A plane on a conveyor belt

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Clinkz said:
I havnt read the whole thread. In short, this whole thing is total rubbish because the question given is COMPLETELY different to the question answered.

The answer to the question 'will it take off' is NO. No upwards thrust is created as there is no air movement over the wings.

The answer to the question 'If the conveyor moves in the opposite direction at the same speed as the plane, can the plane ever over come the backwards force to provide enough thrust to move fowards and take off as normal' is YES. Once friction is overcome, the plane requires no more thrust to remain stationary on the conveyor and is able to accelerate forwards.

I will reiterate though, whoever first proposed 'will it take off' is a total retard.
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The question is...

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 the opposite direction). Can the plane take off?
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The answer is yes. Unless you want to be pedantic and say the movement doesn't specify take off speed.

Capn' $qu!ff said:
I say we build a Conveyer big enough and test the theory ourselves!
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Already been done and proven, see the Mythbusters Youtube links in this thread.
 
SpeedFreak said:
The problem that a lot of people have with this is the issue of friction. Scuzi has made it reasonably clear with the bike on the treadmill example, people are equating running on a treadmill to freewheeling on one.

If we take a wheel as a frictionless contact point, which is simplifying the issue slightly, but not overly, any object with a frictionless wheel when on a conveyor belt will remain unmoved by the speed of that conveyor belt.

Let's make this clear, the speed of the conveyor belt has zero effect on the forward or backward motion of this object because it's own frictionless wheel spins in the opposite direction to compensate for the motion of the conveyor.

If we then apply thrust from the engine of the aircraft, we can apply newtonian physics, and look at conservation of momentum with impulse effects. Basically, the mass of air shooting really fast out the back causes the plane to begin to move forward. If it can move forward it can achieve lift and therefore take off.

My only experience in this is a Physics degree btw ;)
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Yes, but we all know anyone with a Physics degree is devoid of common sense :p.

You say the air being shot out of the back of the engine is producing thrust, which causes the plane to move forward, achiving lift and then take off.

Since people are wondering how to define the problem, I will offer one. Inherent in the concept behind the question is that the treadmill is there to stop forward momentum. If the plane could move on the treadmill, relative to the ground, then there would be no point in setting the question to begin with - this is how planes normally take off (incidentally assuming the hypothetical treadmill was able to keep up with the plane, I do not see how any absolute forward momentum would be possible).

So, the problem is that there is no forward momentum relative to the world, only to the treadmill. I do not see how the air being pushed out of the engine matters. Surely it is a question of sufficient speed/mass (or whatever) of air passing around the wing. This next bit I am unsure about. I would imagine that if the plane has no absolute forward momentum, relative to the world there would be little (or insufficient) air passing around its wings. Without this there would be no lift, and it would not be able to take off. It is not as if the treadmill has its own internal 'windtunnel' of which the air is faster than the surrounding airstrip.
 
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 the opposite direction). Can the plane take off?

That sentence is stupid if the conveyor belt is moving at the same speed as the plane the planes wheels will be turning on the stop. Try running at 5.5 MPH on a treadmill that's set to 5.5 MPH see how far you move. Feel the wind beneath your wings. LOL
 
andyp said:
It's not though is it? The wording in the OP is meant to deceive, so the question itself lacks any credibility.

If the question were simplified to what it's really getting at, without any of the trimmings - the answer quite simply is "if it has enough velocity, yes - if it lacks enough velocity, no"

There's no need to dress it up.

If you want to test yourself on the basic laws of physics, go take a GCSE Physics exam.
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Well done on still trying to save face.

The question is not ambigious, it's pretty clear in its description. The conveyor belt does move backwards proportionate to the speed the plane is moving forwards. The problem people have is that they assume a planes wheels are driven, or that the wheels are somehow relevant to the planes movement.

Disregarding the tolerance of the wheels themselves it wouldn't matter if they were rotating forward, backwards or sideways - or even to an extent if they rotated at all. Plane engines/propeller provides the forward thrust - ergo the wheels and by extension the treadmill are irrelevant.
 
jas72 said:
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 the opposite direction). Can the plane take off?

That sentence is stupid if the conveyor belt is moving at the same speed as the plane the planes wheels will be turning on the stop. Try running at 5.5 MPH on a treadmill that's set to 5.5 MPH see how far you move. Feel the wind beneath your wings. LOL
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Dude, have you read any of the other pages?

The plane is moving forwards from the trust from the engines, the plane doesn't move by using the wheels.
 
Durzel said:
The problem people have is that they assume a planes wheels are driven, or that the wheels are somehow relevant to the planes movement.

Plane engines/propeller provides the forward thrust - ergo the wheels and by extension the treadmill are irrelevant.
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I know all this -and your last point proves my point.

Fortunately I'm not the sort to deliberately over-complicate matters. A spade is a spade where I come from.
 
andyp said:
This needs to be (dis)proved as it has more relevance to the real world than some silly conveyor belt contraption.
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I'm afraid you are going to have to start a chimpanzee breeding programme urgently then as the best estimates I've seen put the numbers at somewhere less than 300,000 and probably significantly lower. I can't see too many conservationists being entirely happy about you strapping the entire population (and then some) onto the wing of a 747 just to prove a point that has nothing to do with the original question.
 
semi-pro waster said:
I'm afraid you are going to have to start a chimpanzee breeding programme urgently then as the best estimates I've seen put the numbers at somewhere less than 300,000 and probably significantly lower. I can't see too many conservationists being entirely happy about you strapping the entire population (and then some) onto the wing of a 747 just to prove a point that has nothing to do with the original question.
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But a lot of the original question has nothing at all to do with an aircraft taking off.

So it's swings and roundabouts.
 
andyp said:
This needs to be (dis)proved as it has more relevance to the real world than some silly conveyor belt contraption.
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Just accept that you are completely wrong and stop trying to avoid that fact by saying "its a pointless question anyway".

You sir are totally the guy at school who gets an F in science and says "I didnt want a good grade anyway"
 
If the plane is facing in the opposite direction of the conveyor belt then even it's its wheels aren't powered and it starts to pick up speed, it will be facing the wrong way. Planes aren't designed to take off backwards!?
 
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Durzel said:
Well done on still trying to save face.

The question is not ambigious, it's pretty clear in its description. The conveyor belt does move backwards proportionate to the speed the plane is moving forwards. The problem people have is that they assume a planes wheels are driven, or that the wheels are somehow relevant to the planes movement.

Disregarding the tolerance of the wheels themselves it wouldn't matter if they were rotating forward, backwards or sideways - or even to an extent if they rotated at all. Plane engines/propeller provides the forward thrust - ergo the wheels and by extension the treadmill are irrelevant.
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now you have me completely confused why do the planes need to travel at 180MPH to lift off? I would have thought that was to do with lift and not power produced by the engines. So even if the plane was on a conveyor belt it would still move foward despite the wheels having no forward traction?

If there is no air passing around the plane then how does it take to the skies. Surely Thrust alone cannot make a plane take off like a rocket? Unless it was pointed towards the ground?
 
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