RE: Can It Take Off??  
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RE: Can It Take Off?? - 1/10/2006 8:44:00 PM   
britbrat


 

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quote:

ORIGINAL: mesae


quote:

ORIGINAL: britbrat
...---and no baloney about bearing friction -- if you have a magic belt, you also have frictionless wheel bearings.


It IS going to fly.




OK, but how come the bearings have no friction but the belt does? And who's going to check with Einstein to see if the clock in the airplane runs slower than one mounted on the belt?


The belt has to have friction for the question to have any meaning at all (which it doesn't of course), otherwise the airplane would just slither along the belt without the wheels turning.

It will fly.

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RE: Can It Take Off?? - 1/10/2006 11:05:13 PM   
Strat2003


 

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Status: offline 		The requirement that the conveyor speed and the wheel speed be equal takes this question out of the realm or reality and puts it into the Kingdom of Trick Questions. If the wheel speed doesn't exceed the conveyor speed then the aircraft hasn't moved forward. It's like saying, "A B-17 bomber powered by four 1,000 horsepower engines running full throtle is held stationary on the runway by a single piece of 4 pound test monofilament fishing line. Will it be able to take off?"
That piece of line can't hold the airplane in place in the real world, but since we've stated that it does in our trick question, reality doesn't matter.
There's no way a conveyer belt can make a damn bit of difference in the takeoff of a real world airplane.........but it's not a real world question.

This thread has been the most collosal waste of time I've ever seen!

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RE: Can It Take Off?? - 1/10/2006 11:24:50 PM   
Liberator


 

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RE: Can It Take Off?? - 1/10/2006 11:50:18 PM   
air mail rcu


 

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quote:

ORIGINAL: britbrat


quote:

ORIGINAL: jamieduff1981

While most of you are right with regards to the physics you're all misreading the question.

The question includes a limit (which in reality would be impossible to enforce). Read the question again, understand that the limiting clause means that the wheels can never be allowed to move faster than the belt, and then appreciate that in reality, by opening the throttle you are breaking the rules of the question.

In order for the plane to gain forward speed, it's wheels must go faster than the belt in order for the wheels to make headway on the belt. No-body says airspeed is linked to the wheels.

The wheels are important because the question locks their speed to that of the belt.

Once again, by moving forward on the belt the question rules are broken.

This is physically impossible, and in real life the plane would move forward regardless, but as far as this question is concerned, the plane cannot move (through worded limitations, not physics).


As has been previously posted, not being able to move forward does not preclude take-off. The belt friction will generate a moving airstream that will eventually exceed the aircraft's stall speed. It will then be able to lift off & immediately accelerate in ground effect to actual flight-speed.

---and no baloney about bearing friction -- if you have a magic belt, you also have frictionless wheel bearings.


It IS going to fly.



Interesting. If the belt generates a airstream under the wing wouldn't that be a low pressure airstream? If so the wing would move towards the low pressure and the plane would stay on the belt.

Either way the plane does not fly.


< Message edited by air mail rcu -- 1/10/2006 11:55:05 PM >

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RE: Can It Take Off?? - 1/11/2006 3:56:38 AM   
mickeymouse23


 

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Status: offline 		The plane would fly becuse if you remember the wheels on a plane are flooting on a rod and the rod is stationary to the plane. The conveyer belt is one with the wheels and the plane is seperated from the wheels. The plane will move the landing gear struts forward and take off. For an experiment take a tredmill place the plane on it and start the tredmill and then push the plane forward (you are acting like the engine) the plane moves forward in relation to the ground that the tredmill is sitting on. Some smart people need to just realize that the KISS answer is sometimes the best. Just my 2 cents.

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RE: Can It Take Off?? - 1/11/2006 4:10:33 AM   
air mail rcu


 

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Status: offline 		The question stated the wheels can't move faster then the belt. If the wheels move forward then they are moving faster then the belt. Either with your finger or the prop does not matter. The plane can't move forward. If the plane CAN'T move forward it will not fly. K.I.S.S.

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RE: Can It Take Off?? - 1/11/2006 4:55:16 AM   
mickeymouse23


 

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Status: offline 		Yeah but in the math formula befor if the belt is moving 225 mbh then the whels are moving at a much faster rate so there ya go!

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RE: Can It Take Off?? - 1/11/2006 1:05:17 PM   
air mail rcu


 

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Status: offline 		The wheels can't move faster then the belt. That's it. Period. That's what the question states.

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RE: Can It Take Off?? - 1/11/2006 1:19:42 PM   
mesae



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quote:

ORIGINAL: air mail rcu

The wheels can't move faster then the belt. That's it. Period. That's what the question states.


"Imagine an airplane is on the beginning of a massive conveyor belt, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation.
There is no wind.

Can the plane take off?"

Does the original problem actually state that the wheels can't move faster than the belt? No. It DOES say that the belt is designed to match the speed of the wheels. Depending on how you look at the question, either there is some arbitrary and imaginary force holding the airplane back (opposing thrust), or the belt will be UNSUCCESSFUL at its DESIGNED task, and the plane will take off, despite the belt's rapid and continuous acceleration in an attempt to keep the airplane from moving with respect to the Earth.

Was the problem adapted from one involving a ground vehicle?

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RE: Can It Take Off?? - 1/11/2006 1:20:54 PM   
mulligan



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quote:

ORIGINAL: air mail rcu

The wheels can't move faster then the belt. That's it. Period. That's what the question states.


You are stuck in a Star Trek type space-time continuum temporal displacement thing...

Paradox: An assertion that is essentially self-contradictory, though based on a valid deduction from acceptable premises.

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RE: Can It Take Off?? - 1/11/2006 1:28:48 PM   
britbrat


 

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quote:

ORIGINAL: air mail rcu


Interesting. If the belt generates a airstream under the wing wouldn't that be a low pressure airstream? If so the wing would move towards the low pressure and the plane would stay on the belt.

Either way the plane does not fly.



Where would you get a wild idea like that? You can lead a horse to water --- but---

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RE: Can It Take Off?? - 1/11/2006 1:37:49 PM   
mesae



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RE: Can It Take Off?? - 1/11/2006 1:41:21 PM   
15thAF


 

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quote:

ORIGINAL: mesae



Does the original problem actually state that the wheels can't move faster than the belt? No. It DOES say that the belt is designed to match the speed of the wheels. Depending on how you look at the question, either there is some arbitrary and imaginary force holding the airplane back (opposing thrust), or the belt will be UNSUCCESSFUL at its DESIGNED task, and the plane will take off, despite the belt's rapid and continuous acceleration in an attempt to keep the airplane from moving with respect to the Earth.

Was the problem adapted from one involving a ground vehicle?


mesae, you are absolutely correct. Those who think that the question 'locks the wheel speed to that of the belt' have it exactly backwards. The question attempts to lock the belt speed to that of the wheels (huge difference) which, as explained about 7 pages ago, is physically impossible. Designed to and as built are two totally different concepts. The Edsel was designed to be a big seller for Ford, however, it failed miserably in application. Belt speed will always be based on a reaction to wheel speed, i.e. a change in wheel speed must occur first. Anyone who could successfully build a conveyor belt that could restrain the airplane in this question would make a fortune in the control system industry. Unfortunately, the pot of gold is safe.

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RE: Can It Take Off?? - 1/11/2006 2:34:58 PM   
Rat1



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quote:

ORIGINAL: mckeymouse

The plane would fly becuse if you remember the wheels on a plane are flooting on a rod and the rod is stationary to the plane. The conveyer belt is one with the wheels and the plane is seperated from the wheels. The plane will move the landing gear struts forward and take off. For an experiment take a tredmill place the plane on it and start the tredmill and then push the plane forward (you are acting like the engine) the plane moves forward in relation to the ground that the tredmill is sitting on. Some smart people need to just realize that the KISS answer is sometimes the best. Just my 2 cents.



Well if you read the question it says that the treadmill is designed to match wheelspeed at all times. Now if the aircraft is moving forward on the treadmill then its wheels are spinning at a greater velocity then that of the treadmill thus the rules of the question have been broken. If you stay within the boundaries of the question itself then the plane will not fly.

What doesn't matter is if a treadmill or conveyor can do this or not. This is not the question. Once some people get past that and just answer the question as it stands then things would be easier. There was some argument about skidding or sliding the wheels across the conveyor on another site and it was agreed that if this was possible then the aircraft would take off if we were only tracking the rolling velocity of the wheels and not the forward velocity.


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RE: Can It Take Off?? - 1/11/2006 2:37:30 PM   
exeter_acres



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RE: Can It Take Off?? - 1/11/2006 2:59:20 PM   
mesae

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