 01:06 AM)

QUOTE (mr_homm+Apr 2 2006, 02:10 AM)

QUOTE

Wheelspeed = Groundspeed + Beltspeed

Where the heck does the planes speed work into that equation?
It is not the ground and the belt that are moving at the same speeds.
It is the plane and the belt.
Wheel speed = belt speed - (-plane speed) 20 = 10 - (-10)
Or wheel speed = ground speed - (-plane speed) 20 = 10 - (-10)

Go back and look and you will see he has been stating
plane speed = belt speed - wheel speed

QUOTE (->

QUOTE

Wheelspeed = Groundspeed + Beltspeed

Using this theory you have
wheels= ground + [or -(-)] belt
10 = 0 + [or -(-)] 10
Duh if the belt is the only thing moving the wheels will turn at that speed.

runner

4th April 2006 - 08:13 PM

QUOTE (Fynlcut+Apr 4 2006, 06:37 PM)

QUOTE (runner+Apr 4 2006, 06:17 PM)

QUOTE (Atl5p+Apr 4 2006, 01:06 AM)

QUOTE (mr_homm+Apr 2 2006, 02:10 AM)

QUOTE

Wheelspeed = Groundspeed + Beltspeed

QUOTE (->

QUOTE

Wheelspeed = Groundspeed + Beltspeed

Using this theory you have
wheels= ground + [or -(-)] belt
10 = 0 + [or -(-)] 10
Duh if the belt is the only thing moving the wheels will turn at that speed.

Groundspeed is not the"speed of the ground" it's the speed of the plane relative to the ground! Same terminology is used in "airspeed"! It's not the speed of the moving air, but of the plane through the air!...

QUOTE

Wheelspeed = Groundspeed + Beltspeed

Groundspeed = Wheelspeed - Beltspeed

Beltspeed = Wheelspeed - Groundspeed

Based on that...

With WS=20, GS=PS=10, BS=-10...

"Wheelspeed = Groundspeed + Beltspeed" -- Incorrect!
20 = 10 + (-10)

"Groundspeed = Wheelspeed - Beltspeed" -- Incorrect!
10 = 20 - (-10)

"Beltspeed = Wheelspeed - Groundspeed" -- Incorrect!
-10 = 20 - 10

now:

"Wheelspeed = Groundspeed(or planespeed) - Beltspeed"
20 = 10 - (-10)

is correct

He was claiming that he was combining the minus signs in his earlier work! And I was calling that a load of crap!

Runner

Atl5p

5th April 2006 - 02:45 AM

Just to be clear, I was responding to a poster's remarks on a little something he called the 'wheelspeed' theory. Thus, 'Wheelspeed' or WS is = Plane.

You can re-read the post if you'd like, it's just on the previous page.

Hope that clears things up for you boys...

egnorant

5th April 2006 - 03:32 AM

QUOTE (Atl5p+Apr 4 2006, 04:34 AM)

I'm still having a little trouble with this one...
The plane is moving because it is sitting on the belt and the planes speed is measured against the belt as spinning wheels.
This is the "wheelspeed" theory as I understand it.

And I am moving too...even while I stand still....while I am on the belt.
The air is NOT moving even as it blows in my face at the same speed the plane went past..because I am moving..while standing still...on the belt.

So while I am standing still on the belt, the plane cruises by at, say, 50 mph.
I also feel a wind in my face due to the air moving at 0 mph.
If I am ON the belt the same as the plane, then my speed is measured as movement on the belt.
Since I am NOT moving on the belt my speed is 0 mph.
Yet the air is also at 0 mph while it fails to flow over the wings of a plane doing 50 mph.

So, the plane is doing 50mph, the belt is doing -50mph, the air is doing 0 mph and I am doing 0 mph!
Still doesn't explain the wind.
Help me out here ATL5P I'm trying to make this work for you.

Bruce

oh come on...

5th April 2006 - 05:16 AM

OK.. so you're on the belt and you whip past the plane at 50mph, feeling wind in your face...proving that the air isn't moving. If you were a block of air being accelerated by the belt and the wing sliced through your neck at 50mph, and your head air travelled over the upper surface of the wing just a bit faster than your body air passes under the wing, this would create a bernoulli effect, causing lift on the wing....but see... this only happens if the belt is accelerating a big bunch of air backwards....which it certainly doesn't, ergo...no flying today in conveyorbeltville because they're all morons. (they're probably all stuck out in the lake on their sailboats trying to move them with a big electric fan from the cockpit)

egnorant

5th April 2006 - 05:34 AM

QUOTE (oh come on...+Apr 5 2006, 05:16 AM)

OK.. so you're on the belt and you whip past the plane at 50mph, feeling wind in your face...proving that the air isn't moving. If you were a block of air being accelerated by the belt and the wing sliced through your neck at 50mph, and your head air traveled over the upper surface of the wing just a bit faster than your body air passes under the wing, this would create a bernoulli effect, causing lift on the wing....but see... this only happens if the belt is accelerating a big bunch of air backwards....which it certainly doesn't, ergo...no flying today in conveyorbeltville because they're all morons. (they're probably all stuck out in the lake on their sailboats trying to move them with a big electric fan from the cockpit)

Thank you for proving that the air isn't moving at a different speed than the plane.
I have been trying to click into a "moronic" mind set to help understand some of this.
Pain meds seem to hinder the process.
Nothing on TV seems to accelerate the process. (In relation to the normal learning process).
I'm was about to take a jet engine to blow on a sail, but I could only find a small rocket motor......and the boat is at my brothers.
Bruce

..tried it..

5th April 2006 - 06:15 AM

jet or rocket engine aimed at sail is no good... you get some fair speed toward the stern though, and that's good because you don't want the melting Dacron sail falling in your lap...that just burns in ways that Amoxicillin won't help

sooks

5th April 2006 - 07:13 AM

QUOTE (oh come on...+Apr 5 2006, 05:16 AM)

Wouldnt be your body passed below the wing faster than your head passes over the top of the wing... wouldnt that be the bernouli effect?

Atl5p

6th April 2006 - 04:21 AM

QUOTE (egnorant+Apr 5 2006, 12:34 AM)

QUOTE (oh come on...+Apr 5 2006, 05:16 AM)

OK.. so you're on the belt and you whip past the plane at 50mph, feeling wind in your face...proving that the air isn't moving. If you were a block of air being accelerated by the belt and the wing sliced through your neck at 50mph, and your head air traveled over the upper surface of the wing just a bit faster than your body air passes under the wing, this would create a bernoulli effect, causing lift on the wing....but see... this only happens if the belt is accelerating a big bunch of air backwards....which it certainly doesn't, ergo...no flying today in conveyorbeltville because they're all morons. (they're probably all stuck out in the lake on their sailboats trying to move them with a big electric fan from the cockpit)

I'm sure I don't know what's so difficult to understand...You are standing on the same surface as the plane...the air is calm...the plane 'moves forward' from your perspective at 10mph...at the same time, the wind hits your BACK (not your face), at 10mph...(a 'calm' air molecule is watching you speed backwards, along with the belt)...

Have I made it clearer now? Does the plane fly in the above scenerio? Of course not! It's called the 'wheelspeed theory' by one of your 'fly boy' brothers...but for some reason, even he thinks it will still fly.

yesitdid

6th April 2006 - 04:46 AM

This thread is almost as bad as the WTC thread. No, check that. It is worse for going round and round(pun fully intended) since it involves only one subject.

The plane will fly, accept it.

Resistance is futile.

newton

6th April 2006 - 04:50 AM

QUOTE (yesitdid+Apr 6 2006, 04:46 AM)

except that, in this arena, you and i agree one hundred percent.

you may want to chew out that dunce, arthur, though.

Atl5p

6th April 2006 - 04:56 AM

QUOTE (yesitdid+Apr 5 2006, 11:46 PM)

now that was insightful...typical though!

egnorant

6th April 2006 - 05:39 AM

QUOTE (Atl5p+Apr 6 2006, 04:21 AM)

O.K. The plane is going 10 mph.
The plane speed is measured as it passes over the belt because it is sitting on the belt.
I am passing over the belt at 0 mph.
My speed is 0 mph because I am sitting on the belt!

The air is also moving at 10 mph as a tailwind...over the belt.

From my perspective the plane and the air are moving but the belt and I are not!
Of course a plane with a matching tailwind won't fly.
From my perspective the belt ain't moving!
Bruce

Fynlcut

6th April 2006 - 09:07 AM

QUOTE (egnorant+Apr 6 2006, 05:39 AM)

QUOTE (Atl5p+Apr 6 2006, 04:21 AM)

It appears the belt its not moving, but in reality the belt is the only thing moving.

egnorant

6th April 2006 - 06:39 PM

QUOTE (Fynlcut+Apr 6 2006, 09:07 AM)

QUOTE (egnorant+Apr 6 2006, 05:39 AM)

QUOTE (Atl5p+Apr 6 2006, 04:21 AM)

It appears the belt its not moving, but in reality the belt is the only thing moving.

Thats what I have been trying to figure out.
Since the ground, tower,observers have been disallowed, either the plane AND the air are moving or the belt AND I are moving.
It seems as if the explanation given has the plane given a speed, the belt given a speed and me standing on the belt given a speed. While the air has no speed!

This is the flaw of the wheelspeed theory.
Arbitrary choice of reference points is an interesting diversion, but once used can
be shifted to prove or disprove any version that comes along.

The argument has been made that the planes speed is measured at the wheels due to the fact that it is sitting on the treadbelt.
Then it was presented that an observer, while also sitting on the belt,
had speed because he was moving at the same speed as the belt.
Something that moves over the belt has speed the same as something that doesn't move over the belt has speed. Doesn't work!

Wheel speed version a.k.a frictional interface version a.k.a. multiple reference point version only work once you start adding at least 2 carefully balanced variables.

I was waiting for someone to start claiming that a plane trip from New York to L.A.
is actually the length of 2 runways because the wheels only measure that distance.
Or maybe a car doing a burnout is going just as fast as one that isn't because the wheels are moving the same speed.

Just fighting silly with silly!

Bruce

Atl5p

7th April 2006 - 02:01 AM

The point of refrence is the same for both the plane and the treadbelt:

'Whatever the object's weight is resting against, is it's point of inception'

I'll be the first to admit, it pretty much just boils down to a difference in opinion as to where the speed of the plane is measured against.

Anyway, I like the 'wheelspeed' version better because it gives relevence to the treadbelt.

The 'airspeed' theory completly ignores the treadbelt. It just says 'The plane moves through the air....Does the plane move through the air?'
Nah, dosn't interest me...thanks anyway!

SNLS

7th April 2006 - 03:13 AM

QUOTE (Atl5p+Apr 6 2006, 04:56 AM)

QUOTE (yesitdid+Apr 5 2006, 11:46 PM)

now that was insightful...typical though!

More insight then you'll ever have!

You keep draggin this topic in circles with your theories from the lunatic fringe!

egnorant

7th April 2006 - 06:09 AM

QUOTE (Atl5p+Apr 7 2006, 02:01 AM)

Agreed that the wheelspeed theory is fun and requires a lot of twisting to make it work.
I took a long time to actually convince MYSELF that it would work. I began my rants with the premise that the plane had to move FIRST through the air!

Even you could make a good argument that the belt may actually rest on wheels or rollers. This would have the belt moving at 0 mph in relation to the wheels of the conveyor. Point of inception kinda thing.
Gets real complicated when you realize that the axle of the plane runs on bearings
that may be at a totally different speed.
Might work if the belt were just dragged along the ground somehow and not supported and moved by whatever it was sitting on.

This also begs the question, What is the air sitting on.
Is the air on the plane going 0 mph in one direction while the air on the belt is going 50 mph in the same direction? Or is it the opposite direction?
Why not measure it against the item above it or between points that touch...or don't touch, or where they place their power or use the average of the other moving element and the other elements point of power.
Consider one set of different points you gotta consider them all.

"Will fly" version (single speed reference point) understands that the belt IS largely irrelevant.
It exist to give the wheels (or skids or whatever) an additional speed component.
The question of power or friction or the 100 other things that have been ADDED to the formula are not needed to make it work.
The only assumption that must be made is that the plane and the belt are mechanically capable of reasonable performance.

"Wheelspeed" version (plane to belt and belt to ground speed reference points) CAN be used to make the plane not fly. But only if applied in specific ways and it adds power and friction variables.

I almost called the last paragraph "variable speed point references".
Then I remembered that most of the variable versions actually fly!
There is the point of power version....
Plane speed to air and belt speed to ground... It flies!
Or the reverse (kinda redundant since we have agreed that air and ground can actually constitute the same point)
Plane speed to ground and belt speed to air.....flies!
Plane speed to air and belt speed to plane....flies!
Plane speed to belt and belt speed to plane...not enough info call it 50/50.
Half of this version can have the plane moving through the air and the other half has it actually moving backwards through the air.
Plane to belt and belt to ground (or air) .....NO Fly!!
The only versions that don't fly are the ones that insure that the plane does not move through the air!
So....If the plane does not move through the air....Does the plane move through the air?

Nah, doesn't interest me....thanks anyway!

Bruce

Fynlcut

7th April 2006 - 12:08 PM

Yep

Still don't know how the wheels will move if the plane never moves, unless the conveyor is the only thing moving, and the plane is simply remaining stationary. Can a stationary plane fly?

egnorant

7th April 2006 - 05:46 PM

I had a lot of trouble with that for a while.
But finally it hit me that the way it did work was that the term EXACT was the key.
And it worked only if you measured the planes speed at the wheels.
This makes the plane largely irrelevent, only the wheels are used.
And it worked if the force the plane applied to the air was matched EXACTLY by
the drag at the wheels in the opposite direction.
This could also be accomplished by a rope holding the plane back or a mount to the ground via tha axles.
We drew a diagram that looked like a clock face with top half being the plane and the bottom half the wheels.
9 was infinite force left , 3 was infinite force right, 12 was 0 for the plane and 6 was
0 for the wheels.
As long as the dials were an exact straight line (11 indicated for the plane would be 5 indicated for the wheels) the wheelspeed theory would work.
You gotta be very specific and allow for performance limits .
Otherwise this could become a philosophical question similar to the irresistible
force meeting an unmovable object type of question.
That gibberish that ATL5P was spouting about 100 hp being successfully opposed by 12 hp to equal 0 is simply wrong.
But that is just his way...workable theory with non-workable explanations.
Bruce

Atl5p

8th April 2006 - 01:06 AM

QUOTE (egnorant+Apr 7 2006, 12:46 PM)

QUOTE

This makes the plane largely irrelevent, only the wheels are used.

Uhh, what about the engine and prop? I'm sure I don't understand why you feel the plane is irrelevent.

QUOTE (->

QUOTE

This makes the plane largely irrelevent, only the wheels are used.

Uhh, what about the engine and prop? I'm sure I don't understand why you feel the plane is irrelevent.

And it worked if the force the plane applied to the air was matched EXACTLY by
the drag at the wheels in the opposite direction.

Nooo, the force of the plane is matched by the force of the treadbelt.
The force that the wheels apply to the belt (it's CRF) is matched by the belt's CRF in the opposite direction.

QUOTE

And it worked if the force the plane applied to the air was matched EXACTLY by
the drag at the wheels in the opposite direction.

I hope you don't see a problem with this (?)

QUOTE (->

QUOTE

And it worked if the force the plane applied to the air was matched EXACTLY by
the drag at the wheels in the opposite direction.

I hope you don't see a problem with this (?)

That gibberish that ATL5P was spouting about 100 hp being successfully opposed by 12 hp to equal 0 is simply wrong.
But that is just his way...workable theory with non-workable explanations.

Not sure where you got that...it's not what I said at all...

swimmer

8th April 2006 - 01:34 AM

In the spirit of ATL5P...

If we are going to accept that the wheel speed should be measured relative to the conveyor surface, I think we should consider measuring the speed of the conveyor relative to the speed of the wheels. We have all assumed that the wheels are not skidding so measuring the treadbelt speed relative to the wheel surface seems the thing to do - they are in direct contact, after all.

This also has the advantage that in this "symmetrical frame of reference" the treadbelt never moves at all and neither do the wheels' surface.

The plane will still fly tho...

Atl5p

8th April 2006 - 02:04 AM

QUOTE (swimmer+Apr 7 2006, 08:34 PM)

So, swimmer, did you ever figure out if the car would gain IAS? Or would the car just sit there at 0 IAS? 'The car moves forward' right? Which way is it going to be?

I think that we can all agree that the wheelspeed method will cause the plane to remain at 0 IAS. But you guys don't like a 'wheelspeed' version for various reasons.

So, please...once again...will the car gain any IAS, if the word 'car' is replaced with the word 'plane'?

swimmer

8th April 2006 - 05:22 PM

QUOTE (Atl5p+Apr 8 2006, 02:04 AM)

QUOTE (swimmer+Apr 7 2006, 08:34 PM)

ZZzzzzzzzzzzzzzzzzzzzz....

Car's thrust is delivered via its wheels pushing against the "ground".

Plane's thrust is delivered via its propeller/jet pushing against the air.

That's the difference.

Many moons ago I supposed two cars, one front wheel drive the other rear wheel drive. If both of the cars only have their front wheels on the treadbelt and their rears wheels on terra firma...

...by your logic neither car would be able to drive forwards. I don't think so.

FWD car would be "immobile, the RWD wouldn't.

Craigx

9th April 2006 - 12:56 AM

Forgive me for not reading through 300+ pages here but I noticed in the first few that many people answered incorrectly.

The plane will NOT take off. It does, as others have said , need wind traveling through the wings. The wheels of the airplane are only there so it isn't a bumpy takeoff.

In the USAF I've seen countless engine tests on the ground with afterburners blazing,"B2 bombers". The brakes on the wheels keep it from moving FOREWARD and it doesnt try to take off into the air from a stationary position. Usually they also chain the aircraft to the ground so it won't move foreward incase the brakes fail but this in no way would keep the aircraft from going upwards if a 300mph wind hit the front of it.

swimmer

10th April 2006 - 12:22 AM

QUOTE (Craigx+Apr 9 2006, 12:56 AM)

Maybe you should go back and read a few earlier posts - just not ALT5P's

Craigx

10th April 2006 - 01:00 AM

Your right.

The engines thrust literally"suck" the plane through the air. The free spinning wheels would have no effect on this.

COnsider my position reversed.

gerald

10th April 2006 - 03:47 AM

Assuming there was no prop or jet engine, am I right in thinking that it would not take off? That is to say, if the only way the plane achieved enough lift to fly was by having its wheels move it at a certain speed relative to the ground, wouldn't it stay stationary on the conveyor?

egnorant

10th April 2006 - 04:13 PM

QUOTE (gerald+Apr 10 2006, 03:47 AM)

In order for it to take off the plane must move through the air.
The question has been interpreted as ground speed = air speed.
Fact is that the hub of the wheel must have sufficient ground speed (air speed)
in order to take off. Wheel hub and wings are in the same frame of reference.
So hub speed = wing speed.
As long as the hub (wing) has ground speed (air) sufficient for lift off it will fly.

You need to reread the original question and decide how the plane moves.
If you take out an engine you still must provide for a mechanism for the plane to move.

One current version uses the plane as a device for providing the force to be countered through the wheel by the treadbelt.
This could be accomplished by any use of a force that acted upon the air or ground.

With no prop or jet the plane would stay stationary on the belt and the belt would have 0 speed relative to the ground. Nothing moves.
Bruce
P.S. Local group got our hybrid car moving this weekend.
Anyone have an idea for better batteries (cheap)?

swimmer

12th April 2006 - 09:59 PM

...I'm still waiting for the results of the force measuring experiment I suggested ATL5P....

And what's your take on my earlier question:

Two cars, one front wheel drive the other rear wheel drive. If both of the cars have only their front wheels on the treadbelt and their rears wheels on the ground

...by your logic neither car would be able to drive forwards.

I think you are wrong - in fact the FWD car would be "immobile" relative to the road but the RWD wouldn't - it would move forward and the conveyor/treadbelt could little about it.

dapascha

12th April 2006 - 10:19 PM

QUOTE (swimmer+Apr 12 2006, 09:59 PM)

...I'm still waiting for the results of the force measuring experiment I suggested ATL5P....

QUOTE

I think you are wrong - in fact the FWD car would be "immobile" relative to the road but the RWD wouldn't - it would move forward and the conveyor/treadbelt could little about it.

... well, except just stay where it is. The RWD car would move a few feet, untill it's rear wheels will reach the conveyor belt after which... yada, yada, etc.

But maybe I'm nitpicking. In general I agree, of course.

I'll leave now.

(the plane will take off!)
dapascha

swimmer

24th April 2006 - 11:07 PM

Is the "flying" parrot deceased?

egnorant

25th April 2006 - 03:33 AM

Seems like it. I was about to invite ATL5P and others over to the Flat Earth Society
forums for a good old fashioned logical brawl.
Niece got sidetracked when I put an additional 12 volts to her electric scooter.
I hid the batteries in an old propane torch bottle and put a NOS sticker on it.
Plumbing and a big red button marked TURBO caused the local boys to laugh until she blew past on "full boost".
Bruce

Atl5p

2nd May 2006 - 04:23 AM

Just checking in every once in awhile, to see if there is any intelligent life remaining.

Folks, the topic is dead...it's all in how you view the question. I do not prefer the 'the plane moves though the air...does it move through the air' version...simple as that.

However, it also appears that everyone is in agreement...if the speed of the plane is determined via 'treadbelt speed', then the plane will have 0 IAS when the 'speed' of the plane 'matches' the speed of the treadbelt (or visa versa for the sticklers.

And that just renders silly, all those long drawn out arguments about how the plane can't fly because:
the wheels are freewheel'in,
there isn't enough force passed through the wheels to stop the plane
the plane isn't driven by the wheels, so that has something to do with anything,
a sailboat can move upstream, while an otherwise equal speed propeller boat cannot,
and I'm sure there are many more....they are all bunk.

For example, if the plane can move up the treadbelt, (due to it's movement through the air), then why dosn't the car move up the treadbelt, (I'm saying it moves, so it moves!)

Anyway, it was fun...I'll keep checking in to see what's going on, from time to time...don't worry...

egnorant

2nd May 2006 - 01:40 PM

QUOTE (Atl5p+May 2 2006, 04:23 AM)

While it is true that there are different viable viewpoints, you continue to try to argue against those who choose otherwise.
The items you call "Bunk" are much more practical and workable than the "wheelspeed" theory.

Your pet "wheelspeed" theory is still the shakiest scenario around.
I personally maintain that the belt is the only thing moving in the wheelspeed scenario. Kinda like the paper being passed through a copier! I am one of those who are NOT in agreement with your claim about treadbelt speed.

All who have watched this thread realize that the listed items are not bunk.
You dispute them because they disprove your "pet" theory.

Plane verses car scenario is the same in theory...just different in the mechanics!

Welcome back! I was afraid you may have given up!
You still need to check out The Flat Earth Society web page.
But I could understand if you would rather be a jester at the palace rather than just another ignorant peasant!
Bruce

sooks

3rd May 2006 - 02:21 PM

QUOTE (Atl5p+May 2 2006, 04:23 AM)

atl,

It doesnt matter what you based the speed of the plane off of. I dotn know how many times ive said this. But wahtever you base the speed of the plane off of, to compare it with the treadbelts speed, the treadbelt must be based off the same thing. Otherwise youre comparing apples to oranges. But i agree there is room for a different view in that if the treadbelt is being matched to wheel speed or plane speed and youll get different answers there.

yesitdid

3rd May 2006 - 05:41 PM

Thread is still going eh?

Plane takes off!

swimmer

5th May 2006 - 12:40 AM

QUOTE (Atl5p+May 2 2006, 04:23 AM)

Fun? It wasn't fun!

It was like trying to explain evolution to a scientifically illiterate creationist.

Talk about a lack of communication...

... and you still don't get it - Hah!

Roland

6th May 2006 - 12:33 AM

Question:

If you are running on a treadmill while wearing a jet pack and you hit the forward blaster control on the jet pack would you speed the treadmill up with the extra power or would you go shooting off the treadmill into the nearest wall?

If you can answer this question, then the airplane on a conveyor should be easy!

Betelguese

12th May 2006 - 05:49 PM

if the plane really could take off wouldnt this make airports a lot lot smaller.. like just the size of the planes and a bit more would be needed for each take off.. and if the thrust of the engine on the surrounding independent air is enough then its vertical take off.. but thrust is what makes the plane go forward.. and the conveyor belt is going backwards.. so its nullifie.. according to me the plane definitely wont take off

Dave Grossman

13th May 2006 - 12:21 AM

It's really very simple. If we assume that the wheel bearings have no friction then the motion of the runway will not move the plane at all (edit: actually, that would only be true at constant velocity. as the conveyer accelerates, there should be a force on the bearing but it would not be very large). Even with a moderate amount of friction, the force on the plane would be small and would be insignificant when compared to the thrust of the engines.

The plane will take off.

- Dave

Noooo!

13th May 2006 - 01:05 AM

This

Thread

Just

Won't

Die!!!

Dave Grossman

13th May 2006 - 02:57 AM

QUOTE (Noooo!+May 13 2006, 01:05 AM)

This

Thread

Just

Won't

Die!!!

That's the beauty of it.

It is within our rights as posters to respond to a thread without having read any of the previous responses and to have simply scanned the first paragraph of the original post or to have simply have read the subject line.

- Dave

Fynlcut

15th May 2006 - 12:58 PM

QUOTE (Betelguese+May 12 2006, 05:49 PM)

1) Why would it make airports smaller?
2) The ground is normally moving backwards, relative to the plane, during take off. How fast depends on the amount of wind the plane is taking off in. Sometimes it moves faster than other times, and doesn't make a lick of difference other than the amount of ground covered prior to lift off.
You don't take off down wind, simply because you might run out of runway prior to lift off, not because it is impossible.
3) If it takes 4# of thrust to move a plane (read rotate the wheels of a plane) on a static runway, how much thrust is needed to move the plane when the runway is moving back wars? How much thrust if the runway is moving forwards?
4) Some people say they talk to the dead, and I don't believe them either.

prospect47

19th May 2006 - 03:53 AM

QUOTE (dirak+Jul 19 2005, 09:53 AM)

A plane is standing on runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the plane speed and tunes the speed of the conveyor to be exactly the same (but in opposite direction).

The question is:

Will the plane take off or not? Will it be able to run up and take off?

The aircraft landing gear are free rolling. The aircraft is not propelled by the wheels. It would be more of an impossibility to have a conveyor able to match the speed of the free rolling wheels. The aircraft would take off because the aircraft is pulling itself threw the air independent of the wheels. The wheel speed would be airspeed plus conveyor speed. Airspeed could not be removed from the wheel speed equation.

battlepope

19th May 2006 - 06:54 AM

for those that think the belt will keep the plane stationary; if that were correct then the "conveyor belt" would not move at all, seeing as it's supposed to be matching the speed of the aircraft in question.

Guest_Jason

22nd May 2006 - 09:26 AM

Any of you that think this plane won't take off are a disgrace to this forum, and would be better suited to a child's paint by numbers course.

l4zy

22nd May 2006 - 10:18 AM

QUOTE (Guest_Jason+May 22 2006, 09:26 AM)

Any of you that think this plane won't take off are a disgrace to this forum, and would be better suited to a child's paint by numbers course.

the plane takes off...if you dont agree with that you should DIAF

the question is worded in a way to confuse you...the conveyor cannot effect the speed of the plane relative to the ground, the wheels just spin and spin

wheel speed = speed of conveyor + speed over ground

it doesnt matter how fast the conveyor goes...

NeoDude

24th May 2006 - 06:02 PM

It all depends on which situation you are talking about.

If the belt matched the planes airspeed then yes, it would be able to take off.

If the belt matched the wheel speed (Ground Speed) then no, it wouldn't budge an inch.

sooks

24th May 2006 - 06:28 PM

If it matches the wheel speed..both the wheels and belt will almost instantly be going infinately fast and it becomes a paradox... but would be moving forward slightly as the center of mass is being "pushed" from the engines.

NeoDude

24th May 2006 - 06:30 PM

QUOTE (sooks+May 24 2006, 06:28 PM)

It would not reach infinity. A point would be reached where the friction in the wheels would exactly balance the force from the engines.

Boeing Engineer

25th May 2006 - 06:04 AM

For Your Information,

The question is poorly worded.
However the plane will not take off.

A plane is merely a motor vehicle with wings, powered not by a drive shaft connected to the wheels but by an engine mounted on the chasis/fuselage.

As the engine, suppose on the back of a ute powers the 'plane' the plane tries to move forward. The conveyor moves backwards and stops the plane moving forward. A car or a plane on a conveyor (in neutral) will move in the direction of the conveyor. A person on rollerblades will move in the direction of the conveyor.

The only argument against this happening is the wheels are free spinning or there is not enough force exerted on the plane. But the question states that the conveyor matches the planes 'speed' (A Bad Word)

The thrust approaches infinity as does the conveyor, however there is not any air passing over the wings, only an infinite amount going through the jet engine.
Unless the plane can move relative to the groun and hence the air around the ground/conveyor it can not take off.

This is an elementary problem posed to 1st year aerospace engineers and a clear answer was given. The plane can not take off!

If you are going to disagree with this, please state clearly why and I will give a clear response.

another guest

25th May 2006 - 10:10 AM

QUOTE (Boeing Engineer+May 25 2006, 06:04 AM)

if you really are a boeing engineer, i'm never flying on a boeing again

'the planes speed' can only ever mean the motion of the plane, not the rate of spin of the wheels
how does the conveyor moving backwards 'stop the plane'? by increasing the drag on the wheels? but these wheels are free spinning (erm, like all wheels)

imagine the plane being fitted with low-friction skids, it moves forward, the belt moves backwards, so what, the plane moves forward and eventually takes off

yeehaw

25th May 2006 - 10:25 AM

QUOTE (Boeing Engineer+May 25 2006, 06:04 AM)

This is an elementary problem posed to 1st year aerospace engineers and a clear answer was given. The plane can not take off!

If you are going to disagree with this, please state clearly why and I will give a clear response.

very interesting - as when we did it, the answer came out as yes...

could I ask how your sight of the question was worded, as in ours it was that the aircraft was MOVING in one direction, the conveyor reacted by moving in the opposite direction at equal speed.

By standard English definition of the question, the fact that it is stated that the plane is moving in a given direction before reference to the conveyor, it is inferred that the comparison point for the speed of the aircraft is global, outside and irrespective of the conveyor belt, as it would be in everyday life.

That given, the wheels and wheel speed become irrelevant. We are relying on the engine thrust acting globally as normal - against the air around it. The only relationship between the aircraft and the conveyor belt is the wheels and substructure. It could be argued that these components would be incapable of the increase in loading due to the velocity of the wheel being a factor twice that of it's speed relative to ground effect, however that is purely speculative, the point of the question is to make you consider if the plane will gain forward motion, the major requirement of lift, of which the answer is yes, it will.

To take your position, with the wheels as the global, is frankly somewhat surprising as the question cannot maintain it's own stated conditions. The engines would not be able to be turned on before the conditional precedence of the question were no longer attainable.

Were the wheels powered, then indeed you would be correct, but they are not. The only influence on the wheels rotation is the friction between the surface and the tyre, transposed from the linear movement of the axle created by the engines thrust giving forward motion. To infer as you have that the wheels speed is relative to the conveyor means that equilibrium is achieved only when the aircraft is sat there, motionless, without the engines running.

Tim

25th May 2006 - 12:11 PM

Now this is scary. I thought people on a Physics forum would have some common sense. As for the 'Boeing engineer', boy I hope that is just a made up name.

The question clearly states

QUOTE (dirak+Jul 19 2005, 09:53 AM)

A plane is standing on runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the plane speed and tunes the speed of the conveyor to be exactly the same (but in opposite direction).

The question is:

Will the plane take off or not? Will it be able to run up and take off?

So, the plane moves west @ 10kts. The conveyor moves East @ 10kts. The tyres turn at 20kts

The plane moves west @ 100kts, the conveyor moves east @ 100kts, the tyres turn @ 200kts (so what, this is a theoretical question, if you can make a concrete conveyor and power it, you can make uprated tyres.

As soon as the airspeed passes take off speed, YES the aircraft takes off. Only difference is the tyres spinning double normal speed, and slightly more thrust needed to offset that extra drag.

Sorry I have not read the whole thread, I'm sure this has already been said before.

Tim

25th May 2006 - 12:20 PM

hmm no edit button?
Forgot to add to my post above, I believe BE was right on one thing, I have heard that 'This is an elementary problem posed to 1st year aerospace engineers', designed to catch those who can't think past wheel driven vehicles. Those who have an understanding of plane motors or thrust will usually be able to arrive at the correct answer.

krreagan

25th May 2006 - 01:55 PM

QUOTE (Boeing Engineer+May 24 2006, 11:04 PM)

Sanitation Engineer?

One word "FORCE"! How does the belt apply enough force to the plane to counter the force of the engines! After all wheels were invented to reduce friction to a minimum! This has been asked though out this thread and nobody has put forth a reasonable explanation.

All speed in this problem is relative to a stationary observer! (one standing on the tarmac). Read the question posed, it states the plane moves in one direction and the belt in the opposite direction. They both move relative to the observer! the only reference frame in which this condition is met, is that of the ground (or air).

Krreagan

egnorant

25th May 2006 - 03:38 PM

QUOTE (Boeing Engineer+May 25 2006, 06:04 AM)

The question is poorly worded.

As the engine, suppose on the back of a ute powers the 'plane' the plane tries to move forward. The conveyor moves backwards and stops the plane moving forward. A car or a plane on a conveyor (in neutral) will move in the direction of the conveyor. A person on rollerblades will move in the direction of the conveyor.

The only argument against this happening is the wheels are free spinning or there is not enough force exerted on the plane. But the question states that the conveyor matches the planes 'speed' (A Bad Word)

Your claim of a poorly worded question may be valid.
But changing the wording to support your case is not a valid method.

Your explanation starts with you stating that the "Plane TRIES to move".
Nope..it is stated that the plane DOES move.

You then add the phrase "The conveyor moves backwards and stops the plane moving forward".
Remove the word "stops" from this and look at the question again.
(O.K. change moving to moves also, like the question states.)
Backwards and forwards are O.K. as they accurately reflect the question.

Look at this one... "A car or a plane on a conveyor (in neutral) will move in the direction of the conveyor".
Nowhere is this stated in the question. In fact it clearly states that the plane DOES move...in the OPPOSITE direction.

SPEED is not a "Bad word". It is simply a formula for us to use.
Distance and duration..
Miles per hour is the one I used. Kilometers per hour, feet per second, light-years per century...take your pick!

The plane and the conveyor have 3 possible states of movement...forward, backward and stop (Using your words).
Plane moves one direction (forward), conveyor moves the opposite direction (backwards). Stop is not the opposite direction of either of these!
Let's check some of your statements!!

"The conveyor moves backwards and stops the plane moving forward"
Conveyor=backwards....plane = stop. Sorry, invalid!

"A car or a plane on a conveyor (in neutral) will move in the direction of the conveyor".
conveyor=backwards....plane = backwards. Wrong again. Invalid as applied to the question.

If you are truly a Boeing engineer please state your system qualifications.
I suspect it may be in the field of In-flight nutrition.
I claim no qualifications other than the correctness of my arguments.
Bruce

Ensa

25th May 2006 - 04:11 PM

QUOTE (Ensa+Nov 7 2005, 06:14 PM)

If there were no friction in the wheels the entire energy of the conveyor would be tranformed into the angular momentum of the wheels. The velocity of the plane would be unaffected by any motion of the conveyor and the plane would move forward as if the conveyor didn't exist.
Also if the reference frame of the system is the surface of the conveyor (as some have suggested) then given some more weird assumptions the conveyor would accellerate as fast as it could. Because of E=mc^2 there would be nothing to stop the mass of the wheels increasing until they collappsed to form black holes thus sucking the whole terrible thought experement into un-observability... (I wish)
So
1. If there were no friction in the wheels the plane would move forward and take off (unless it were destroyed by the said demise of the wheels), all the energy from the jet or whatever would be transformed into forward motion and blah blah the conveyor has no effect other than to increase the speed of the wheels rotation.
2. If there were friction in the wheels then the outcome depends on how much friction and what the reference frame of the system is.
2a.If the reference frame of the system is the observer mentioned in the post and the wheels have normal friction (seems reasonable) then the plane takes off but the wheels rotate twice as fast as if there were no conveyor.
2b.If the reference frame is the surface of the conveyor (??) then again if the wheels are capable of coping with the accelleration of the conveyor without seizing the the plane would probably take off.
If the wheels seize then depending upon other assumtions then the plane would either stay still or move backwards.

I don't think I have left anything out.

Looking at this thread again, I wonder what responses people have to my post from page 11, which I thought summed it up at the time.
There have been a variety of sane and insane answers to the original question, I pick my earlier post just to see how my response to feedback has changed since then, not because it is neccesarily better than any of the others.
I look forward to seeing reponses to my previous points if anyone is so kind, so I can form new answers.
Ensa.

birdman

26th May 2006 - 04:01 AM

i thought of it like this, and i don't know if i'm entirely correct

but if a jet without its engines running were on a converyor belt

|plane|
<-------------------

and the conveyor is going in the direction show by <----
the plane's speed would be that of the conveyor in the left direction

(now consider the problem in reverse)
the plane has a system to match the speed of the conveyor

so the plane thrusts to the right so that its speed, relative to the conveyor is the same. So relative to the ground its "velocity" is zero.

In this situation the plane will not take off.

Final Answer

26th May 2006 - 04:16 AM

For The Question Asked, And Re-Stated Several Times.

The Plane Will Take Off, Because the conveyor's belt moves in the opposite direction to the plane. This provides some resistance to the plane (approximately F=uMg where u is the co-efficient of kinetic friction, M=mass of the plane, g=9.8ms-2) by not enough to counter thrust.

For those who are still not convinced the plane can take off, you are simply misunderstanding the question as i did for many sleepless nights

If the plane has speed, it is moving (i would have prefered the use of the word velocity as implied by a moronic Boeing Engineer)

If the conveyor moved at a scalar*planes thrust (not speed) such that the conveyors movement combined with the friction of the wheels could hold the plane still, then the plane would not take off (it is stationary=no lift)
However this is highly unlikely to occur. Approximate speed of conveyor would be close to that of the spaceship in SpaceBalls. (ludicrous)

joedawson

26th May 2006 - 05:43 AM

I understand that the plane will take off.

But could someone explain this to me. Preferably someone who's argument is all about "relative to the outside environment".

If a man is on a conveyor belt, or a treadmill. And his speed is tracked and matched by the conveyor...(same as the plane problem)

Will the man move forward?

According to some arguments for the plane taking off, the man will move forward.

Because he has speed forward (stated), the conveyor matches this backwards, which holds him stationary relative to the outside env.(?).

It should not matter by which means he moves forward to gain speed. because it is stated that he is moving forward at a speed.

I don't even know if I'm making sense but it was just a thought.

Fallen

26th May 2006 - 08:42 AM

The plane will take off. The planes engines do not work in the same maner as does a car or a person running on a treadmill. A car or person gain thier propulsion by friction on the ground a plane does NOT. A planes engines work on the air and the tires of the plane are to reduce the friction, they do however produce drag. A plane on a treadmill will have increased drag from the speed of the treadmill and will simply need to correct for this by using more thrust. The relative ground speed of the plane bears nothing at all to the wind speed of the plane. A featherlight personal aircraft designed to take off at 50mph WINDSPEED can take off standing still on the ground of the headon wind is at 50mph or greater.

Therefor the treadmill in the question only affects the speed of the tires spin and a slight increase in drag, but the plane will still move and by compensating for the extra drag will still be able to achieve the proper wind speed for takeoff. In a similar maner a plane can still take off with massive tailwind.

This is a simple problem with an obvious answer if you look at how a plane functions.

Hairnet

26th May 2006 - 09:20 AM

THE PLANE DOES TAKE OFF.

THought experiment for doubters:
No idea if this has been mentioned before but imagine you are standing in a swimming pool, the floor starts moving backwards slowly, eventually you start going backwards as well. Now you start pulling yourself forward with your arms, pushing the water backwards, Pull yourself forward hard enough and you go forward, the only thing stopping you is the friction of the pool bottom on your feet.

To get from there to plane on the runway i will leave to you to finish off, it will help the realisation that way.

Thankyou

Yeehaw

26th May 2006 - 11:41 AM

QUOTE (joedawson+May 26 2006, 05:43 AM)

As Fallen says above, this is exactly where most people trip up with this argument - they forget that the planes forward propulsion is in no way linked to the surface it's traveling on.

Humans, cars, anything on a conveyor belt where there only means of forward propulsion is via contact with the belt surface, will remain stationary if the belt moves in the opposite direction.

A better analogy would be to say, if you were on a bicycle on a conveyor belt, and pulled on a rope attached to a stationary object in front of the conveyor belt - THEN would you move forward? of course you would, the belt can do whatever it wants, you are gaining forward momentum from something unconnected to the belt. Now let go of the rope and pedal........

Fynlcut

26th May 2006 - 01:21 PM

Wow got active in here again.

egnorant

26th May 2006 - 02:02 PM

QUOTE (joedawson+May 26 2006, 05:43 AM)

You are back to the different point of reference argument.
Many have tried to equate the force or effort as movement.
If I get on a plane in New York and fly to L.A. is there any doubt that I have "moved"? Even though my personal effort is almost nil.
Same as a man running on a treadmill is using a lot of effort in a quest to NOT move.

The "no fly" folks are saying that the effort (force) that the plane uses to keep from being moved backwards by the conveyor is movement.

This is actually just a balance of opposing forces.
A rock on a table is a balance.....gravity pulls down..table presses up.
No movement!
My favorite is the beach ball on the fan that just bobs up and down at the dept. store. Even my niece had to agree that the beach balls speed in any given direction averaged out to zero.

I am still wondering which of these new guys is actually ATL5P!
Bruce

Jack

26th May 2006 - 02:46 PM

QUOTE (Fallen+May 26 2006, 08:42 AM)

The original question has nothing to do with friction. The conveyor belt will match the [ground speed] of the WHEELS, no matter how or why they are moving at that speed. The original question DOES NOT STATE THAT THE PLANES WHEELS ARE WHAT IS MOVING THE CONVEYOR BELT.

Planes engines are off, conveyor belt is at 0.

Planes engines increase so that the plane (were it on a normal runway) would be moving 50mph, conveyor belt is at -50mph.

Planes engines increase so that the plane (were it on a normal runway) would be moving 100 mph, conveyor belt is at -100mph.

Keep going like this to infinity, the plane's relative motion is still ZERO, thus no lift, thus no takeoff.

krreagan

26th May 2006 - 03:21 PM

QUOTE (Jack+May 26 2006, 07:46 AM)

QUOTE (Fallen+May 26 2006, 08:42 AM)

Since when do you measure a planes speed at the wheels? never! (ground speed is not measured through the wheels) you measure a planes speed through the air!

Okay Jack, The plane is at full thrust! (tens of thousands of pounds of thrust) What force (or friction) is being applied to the plane to counter this thrust????? Remember wheels are designed to minimize friction! and we cannot forget about Mr. Newtons laws! action...reaction...
The answer is... there is none!, nada!, zip!, ziltch! so the plane moves forward and takes off!

This is simple physics people! clear away the clutter that does not matter! The only thing the belt does is make the wheels spin twice as fast as the planes ground speed.

Krreagan

sooks

26th May 2006 - 03:49 PM

Wow..certainlly did get active in here again... good to see krreagan is back on the horse.

Everythign relates to force. IF you think it cant take off.... tell me what force/s holds the plane from moving.

TAB68

26th May 2006 - 04:28 PM

All of you idiots that think this plane will take off need your a%# kicked. Morons! Do any of you have any idea what makes a f#%$ing plane fly? Look up "Bernoulli's principle" and stop commenting on engineering questions that you have no clue about. Dumb F-ers!

sooks

26th May 2006 - 04:43 PM

QUOTE (TAB68+May 26 2006, 04:28 PM)

hey dumbshit... think before you speak.. how old are you 15.

No one here is saying that the plane is taking off without the plane actually moving forward. Yes we know what bernoulis principal is.. and yes.. THE PLANE MOVES FORWARD THUS CREATING AIR OVER AND BENEATH THE WINGS THE SUFFICIENT PRESSURE DIFFERENCE CREATED BY THE SHAPE OF THE WING CREATES LIFT WHICH MAKES THE PLANE FLY..... assclown!!

how about you research the thread a little bit before making your own self look like a *****

Jack

26th May 2006 - 04:46 PM

QUOTE (krreagan+May 26 2006, 03:21 PM)

QUOTE (Jack+May 26 2006, 07:46 AM)

QUOTE (Fallen+May 26 2006, 08:42 AM)

Perfect question.

What is being applied to the plane to counter the thrust? THE TREADMILL. It does not counter the thrust itself, but the resultant action of the thrust...which is forward motion.

The conveyor belt counters the forward motion of the plane. Plane wants to go 100mph due to the thrust, the conveyor belt moves in the opposite direction 100mph.

Action-engine thrust
Reaction-plane moves and wheels roll along the runway.

But in this case - the runway starts moving backwards to match the forward motion of the plane.

Plane increases thrust. Conveyor belt moves faster. And so on.

How do you get a positive number out of 100mph + (-100mph)?

Don't make it too hard...that is the downfall of any good trick question.

TAB68

26th May 2006 - 05:17 PM

SOOK, you are a true idiot! If the plane is not moving with respect to the air around it ...it will not take off! It is as simple as that. FYI...I did read the complete thread and many people are way off base including your ignorant ***.
P.S. If you'd like to take this argument somewhere I'd be glad to show you how fast you can fly dickface.

dapascha

26th May 2006 - 05:49 PM

QUOTE (Jack+May 26 2006, 04:46 PM)

QUOTE (krreagan+May 26 2006, 03:21 PM)

QUOTE (Jack+May 26 2006, 07:46 AM)

QUOTE (Fallen+May 26 2006, 08:42 AM)

QUOTE

Action-engine thrust
Reaction-plane moves and wheels roll along the runway.

Well, there you've said it: the action is provided by the engine's thrust, the reaction is that (1) the plane moves and (2) the wheels roll along the runway. Not (1) the wheels's start rolling, and (2) the plane moves.

This means that the wheels are not directly involved in the planes thrust-issues. These are about engines displacing air, air that is not influenced by the treadmill. You could spin the wheels forwards or backwards, it doesn't matter much, since the force applied by the engines will always be far greater than the forces acting on the plane through the wheels (which are indeed designed to have as [I]little{/I] friction as possible.

The plane will take off.

krreagan

26th May 2006 - 06:08 PM

QUOTE (TAB68+May 26 2006, 09:28 AM)

Having taught physics! I think I know a little about the forces involved. This is a perfect example of the type of problem I would give to undergrads to see if they had the intuition to clear away all the irrelevant junk and get to the crux of the problem. The belt is truly irrelevant!

A plane flies by having air move over the wing to produce lift! the engines use the air (not the belt) to produce thrust (force)! the belt CANNOT impart enough force through a little friction, to stop the plane from accelerating! The problem states that the belt matches the "speed" of the pane! this is the forward velocity of the plane relative to the runway!. so if the plane is not moving forward, why is the belt moving? It's suppose to match the speed!

So if you are so enlightened in the principals of physics... tell us all where the forces are that keep the plane from accelerating down the runway! after all a 747 produces several hundred thousand pounds of thrust!

Krreagan

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