Riddle Me This......... - Page 3

Dave_au · 30-11-2005, 01:26 PM

Quote:

Originally Posted by Malakai

The plane is not stationary!!! You apply thrust and the plane moves!!! Because the engines pull the plane through the air. They do NOT push against the ground.

Its stationary relative to the atmosphere and ground.

All these theorys are great and all, but for the flight principle to work, the air must travel at the same speed as the conveyorbelt.

Steffo · 30-11-2005, 01:29 PM

Anyone with a good rc plane and a treadmill should be able to test this theory.. so, anyone on AFF got those two things? The results would be most interesting...

**Charliewool** · 30-11-2005, 01:33 PM

Quote:

Originally Posted by Steffo

Anyone with a good rc plane and a treadmill should be able to test this theory.. so, anyone on AFF got those two things? The results would be most interesting...

Zetec has both by the look of it...

SB076 · 30-11-2005, 01:41 PM

Quote:

Originally Posted by v8capri

The plane will not take off
the air speed going over the wings is what creates the lift.
the jets only provide the thrust to get it moving to pass the air over the wings,
so yes the plane will be stationary, as the jets propell it forward yet the treadmaill pulls it back, there will be no 100 mph + air speed going over the wings to provide lift.

Cool thread

in real life it would be tricky to demo, but in theory it works well.

And the photo of the plane on the treadmill !! excellent !!

Agreed thats the why planes have wings and thats what provides the lift, engines provide thrust, which propels the plane forward however without significant air speed over the wings they are useless and the plane will stay on the ground

EA2BA · 30-11-2005, 01:42 PM

A plane needs air movement accross the wings, and the flaps will provide different rate of airflow accross the wings and produce lift, so zero air accross the wings would mean no lift can be produced, so no take off.

JAJH · 30-11-2005, 01:55 PM

My answer is it will DEFINITELY not take off. Here's another analogy... a glider has no form of thrust, it is towed by another plane or pulled by a winch. The only thing that gets a glider of the ground is what???? air flow over the wings, nothing to do with thrust. The answer is simple guys, you can have as much thrust as you like, but no air flow, no lift.

big_pete · 30-11-2005, 01:56 PM

Quote:

Originally Posted by JAJH

My answer is it will DEFINITELY not take off. Here's another analogy... a glider has no form of thrust, it is towed by another plane or pulled by a winch. The only thing that gets a glider of the ground is what???? air flow over the wings, nothing to do with thrust. The answer is simple guys, you can have as much thrust as you like, but no air flow, no lift.

but if the thrust is moving the plane forward, why is there no airflow?

Casper · 30-11-2005, 01:59 PM

Quote:

Originally Posted by Dave_au

Its stationary relative to the atmosphere and ground.

All these theorys are great and all, but for the flight principle to work, the air must travel at the same speed as the conveyorbelt.

thats the thing, its not stationary to the ground.

Think of it as a sea plane sitting on a fast flowing stream. Regardless how fast the water is running the plane will move forward almost immediatly because the prop is pushing against the atmosphere, the speed of the water is almost irrelevant. The plane will take of because the conveyer is moving but the atmosphere isnt.

SB076 · 30-11-2005, 02:00 PM

Quote:

Originally Posted by SB076

Agreed thats the why planes have wings and thats what provides the lift, engines provide thrust, which propels the plane forward however without significant air speed over the wings they are useless and the plane will stay on the ground

The plane will take off however as the conveyor can not counteract thrust (the engines thrust pulls the plane through the air) therefore the conveyor cannot hold the plane stationery and it will take off or run out of conveyor, but either way the plane will move forward.

EA2BA · 30-11-2005, 02:04 PM

Quote:

Originally Posted by SB076

The plane will take off however as the conveyor can not counteract thrust (the engines thrust pulls the plane through the air) therefore the conveyor cannot hold the plane stationery and it will take off or run out of conveyor, but either way the plane will move forward.

It says the conveyor will match the plane speed 100% the same in the opposite direction !

SB076 · 30-11-2005, 02:05 PM

Quote:

Originally Posted by JAJH

My answer is it will DEFINITELY not take off. Here's another analogy... a glider has no form of thrust, it is towed by another plane or pulled by a winch. The only thing that gets a glider of the ground is what???? air flow over the wings, nothing to do with thrust. The answer is simple guys, you can have as much thrust as you like, but no air flow, no lift.

thats what I originally thought, but the engines thrust does not act against the conveyor, it pulls the plane through the air, meaning regardless of how fast the conveyor goes, cause it only acts on free spinning wheels the plane must move forward which will create air flow and lift, the only difference is that the wheels will spin much quicker than normal.

Casper · 30-11-2005, 02:05 PM

Quote:

Originally Posted by EA2BA

It says the conveyor will match the plane speed 100% the same in the opposite direction !

it cant though.. its against the laws of physics

SB076 · 30-11-2005, 02:06 PM

Quote:

Originally Posted by EA2BA

It says the conveyor will match the plane speed 100% the same in the opposite direction !

Yes but it cant, the conveyor is acting on free spinning wheels the engines act against the stationery air and will pull the plane forward

Perana · 30-11-2005, 02:07 PM

Once again... the conveyor moving the wheels backwards will not effect the forward motion of the plane since the motion is caused NOT by the wheels but by Jet/Prop engines. Wheels are only on a plane to reduce friction when landing/taking off..

JAJH · 30-11-2005, 02:08 PM

Quote:

Originally Posted by big_pete

but if the thrust is moving the plane forward, why is there no airflow?

But as I said, thrust is only to propel the plane forward, then as a result of that forward motion does it create airflow over the wings. If the plane is in effect 'stationary', how can lift be created? If this theory were correct that it WILL takeoff, why do we use long runways around the world and use so much valuable land. The eggheads would build runways 100feet long with super powered conveyor belts.

Perana · 30-11-2005, 02:09 PM

How is the plane stationary though... there is a Force Forward from the Engines and much smaller force backwards from the friction in the wheels... So the plane will move forward... its Yr 10 physics...

Sourbastard · 30-11-2005, 02:12 PM

Who cares as long as the stewardess has ample cleavage, the beer is cold and plentiful, and they keep me placated with peanuts and chips in little bags!

Whats the next thread gonna be about? What shade of blue the sky is?

EA2BA · 30-11-2005, 02:13 PM

Quote:

Originally Posted by Casper

it cant though.. its against the laws of physics

since when has this thread been reality based

_2:

:

Casper · 30-11-2005, 02:14 PM

Quote:

Originally Posted by JAJH

But as I said, thrust is only to propel the plane forward, then as a result of that forward motion does it create airflow over the wings. If the plane is in effect 'stationary', how can lift be created? If this theory were correct that it WILL takeoff, why do we use long runways around the world and use so much valuable land. The eggheads would build runways 100feet long with super powered conveyor belts.

The plane will still need the same length runway. In simple terms.. the conveyor can be going in any direction, at any speed, doing anything it likes, it wont make any difference. All the wheels are doing is keeping the thing off the ground and allowing it to move.

In the opposite, say the conveyor moves the same direction as the plane. It will still move forward at the same speed as it does on a stationary runway.. the only difference is the wheels wil actually never rotate. It will still take off in the same length of runway as it normally does.

Perana · 30-11-2005, 02:15 PM

Quote:

Originally Posted by sourbastard

Who cares as long as the stewardess has ample cleavage, the beer is cold and plentiful, and they keep me placated with peanuts and chips in little bags!

Whats the next thread gonna be about? What shade of blue the sky is?

Here, Here !

JAJH · 30-11-2005, 02:19 PM

Quote:

Originally Posted by Casper

The plane will still need the same length runway. In simple terms.. the conveyor can be going in any direction, at any speed, doing anything it likes, it wont make any difference. All the wheels are doing is keeping the thing off the ground and allowing it to move.

In the opposite, say the conveyor moves the same direction as the plane. It will still move forward at the same speed as it does on a stationary runway.. the only difference is the wheels wil actually never rotate. It will still take off in the same length of runway as it normally does.

Shane, we are not talking about whether it will move or not, we are asking the question if it will fly? The simple logic is - the plane is relative to the ground and stationary, not moving one inch in either diection. If it has no airspeed and no air flow over the wings, how can it create lift and fly?

Sourbastard · 30-11-2005, 02:24 PM

Quote:

Originally Posted by JAJH

how can it create lift and fly?

Through the Magic of David EFFING Copperfield....

Mr. CVE · 30-11-2005, 02:28 PM

Yes but the converyer is moving the plane backwards, so the thrust must move it forwards.so while the plane's road speed through the wheels the plane air speed will be zero

Casper · 30-11-2005, 02:28 PM

Quote:

Originally Posted by JAJH

Shane, we are not talking about whether it will move or not, we are asking the question if it will fly? The simple logic is - the plane is relative to the ground and stationary, not moving one inch in either diection. If it has no airspeed and no air flow over the wings, how can it create lift and fly?

It will move. It will move in relation to the "earth" ground speed, the conveyor is of no relevance at all. As I said, the convayor can move forward, backwards, any speed it likes. The plane will still travel in a forward direction relative to its current position on the planet (its GPS position will actually change), it will create airflow over the wings from this forward movement and it will take off.

DivHunter · 30-11-2005, 02:30 PM

Quote:

Originally Posted by big_pete

ok, ive seen this on a couple of forums now, and i dont think a conclusion has been reached for this little problem........

Quote:

A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer 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 what do you think????

That quote should be taken out and shot.

Perana · 30-11-2005, 02:31 PM

Although friction in the wheel bearings and rolling resistance will effect forward motion slightly there will be no where enough to adversely effect it.

The only way that the conveyor will have a major effect on the plane is if the brakes are on...

JAJH · 30-11-2005, 02:33 PM

Quote:

Originally Posted by Casper

It will move. It will move in relation to the "earth" ground speed, the conveyor is of no relevance at all. As I said, the convayor can move forward, backwards, any speed it likes. The plane will still travel in a forward direction relative to its current position on the planet (its GPS position will actually change), it will create airflow over the wings from this forward movement and it will take off.

There is NO forward movement - NO airflow.

SB076 · 30-11-2005, 02:34 PM

Quote:

Originally Posted by v8capri

Yes but the converyer is moving the plane backwards, so the thrust must move it forwards.so while the plane's road speed through the wheels the plane air speed will be zero

No as the conveyer will move the plane back initially due to friction, but as the wheels are freespinning the conveyor cannot move the plane back and the engines will pull the plane through the air and forward regardless of what the conveyor is doing therefore the conveyor really is irrelevant. The plane will move forward and will take off as normal. The planes air speed will not be zero.

Mr. CVE · 30-11-2005, 02:35 PM

Quote:

Originally Posted by Perana XR8

Although friction in the wheel bearings and rolling resistance will effect forward motion slightly there will be no where enough to adversely effect it.

The only way that the conveyor will have a major effect on the plane is if the brakes are on...

hrmm,i think you have a point,
I take it all back now,
The tyres may explode as they will exceed their speed rating .
but you may be right.

the wheels will be turning quite fast.

Turns out I am the

Mark351 · 30-11-2005, 02:37 PM

Part of the answer lies in the original question.

Sure, the conveyor belt 'matches' the plane's speed (ignore reality Casper, this is hypothetical, and in the end, it's irrelevant anyway...), but if the plane is happily doing take-off speed (relative to the ground, because there's no wind) then it just means the conveyor belt is doing the same speed in the opposite direction.

The plane's thrust provides accelaration that equates to a gain in speed, but the conveyor belt would be constantly increasing in speed itself to compensate, but never quite matching it - allowing the plane to eventually reach a take-off speed.