Riddle Me This......... - Page 4

Perana · 30-11-2005, 01:37 PM

Yes thats assuming that the tyres/wheel bearings can take the load/heat !

DivHunter · 30-11-2005, 01:38 PM

Quote:

Originally Posted by JAJH

There is NO forward movement - NO airflow.

It will move forward because the wheels can spin as fast as they like it is not relying on their traction to move forward only the thrust of the engines. If it was a car then yeah it won't move but this is a plane. How do you think it stays up once it's in the air? It doesn't say 'will it take off exactly where it is' does it?

But who the hell has a conveyer belt as a runway, that's one of the top ten dumbest things I have ever heard.

Seeing as we aren't specifying the type of plane it's a harrier jet, it takes off vertically so ner.

Casper · 30-11-2005, 01:38 PM

Quote:

Originally Posted by JAJH

There is NO forward movement - NO airflow.

Thats the thing, there is forward movement. The conveyor can do anything it likes it will not stop the aircraft from pushing the atmosphere back and creating enough force to move it forward. the wheels can move forwards, backwards, whatever it likes, it is driven by forcing the atmosphere back to create thrust... thefore making movement... therefore creating airflow over the wings and lift.
The wheels are freewheeling and have no bearing on the forward movement of the plane. Therefore the surface (and what it is doing) that the wheels are sitting on also cannot have any bearing on the planes movement.

Mr. CVE · 30-11-2005, 01:38 PM

Phew !!
this is solved, I can now get on with the rest of my life !!

Sourbastard · 30-11-2005, 01:39 PM

maybe replace the wheels with teapots.

DivHunter · 30-11-2005, 01:41 PM

Quote:

Originally Posted by sourbastard

maybe replace the wheels with teapots.

The harrier would still take off, just in more shiny teapot bling style.

Mark351 · 30-11-2005, 01:42 PM

In such a hypothetical scenario, we assume the plane has magic wheels/tyres that don't explode, such as we assume such a conveyor belt could actually be made and installed.

EA2BA · 30-11-2005, 01:43 PM

Its states tracks plane speed, so are thinking of wheels in the wrong train of thought here people

SB076 · 30-11-2005, 01:53 PM

Quote:

Originally Posted by Casper

Thats the thing, there is forward movement. The conveyor can do anything it likes it will not stop the aircraft from pushing the atmosphere back and creating enough force to move it forward. the wheels can move forwards, backwards, whatever it likes, it is driven by forcing the atmosphere back to create thrust... thefore making movement... therefore creating airflow over the wings and lift.
The wheels are freewheeling and have no bearing on the forward movement of the plane. Therefore the surface (and what it is doing) that the wheels are sitting on also cannot have any bearing on the planes movement.

I agree.

Just had an arguement with my brother about this we have decided to settle it by throwing two sea monkeys into a tank and having them fight to the death

JAJH · 30-11-2005, 02:01 PM

Quote:

Originally Posted by Fairmont99

It will move forward because the wheels can spin as fast as they like it is not relying on their traction to move forward only the thrust of the engines. If it was a car then yeah it won't move but this is a plane. How do you think it stays up once it's in the air? It doesn't say 'will it take off exactly where it is' does it?

But who the hell has a conveyer belt as a runway, that's one of the top ten dumbest things I have ever heard.

Seeing as we aren't specifying the type of plane it's a harrier jet, it takes off vertically so ner.

Read the question Dopey, it's a hypothetical? I never said anyone actually had a conveyor bely runway.

pb02 · 30-11-2005, 02:20 PM

Could God microwave a burrito so hot, that he himself could not eat it?

Dave_au · 30-11-2005, 02:20 PM

Quote:

Originally Posted by Casper

Thats the thing, there is forward movement. The conveyor can do anything it likes it will not stop the aircraft from pushing the atmosphere back and creating enough force to move it forward. the wheels can move forwards, backwards, whatever it likes, it is driven by forcing the atmosphere back to create thrust... thefore making movement... therefore creating airflow over the wings and lift.

Nope, lift is generated by a flow of air over the wings. The engines would be working at full power, moving the plane forward at a speed relative to take off/whatever speed you want on the conveyor belt.

The engines would suck air in, and thrust the air as hot gasses behind the plane. The thrust back from the engine does not cause air to flow over the wings, rather all it will do is suck air in like a vacuum cleaner, and expell the exhaust as one massive, relatively narrow channel of thrust.

How do the engines on the 717 provide lift to the wings?

Answer? They don't. Jet engines like this provide thrust, with relatively minimal pulling power/sucking power. The plane is pushed along by the thrust of the engines. Its the movement of the wing though a body of air that gives rise to lift.

Perana · 30-11-2005, 02:26 PM

Yes but the effect of moving the aircraft forward (which WILL happen in relation to the earth) created airflow over the wings therefore creating lift

Casper · 30-11-2005, 02:27 PM

Quote:

Originally Posted by Dave_au

Nope, lift is generated by a flow of air over the wings. The engines would be working at full power, moving the plane forward at a speed relative to take off/whatever speed you want on the conveyor belt.

The engines would suck air in, and thrust the air as hot gasses behind the plane. The thrust back from the engine does not cause air to flow over the wings, rather all it will do is suck air in like a vacuum cleaner, and expell the exhaust as one massive, relatively narrow channel of thrust.

Exactly.. It creates thrust. That thrust is against the atmosphere, not the ground. Therefore the thrust will move the plane forward (GPS forward..REAL forward) irrespective of what the conveyor is doing. So long as the conveyor does not change the surrounding atmosphere.. as it doesnt.. it can do what it likes, the plane will move forward through the atmosphere.. creating lift... and take off. The movement of the converyor cannot stop this, it has no effect on the plane whatsoever regardless of its speed or direction. Planes move forward based on thrust in the atmosphere not thrust driven through the ground. The wheels on a plane are simply there to hold the prop (or jet) off the ground and reduce friction. Replace the wheels with a cusion of air (hovercraft) and tell me that the conveyor will make any difference? It wont.. cause the thrust is irrespective of the ground. In this case the wheels or air cusion do the same job.. keeping the planes props off the ground.

Sourbastard · 30-11-2005, 02:27 PM

Quote:

Originally Posted by pb02

Could God microwave a burrito so hot, that he himself could not eat it?

God doesnt use microwaves. He uses a BBQ. Everyone knows that.

Dave_au · 30-11-2005, 02:27 PM

Quote:

Originally Posted by Perana XR8

Yes but the effect of moving the aircraft forward (which WILL happen in relation to the earth) created airflow over the wings therefore creating lift

But the plane is stationary on the conveyor belt as the conveyor belt is equalling the forward movement of the plane? thats my understanding.

Perana · 30-11-2005, 02:29 PM

Yes but because the wheels are relatively frictionless they will turn without providing much resistance to forward motion... In effect they would be just supporting the plane

TheSneakiness · 30-11-2005, 02:32 PM

I agree with this quote right here...

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!

Dave_au · 30-11-2005, 02:48 PM

Okay, to confirm my understanding of the case presented by Casper:

The plane requires to reach 200km/h to take off.
The plane moves forward against the conveyor belt
The plane moves at 150km/h conveyor belt speed
The conveyor belt moves 150km/h against the plane
The plane moves up the conveyor belt, as the wheels spin freely, absorbing the speed of the conveyor belt.
The plane takes flight at 200km/h - the wheels are spinning at 400km/h as the plane takes off.

THORNSPAWN · 30-11-2005, 02:48 PM

If there was a plane on the conveyor while the conveyor was moving and two people
standing either side of the conveyor held the wings and pushed the plane forward would
it move in relation to the ground?

Of course it would and how is this any different from the engine pushing the plane
forward relative to the surrounding environment?

Casper · 30-11-2005, 02:53 PM

Quote:

Originally Posted by Dave_au

Okay, to confirm my understanding of the case presented by Casper:

The plane requires to reach 200km/h to take off.
The plane moves forward against the conveyor belt
The plane moves at 150km/h conveyor belt speed
The conveyor belt moves 150km/h against the plane
The plane moves up the conveyor belt, as the wheels spin freely, absorbing the speed of the conveyor belt.
The plane takes flight at 200km/h - the wheels are spinning at 400km/h as the plane takes off.

The plane moves up the conveyor belt, as the wheels spin freely, absorbing the speed of the conveyor belt. This is it exactly. The wheels absorb the movement of the conveyor as they are freespinning. The speed of the wheels can be anything from 0 to 200,000,000MPH or more, it has no effect on the speed of the actual aircraft in the atmosphere.

So yes, that is correct.

EA2BA · 30-11-2005, 02:59 PM

it tracks plane speed, so if the plane moved forward at all it would have speed, if it had speed it would increase belt speed, hence plane has no speed, so no air over wings, so no lift, no flight. It would just mean that the belt could end up going faster then light speed to stop the plane moving, but it would not fly.

**Charliewool** · 30-11-2005, 03:02 PM

I have an idea:
Let's all take a hammer and nail and belt it through our right (or left) foot into a wooden floor and have a race. It will be far less painful and we will spend less time going in circles.

Casper · 30-11-2005, 03:09 PM

Quote:

Originally Posted by EA2BA

it tracks plane speed, so if the plane moved forward at all it would have speed, if it had speed it would increase belt speed, hence plane has no speed, so no air over wings, so no lift, no flight. It would just mean that the belt could end up going faster then light speed to stop the plane moving, but it would not fly.

Close.. The belt would certainly track the planes speed and react to it.. but I cant stop it by moving backwards (or forwards.. or stopped). The conveyors movement can do what it likes.. it cant stop the plane. Just replace "wheels" with "air cusion"... then you will see the conveyor has a zero effect on the planes movement.

**Charliewool** · 30-11-2005, 03:10 PM

Quote:

Originally Posted by flappist

This is a silly as "If I had I time machine could I kill my father when he was a child?"

So, What's the answer?.. could you??

:

EA2BA · 30-11-2005, 03:11 PM

This sounds like a job for MYTH BUSTERS

DOC · 30-11-2005, 03:16 PM

I have just listed this on the mythbusters notice board and will await thier reply. ( not showing just yet )

the site can be found at
http://www20.sbs.com.au/mythbusters/index.php?a=gb#

my money says it wont fly

We are currently debating this issue to no resolve, we would appreciate your valued input.
Regards
Doc

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?

42.57lb · 30-11-2005, 03:34 PM

OK, this one has come straight from the pen of a physicist (spelling??!?!?!) not myself, but one I know.

The plane will NOT take off because the lift that is required comes from air flowing over and under the wind surfaces. If it's a jet the push from the engines is what causes the wings to move through the air and 'generate' lift.

If it's a case of as soon as the wheels of the plane begins rolling the force against the runway will be zero, so resultant force on the plane is zero and there will be no net 'forward' movement... If the wings do not move forward then the lift effect is not possible.

If it's a prop plane (with huge props) it may be possible that the draught that the props produce from in front of the wing, may (unlikely!) be able to generate enough lift to take the plane off the runway. If this happens then the only force that would be present is the thrust and the plane will move forward and 'take off'

there you have it.

**Charliewool** · 30-11-2005, 03:39 PM

Well 42.57lb.... Your physicist needs to go back to school & re-investigate the interaction of matter and energy... Cause he's W R O N G!...

DOC · 30-11-2005, 03:42 PM

Quote:

Originally Posted by charliewool

Well 42.57lb.... Your physicist needs to go back to school & re-investigate the interaction of matter and energy... Cause he's W R O N G!...

Charliewool, you cant just say hes wrong, you need back that statement up with some facts.