First of all, in your situation (which is just flat out stupid) the plane would not think that it is going 5 mph because a plane senses its speed using air flow NOT from speed of wheels. This shows you are missing more than just the basic premise of the question.

Secondly, the plane moves and thus your entire argument was pointless. Belt doesn't keep the plane from moving...understand this...please...or I will be sending someone over to pick up your ring.

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The runway only moves the wheels. Airplanes' wheels do not supply the thrust towards takeoff.

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If the plane were weightless, this argument would hold water, as it is, it does not.

The only reason the wheels move at all is because of the forward thrust of the engine. If the conveyor belt negates all of that thrust by moving in the opposite direction, then the engine thrust is being transferred to the conveyor belt and no forward motion is noted by the plane. No forward motion results in no lift, no lift = no takeoff.

However, even the slightest change in thrust angle to the vertical will cause the plane to takeoff. If the entire thrust of the engine is parallel to the conveyor belt, the plane remains stationary. (assuming of course that the wheel bearings can take the stress )

[This message has been edited by Dad-O-Lot (edited 12/4/2006 3:19p).]

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So the plane thinks it's going 5 mph.

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So what happens when the plane "thinks" it's going the speed at which it normally lifts off?

I'll give you a hint: The plane has an airspeed indicator, not a groundspeed indicator.

So, Goose, if someone turns a hi-speed fan on the pitot tube, does the plane think its taking off, or simply enjoy a slight cooling sensation?

This is the most boring thread in months.

DAMMIT PEOPLE FORGET WHAT THE QUESTION ASKED.



If the plane SITS STATIONARY with the belt going one way and the thrust the other IT DOES NOT TAKE OFF.

IF the plane is still moving forward at all ON THE BELT it DOES FLY. AS LONG AS IT REACHES TAKEOFF SPEED

THE QUESTION is worded HORRIBLELY

OK, throw out "the plane thinks" part. It was irrelevant anyway.

Rest still stands.

The question is worded poorly, but it still makes it quite clear that it is a test of whether you are thinking enough to understand that a airplanes propulsion comes from the engines and not the tires.....that is the ENTIRE POINT of this question and thus Kramer is an idiot.

I think some people are just waiting until it's 3:30.

Others, 4:20.

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The only reason the wheels move at all is because of the forward thrust of the engine. If the conveyor belt negates all of that thrust by moving in the opposite direction

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How is the conveyer belt transferring any force via free-spinning wheels?

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IF the plane is still moving forward at all ON THE BELT it DOES FLY.

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On this, I agree. however, the question said the belt matched the speed EXACTLY, which means that it doesn't move.

Even if the belt matches the speed of the plane, how does the belt keep the plane from moving forward?

At first, I thought all the people saying it would take off were just joking around and being stupid, but the more I read, the more I started to think these people are seious. so, just in case all these people really are serious, I will tell you what would happen (if the people were being dumb, I sound like a retard explaining this). An airplane does not fly because of how fast the wheels are turning, but how fast the air is moving over the wings. If the plane doesn't actually move because the conveyer is countering the forward motion from the wheels, no wind is produced, the plane just sits there, no lift is created. Jet engines produce a forward motion, this forward motion is what produces the airspeed over the wings, this airspeed over wings produces lift. If the forward motion is nullified, no lift created.

The belt matching the speed of the plane would only slow it down a little bit and it would be due to friction........why is this so hard to understand?

What "speed" is the belt matching?

If the plane is stationary, what is the plane's "speed"?

CopeIt,

You're which to throw out the difference in engines and wheeles, but you provide no evidence to back up your non-existant point.

Again, this isn't my answer, it's a retired Air Force pilot's.

You might want to watch the "idiot" talk, tough guy. No need for name-calling. Of course, I guess if you can't make a logical argument, name-calling is all you have left.

Nawlins...YOU ARE THE IDIOT. The plane moves and thus flies.

Let me slow it down for you. Y O U A R E A N I D I O T!

btw I am namecalling because I am sick of explaining this but am also appalled that we are being called morons for the CORRECT answer. I am not going to sit here and explain it "in logical terms" because it has been done a lot in this thread and if you haven't already understood, you probably wont.

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how does the belt keep the plane from moving forward?

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How does a jogger stay on a treadmill? Same principle. If the treadmill matches the joggers speed no matter how fast the jogger runs, the jogger will never run off the front of the treadmill.

forget it

[This message has been edited by Old Faithful (edited 12/4/2006 3:28p).]

There is no plane....





Thank you!

it was my understanding that the plane does not actually move, hence the conveyor system matching the speed of the turning wheels of the plane. it's exactly like a guy running on a treadmill, if you stand on the side and watch the guy run, he's running, but the treadmill is matching his speed, so to you, he's running in place. Last time I was on a treadmill running, I felt no air blowing in my face. This air blowing is what is needed to produce the lift. idiot

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So, Goose, if someone turns a hi-speed fan on the pitot tube, does the plane think its taking off, or simply enjoy a slight cooling sensation?

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That's the reason the pitot tube faces the same direction as the wing. So yes, if the air traveling into the pitot tube were sufficient that when compared to the static air it caused the airspeed indicator to show sufficient airspeed to take take off, then yes, the plane would take off.

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How is the conveyer belt transferring any force via free-spinning wheels?

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Magic. That is the "faith" part of the entire question. How does the conveyor belt match the speed of the wheels? How long is the delay? It is an impossible situation but an interesting thought experiment.

The question states that the conveyor belt matches the speed of the wheels. The speed of the wheels is in direct correlation to the thrust of the engine. It reads to me as if to posit that the conveyor belt's sole purpose is to keep the wheels stationary with respect to the surrounding ground (outside the area of the conveyor belt). I also assumed that the conveyor belt was stationary with regards to the surrounding area.

This is why the ice analogy is incorrect. The conveyor belt is not just a frictionless surface, it is a reactive surface.

This would be akin to pushing against a device that had the ability to match your force exactly. You could push all day and make no progress.

So, no the wheels do not provide the propulsion, but in our mythical situation they end up providing propulsion (in effect) to the conveyor belt.

Someone do a force vector diagram. Just a simple one with the force of gravity, the force of the propulsion, the lift and the reactive force implied by the situation where the conveyor belt reacts to the wheels turning.

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friction

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CopeIt,

Who said anything about friction? Where was this introduced into the equation. Oh it wasn't. So I guess you just made it up.

The question says the belt matches the plane's speed EXACTLY. Maybe they compensated for friction. Who knows.

The fact is that the plane never moves down the runway. The engines produce thrust. The tires spin. But just like a runner on a treadmill, it goes nowhere.

Oh, and this is one of the greatest threads of all time.

The belt matching the speed of the plane does NOT keep the plane from moving.

If the speed is measured by an observer on the ground then the plane flys. The conveyor won’t move if the jet isn’t moving.

Friction in the wheels is not a function of speed. Seeing as how every plane has enough thrust to overcome this friction the plane takes off.

Go back to an earlier post I made about how the people that are wrong argue the most, even in detail, about how the wrong answer is right. It's funny, because it's like a train wreck.

Kramer, Nawlins, etc. are proving this point. The plane flies.

no...its second best thread ever

fran needs a stache is the best

isn't it just like when you walk the opposite way on the airport people mover thing...your legs are moving, but in relation to the ground around you, you're still?

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The belt matching the speed of the plane does NOT keep the plane from moving.

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OK. Explain how it moves. Use the treadmill analogy.

I think the main point of misunderstanding is that the plane moves down the runway.

The people that think the plane doesn't fly think this is because the plane doesn't move. The plane moves. The plane moves, gets up to take off speed, and flies, no matter how fast the belt spins. The belt is irrelevant.

It is not at all like a runner on a treadmill.

action = reaction

Normal:

Action -- Thrust of engine

Reaction -- Plane moves forward

Mythical Situation:

Action -- Thrust of engine

Reaction -- Conveyor belt moves

The question is not worded poorly at all, nor is its point to see if you understand where the airplane's momentum comes from.

It is worded in a way to allow both sides to see their argument as valid, while seeing the other side as invalid. It is worded in a way to not allow for an exact answer due to the impossibilities depending on how you read it. Hence, lots and lots of arguing and no answer.