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#617350 - 29/12/06 04:15 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


ok i can't be bothered to read 19 pages of stuff, but for a plane to become airborne, you need to have air moving over the wings to create lift. so if the plane has zero ground speed (engines are only making the plane keep up with the conveyor), then it doesn't fly.

aerodynamics 101 wink

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#617351 - 29/12/06 04:33 PM Re: Know that if you do not post in this thread today the human race may cease to exist
MidnightX Offline
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Registered: 08/03/01
Posts: 3745
Loc: Jacksonville, Florida
Quote:
Originally posted by JayZ:
ok i can't be bothered to read 19 pages of stuff, but for a plane to become airborne, you need to have air moving over the wings to create lift. so if the plane has zero ground speed (engines are only making the plane keep up with the conveyor), then it doesn't fly.

aerodynamics 101 wink
I dunnoooooo..... people here beg to differ!!!!

Great, now this is gonna go another 10 pages.

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#617352 - 29/12/06 04:38 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


TJ, I hope this helps you. Listed below in reverse appearing order are our "Special" XOC members:

JayZ
Mobycat
far west x
RiNky
NY Madman
Paul H
Mostly_Harmless
MarGinJoey

This doesn't include those that thought the bullet that was dropped would hit the ground first... I didn't have the patience to track 2 things at once.

[Too much XOC]

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#617353 - 29/12/06 04:49 PM Re: Know that if you do not post in this thread today the human race may cease to exist
NY Madman Offline
Member
*

Registered: 09/05/02
Posts: 5232
Loc: Florida
Quote:
Originally posted by porsche996:
TJ, I hope this helps you. Listed below in reverse appearing order are our "Special" XOC members:

JayZ
Mobycat
far west x
RiNky
NY Madman
Paul H
Mostly_Harmless
MarGinJoey

This doesn't include those that thought the bullet that was dropped would hit the ground first... I didn't have the patience to track 2 things at once.

[Too much XOC]
You obviously haven't read the entire thread.

I am no longer dedicated to the position that it will not fly.

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#617354 - 29/12/06 05:07 PM Re: Know that if you do not post in this thread today the human race may cease to exist
MBFlyerfan Offline
Member

Registered: 30/04/01
Posts: 4450
Loc: NJ, Just east of the Walt.
It seems alot of people are stuck on the preconception that the wheels will be propelling the plane and therefore will just stand still on the treadmill.

Its been said 100 times already, but the engines do the propelling, thus negating any effect the treadmill would have.
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#617355 - 29/12/06 06:13 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 Rockaholic:
Here's another one to ponder

An airplane is on an infinately long Aircraft carrier. As this airplane attempts to take off in one direction, the aircraft carrier moves in the exact same speed in the opposite direction (so that the plane appears to be staying in the same spot to a impartial observer who is not on the aircraft carrier)....

Does the plane take off?
If the plane always appears to be in the same spot, then it's not moving through space, it's not moving through air, so it's not gonna take off. In order for the plane not to move through air, its means of propulsion must not be coming from the plane, it must come from the carrier (i.e. the infinitely long catapult).

This problem differs in that you specifically stated that the plane does not move absolutely, whereas the original scenario only mentions motion of the plane and the conveyor belt. Your plane may be in motion relative to the carrier, but in your scenario, the plane is not in motion relative to the air (or to the rest of the world).

So, again, no, your plane won't take off.
_________________________
4x4 in uppercase is $X$!!!
1997 R50: VG33E/RE4R01A/TX10/3.7/R200A/ARB/4.636/H233B/ARB/4.636/321150R15

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#617356 - 29/12/06 06:17 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:
I am no longer dedicated to the position that it will not fly.
You don't have to recant your original position:

Quote:
Originally posted by XPLORx4 (from page 11):
Based on Xorand's response, I believe it may be possible in the hypothetical scenario for the plane to not take off, so I am in agreement with NYMadman, but not because the engines don't actually move the aircraft further forward on the runway. Note: the hypothetical scenario is vague about the term "speed", and it does not provide any details about the physical environment. Most of us are filling in the blanks with what we perceive as "common knowledge" in order to arrive at our conclusion that the plane will take off.

Here's something that only Xorand hinted at (which would prevent the plane from taking off):

The conveyor is either moving at an infinite speed, if its speed-detection mechanism uses the plane's wheelspeed sensors, or it's moving opposite to the plane's groundspeed, if its mechanism is based on that. Now, we know that inifinity is a theoretical concept, and that wheel bearings and tires certainly cannot REALLY rotate at an infinite speed before self-destructing (which would then cause the conveyor to stop). So, without functional wheels, the plane can't overcome the friction of its broken landing gear sticking out beneath its belly, and it won't take off.

If the conveyor moves backwards at the same speed the plane moves forwards through space, then you would need to know the design limitations of the wheel bearings and tires to determine if they can spin at twice the take-off speed of the aircraft. If they can't handle it, again you have broken landing gear and the plane will likely careen out of control as it rolls down the runway at 180+mph. If the landing gear can handle those speeds, then the aircraft will indeed take off.
_________________________
4x4 in uppercase is $X$!!!
1997 R50: VG33E/RE4R01A/TX10/3.7/R200A/ARB/4.636/H233B/ARB/4.636/321150R15

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#617357 - 29/12/06 06:53 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Southernx7 Offline
Member

Registered: 24/03/03
Posts: 1252
Loc: Sunny Florida
If the Jaguars could get a few receivers and an accurate QB, we might be good next year.

Everybody sinnnnnnnggggg

The Jags still suck, the jags still suck.......

but damn can Jones-Drew run.
_________________________
Up The Irons!!

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#617358 - 29/12/06 08:21 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 Rockaholic:
Here's another one to ponder

An airplane is on an infinately long Aircraft carrier. As this airplane attempts to take off in one direction, the aircraft carrier moves in the exact same speed in the opposite direction (so that the plane appears to be staying in the same spot to a impartial observer who is not on the aircraft carrier)....

Does the plane take off?
Given calm winds, no. The plane does not take off. It will be at the same point relative to the air surrounding it, and thereby have attained a net of zero airspeed. However, the proposed scenario is even more unlikely than the conveyor the size of a runway. An aircraft carrier achieving speeds at which an aircraft could obtain lift would take such immense power as to be just about unthinkable. Besides which, the resulting movement of the flight deck would preclude a safe launch. But I'm just spitballin here.

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#617359 - 29/12/06 08:26 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


ok, i might as well chime in on the bullet gun thing too.

they both hit the ground at the same time. gravity affects them equally, but the one fired from the gun also has a forward motion component to it. i could get into vectors and all the scientific crap but i wont. wink

edit: here is a link explaining lift. note the final paragraph titled 'no motion, no lift'.

http://www.grc.nasa.gov/WWW/K-12/airplane/lift1.html

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#617360 - 29/12/06 08:40 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Mobycat Offline
Member
*****

Registered: 12/09/00
Posts: 8374
Loc: the hue of dungeons and the sc...
OK, from a pilot:

Quote:
You are correct. Think of it this way. The wings provide the lift. They need a rush of air to do that. Tell your 3rd graders to think of themselves sitting on the wing of an airliner taking off from a non-conveyor-belt runway. Imagine the 150 mph winds they would feel in their face, which the wings turn into lift.
but, sitting on wing of the conveyor-belt-runway plane, they wouldn't feel any wind at all. So, all you would be doing is wasting a lot of fuel and creating unnecessary carbon dioxide.

A more realistic situation is to take a Maule aircraft (attached). It will take off at 50mph. So, if you pointed it on the runway (or anywhere else!) into a 50mph headwind, it would take off straight above of its current position. Point it into a 55 mph wind, and it will take off, and fly 5mph (relative to the ground) backwards!!
_________________________
"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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#617361 - 29/12/06 08:47 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Mobycat Offline
Member
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Registered: 12/09/00
Posts: 8374
Loc: the hue of dungeons and the sc...
Quote:
Originally posted by MattyX:
The plane does not take off. It will be at the same point relative to the air surrounding it, and thereby have attained a net of zero airspeed.
DING DING DING!!!

That's the EXACT same scenario as the conveyor belt!
_________________________
"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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#617362 - 29/12/06 08:49 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Just because it's coming from a pilot, doesn't mean it's right. I'm an air traffic controller, I tell pilots what to do all day, but that doesn't mean a damn. Go ahead and try the balsa-plane-with-a-rubber-band-powered-prop trick on the treadmill at your local gym. See if it works, then try to figure it out.

Of course, it's been done.
Quote:
It was an interesting argument, but as things progressed, more rational heads prevailed, pointing out that the airplanes do not apply their thrust via their wheels, so the conveyor belt is irrelevant to whether the airplane will takeoff. One guy even got one of those rubber band powered wood and plastic airplane that sell for about a buck, put it on the treadmill someone foolishly donated to the Lounge years ago, thinking that pilots might actually exercise. He wound up the rubber band, set the treadmill to be level, and at its highest speed. Then he simultaneously set the airplane on the treadmill and let the prop start to turn. It took off without moving the slightest bit backwards.
You've read the whole thread, right?

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#617363 - 29/12/06 08:51 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Mobycat Offline
Member
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Registered: 12/09/00
Posts: 8374
Loc: the hue of dungeons and the sc...
Quote:
Originally posted by MattyX:
Just because it's coming from a pilot, doesn't mean it's right. I'm an air traffic controller, I tell pilots what to do all day, but that doesn't mean a damn. Go ahead and try the balsa-plane-with-a-rubber-band-powered-prop trick on the treadmill at your local gym. See if it works, then try to figure it out.

Of course, it's been done.
Quote:
It was an interesting argument, but as things progressed, more rational heads prevailed, pointing out that the airplanes do not apply their thrust via their wheels, so the conveyor belt is irrelevant to whether the airplane will takeoff. One guy even got one of those rubber band powered wood and plastic airplane that sell for about a buck, put it on the treadmill someone foolishly donated to the Lounge years ago, thinking that pilots might actually exercise. He wound up the rubber band, set the treadmill to be level, and at its highest speed. Then he simultaneously set the airplane on the treadmill and let the prop start to turn. It took off without moving the slightest bit backwards.
You've read the whole thread, right?
That rubber band plane has almost no weight. It's wheels obviously moved faster than the treadmill.

If the jet is weightless, all bets are off...then yes, it could take off.
_________________________
"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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#617364 - 29/12/06 08:58 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 Mobycat:
Quote:
Originally posted by MattyX:
[b]The plane does not take off. It will be at the same point relative to the air surrounding it, and thereby have attained a net of zero airspeed.
DING DING DING!!!

That's the EXACT same scenario as the conveyor belt![/b]
BZZZZZZ! Sorry, you are incorrect. The scenario is not the same. Examine, if you will, scenario #1:
Quote:
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?
Nothing in this scenario says that the plane must remain stationary. In fact, it states with certainty that the plane must move (otherwise no speed at all. Now for scenario #2:
Quote:
An airplane is on an infinately long Aircraft carrier. As this airplane attempts to take off in one direction, the aircraft carrier moves in the exact same speed in the opposite direction (so that the plane appears to be staying in the same spot to a impartial observer who is not on the aircraft carrier)....

Does the plane take off?
Given the stipulation that the aircraft remains in the same point in space (as was described in the parenthesis in the above quote), no airspeed at all could be generated, except what was necessary to counterract the minimal friction of the flight deck under the wheels. If the carrier and plane were free to move to any point in space, yet the only stipulation being that their speed must be equal in opposite directions, the aircraft would still take off.

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#617365 - 29/12/06 09:03 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 Mobycat:

If the jet is weightless, all bets are off...then yes, it could take off.
We have weightless aircraft. Blimps and hot-air balloons. But they're not relevant to this discussion.

So the balsa plane takes off because it's light. Get a bigger balsa plane, and try it again. then try it again with a larger, heavier RC plane. Then with an even larger one. If the plane's propulsion system can push enough AIR to move its own weight fast enough to achieve lift, is certainly will not sit still because something's turning its wheels.

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#617366 - 29/12/06 09:17 PM Re: Know that if you do not post in this thread today the human race may cease to exist
socalpunx Offline
Member

Registered: 24/08/01
Posts: 6327
Loc: The land of losers and liberal...
There is nothing that can get me to go back and read the whole thread but I would love to throw my hat into the ring:

Why is a Harrier jet able to take off from what is basically a stable position while hovering? The plane achieves flight through propultion rather than wind speed and there is no need for a runway or wheels for that matter.

I have to throw my lot in with the "it flys" crowd since a plane achieves flight through propultion at a certain level regardless of the land speed.

But I still wonder: why does it take X hundreds of feet for a plane to take off when all a pilot could do is set the throttle wide open and slingshopt the plane.

So who the hell knows....
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If we do not succeed, then we run the risk of failure. - Vice President James Danforth "Dan" Quayle

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#617367 - 29/12/06 09:25 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Welcome, SCPX. To your question-

what you've described is done frequently. The thing is, it must gain momentum to achieve airspeed. Airspeed is not created by sitting still and pushing air, you must travel through air to have airspeed.

So while a plane spools up with the brakes on, it's like a boat at 3/4ths throttle tied to a pier. Get free of the line, and it's off like a shot. If the boat is a hydrafoil, it will still need to gain momentum and speed through the water to be raised up on it's foils. Do I make any sense, ever?

::ETA:: While the engine is turning, air flows only through the turbine/prop path/both. In order to achieve lift, you must create airflow over the entire wing. This is why forward motion is required.

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#617368 - 29/12/06 09:28 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


20 pages and still in the club house? come on, lets take this to the ALR.

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#617369 - 29/12/06 09:37 PM 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
Quote:
Originally posted by zuzuman03:
20 pages and still in the club house? come on, lets take this to the ALR.
Fuck you queer
_________________________
Sharam can have my sister

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#617370 - 29/12/06 09:58 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


[Spit]

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#617371 - 29/12/06 10:27 PM Re: Know that if you do not post in this thread today the human race may cease to exist
NY Madman Offline
Member
*

Registered: 09/05/02
Posts: 5232
Loc: Florida
Quote:
Originally posted by MattyX:

Go ahead and try the balsa-plane-with-a-rubber-band-powered-prop trick on the treadmill at your local gym. See if it works, then try to figure it out.
Matt ...

The rubber band powered balsa wood plane experiment is not a good test of the scenario that is being discussed in this thread. No where near a good test. I think you know that.

I also have a question for you....

You seem to think the plane on the aircraft carrier would not take off and you are using virtually the same argument that people are using against the plane on the conveyor belt. Why is that?

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#617372 - 29/12/06 10:38 PM 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
Quote:
Originally posted by JayZ:
edit: here is a link explaining lift. note the final paragraph titled 'no motion, no lift'.

http://www.grc.nasa.gov/WWW/K-12/airplane/lift1.html
Maybe you should have read the paragraph and not just the title
Quote:
Lift is generated by the difference in velocity between the solid object and the fluid. There must be motion between the object and the fluid: no motion, no lift. It makes no difference whether the object moves through a static fluid, or the fluid moves past a static solid object.
One problem is that people are assuming that ground speed and air speed are one and the same, when in fact they are not.

Take my Kites, for example, which fly based on the same principles as an airplane - only they have no groundspeed...which means they rely on the air moving past the kite to generate lift.

Again, it makes no difference whether the object moves through a static fluid, or the fluid moves past a static solid object. In either case, lift is acheived.

Taht's the other problem, people are assuming that lift only occurs if the plane is moving in relation to the ground, as they assume the ground and air move together - which is compltely false.

If I run 5 mph towards the east on a calm, windless day, I will feel a 5 mph breeze coming from the west - the difference between my velocity (5mph east) and the airs velocity (omph).
That is my groundspeed is 5mph, my windspeed is 5mph.

If I run 5mph towards the east with a tailwind at 5mph, I will feel no wind - because now there is no difference between my velocity (5mph east) and the airs velocity (5 mph east)
that is my groundspeed is 5mph, but my windspeed is 0mph.

This is important, because as the NASA link states in the "no motion, no lift" paragraph
Quote:
Lift is generated by the difference in velocity between the solid object and the fluid.
Taking the conveyor belt -
Remember you have to use vector addition, and everything has to equal out.
If the plane is moving at 100mph, the Belt is also moving at 100mph in the opposite direction (add them together, you get 0 mph)
A person (impartial observer) standing off of the belt sees the plane staying in a stationary spot, and feels no windspeed (0mph). They see a person on the belt moving with the belt (away from the plane) at a speed of 100mph.

The person on the belt sees the plane moving away at a rate of 200mph (the combined speeds of the person and plane), and feels a windspeed of 100mph (the difference between speed the person is travelling on the belt and the speed of the air (omph) felt by the observer). The person on the belt sees the observer moving away from them at a rate of 100 mph.
The plane sees the person on the belt moving away at 200mph. The plane sees the observer as not moving in relation to it. The Plane also feels a windspeed of 100mph.

Now the vector addition -
The plane is moving at 100mph in one direction, the belt/person at 100mph in the opposite direction - they cancel each other out (0mph total movement)
The observer and the person on the belt see each other moving away at 100 mph (in opposite directions) so that cancels each other out. (0 mph)
The person on the belt and the airplane see each other moving away at 200 mph in opposite directions, so that cancels each other out. (0mph)
The airplane and the observer do not see any change in distance between them - they cancel out (0mph)
The person on the belt feels a windspeed of 100mph (because they are moving in relation to the wind at 100mph)- since the observer feels no windspeed, the airplane must cancel the person on the belts windspeed of 100mph out by feeling a windspeed of 100mph in the opposite direction (which would be going from head to tail on the plane).
_________________________
Jeffrey
I'm just trying to put my tires on the rocks of life.

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#617373 - 29/12/06 10:44 PM 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
Oh, ands to those who think that groundspeed and airspeed are one and the same....

When the air moves (wind), does the ground move with the air?
_________________________
Jeffrey
I'm just trying to put my tires on the rocks of life.

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#617374 - 29/12/06 11:27 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Quote:
Originally posted by NY Madman:
Quote:
Originally posted by MattyX:

[b]Go ahead and try the balsa-plane-with-a-rubber-band-powered-prop trick on the treadmill at your local gym. See if it works, then try to figure it out.
Matt ...

The rubber band powered balsa wood plane experiment is not a good test of the scenario that is being discussed in this thread. No where near a good test. I think you know that.

::ETA:: Rockaholic- I'll get to your stuff tomorrow. I'm tired.

I also have a question for you....

You seem to think the plane on the aircraft carrier would not take off and you are using virtually the same argument that people are using against the plane on the conveyor belt. Why is that?[/b]
Explain to me, madman, why the balsa plane experiment is not a "good test."

There is a stipulation in the carrier scenario that the plane remain in the same point in space. There is no such stipulation in the conveyor scenario. In the conveyor scenario, the aircraft can move, regardless of what the surface does.

Once again, in the Carrier scenario, ROck stipulated that the aircraft must stay in the same position relative to the earth and the air. Of course, if you remove this stipulation, and replace the conveyor with an "infinitely ling aircraft carrier", the answers are exactly the same. The problem with Rock's question is that there's no way the motion of the aircraft carrier could affect a plane that's trying to fly off it, other than steaming downwind.

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