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View Poll Results: Will it take off?
Yes 7 35.00%
No 13 65.00%
Voters: 20. You may not vote on this poll

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Old 01-27-2007, 03:32 AM   #1
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Talking See how smart you guys really are?

A plane is standing on a runway that can move (some sort of variable speed 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 plane is not a harrier or osprey


The question is:

Will the plane take off. Yes or No?
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Old 01-27-2007, 03:39 AM   #2
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well...

I hate riddles,but I'm bored...so I think the plane may take off, but it might not be able to continue its flight(unless its on the ground)
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Old 01-27-2007, 04:01 AM   #3
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That doesnt make much since but you have to give reasons why
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Old 01-27-2007, 04:14 AM   #4
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I say no. Not sure if it's a riddle and the answer turns out to be that the plane didn't have any fuel. Logically, however, the plane needs speed to create lift, so it's like running on a treadmill; there's no wind, so it's not getting lift.
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Old 01-27-2007, 04:48 AM   #5
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I'm going to say no just because there's got to be something not right with that.
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Old 01-27-2007, 05:05 AM   #6
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Yes. Common sense would tell you that if the conveyor is moving in the opposite direction, it will act just as if the plane were moving forward. The wheels will turn (normally), speed up and take off.
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Old 01-27-2007, 05:18 AM   #7
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The wheels will go twice as fast but that's about it, i.e. the plane will take off as normal (maybe a bit more thrust due to wheel bearing friction)?
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Old 01-27-2007, 05:31 AM   #8
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Quote:
Originally Posted by Enthusiast
A plane is standing on a runway that can move (some sort of variable speed 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 plane is not a harrier or osprey


The question is:

Will the plane take off. Yes or No?
That is a moronic question on many levels that you obviously gave little thought or effort to and cannot be answered as posed. Why?

1. Because we don't know which direction the aircraft is moving, we can't draw a conclusion if it will take off. If said aircraft is moving in reverse we know it won't take off.

2. Before you start typing, wait. One reason we don't know which direction the aircraft is moving in is because we don't know it it's moving under its own power or being pushed/pulled. Once again you expect us to guess before we can draw a conclusion.

3. Assuming the aircraft is moving forward, we still don't know if it'll ever gain enough airspeed to takeoff, because among other reasons...

4. We don't know what type of hypothetical aircraft we're talking about, except that it's not a Harrier or Osprey. On the other hand, it could still be some sort of VTOL aircraft (thank you Nikola Tesla) because there are literally hundreds of designs. But I digress...

5. And that airspeed is an extremely important factor in whether or not the aircraft will rotate. After all, a Piper Cub will rotate at about 60 mph where an SR-71 needs an airspeed of, well I don't know if that's been declassified so I'd better not say anything more than FAST. And yes, I have experience working on Habus.

6. We also don't know at what speed or what direction the wind is blowing in relation to the aircraft. There's a reason the aircraft always takeoff into the wind, or as close as possible to it.

7. So as you can see, I could keep going for day picking apart this feeble attempt at a question, but here is the answer you're most likely looking for.


Assuming that the aircraft is moving forward, and assuming the flight controls are positioned for takeoff (takeoff trim), and assuming the aircraft is under it's own power, and assuming it's not over the max takeoff weight, and assuming that all other flight parameters are met, the speed of the runway (or lack thereof) has nothing to do with if the aircraft will rotate and fly. Ground speed is immaterial as is wheel speed. The only thing that matters if everything else is in place is airspeed, and a moving runway does not provide airspeed. Happy?





Now I have a question for you. Is this for your third grade science project or what, because that's about the level of difficulty of this question?


P.S. You forgot one answer on your poll. Make one that says "This is a stupid question that can't be answered because the person asking it has no f*cking clue."
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Last edited by vwhobo : 01-27-2007 at 05:34 AM.
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Old 01-27-2007, 05:36 AM   #9
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Thinking about this question on a deeper level is hurting my neurons. My head hurts. I never liked word problems. I always end up with more questions than answers. Now I'm going to be thinking of this in my sleep.

Digressing...I'm missing key elements of the question here. Are you asking if the plane would take off on it's own just by being on the conveyor belt or are we to assume you are asking if just by being on the conveyor belt would make the plane take off. You need thrust to actually take off, right? But I keep reading this problem and then second guessing myself. If the plane is moving in one direction and the conveyor in the other at the exact same speed, the plane would be fixed in one spot, but would there be enough forward thrust to take off? Screw it, I'm going to bed.
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Old 01-27-2007, 07:25 AM   #10
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This question has been debated many times on TEH INTARWEBS, and the answer is always that it won't take off. Simply put, the plane is technically not moving, which means there is no air going under the wings at high speeds to create the lift. The wheels have no bearing on takeoff, being that they do not actually provide any propulsion, they just allow the plane to be moved by the engine's thrust, which creates the windspeed under the wings, so if the plane is not moving, no take off.
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Old 01-27-2007, 08:03 AM   #11
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Of course the plane would move and takeoff, the ground has nothing to do with thrust or air displacement.
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Last edited by Wally : 01-27-2007 at 08:05 AM.
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Old 01-27-2007, 08:29 AM   #12
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i say no!
a plane needs air under the wings to provide 'lift'!
(i havnt read other peoples remarks so if its similar,,,,coincidence!)
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Old 01-27-2007, 08:30 AM   #13
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Quote:
Originally Posted by Wally
Of course the plane would move and takeoff, the ground has nothing to do with thrust or air displacement.


The plane isn't moving... it's technically sitting motionless. The thrust produced by the engines is what provides forward movement, not the wheels, and since whatever thrust is being produced is being matched by the conveyor belt running in the opposite direction, the plane isn't moving forward, thereby not "gathering" air under it's wings.
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Old 01-27-2007, 08:35 AM   #14
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If the conveyor is moving at one speed one way, and the the plane is moving the opposite direction at the same speed, then of course it won't lift off. The plane is standing still with its wheels moving frantically.
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Old 01-27-2007, 09:29 AM   #15
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Are you guys for real? What are the wheels on a plane for? That's right they are there to reduce friction. The condition clearly states the conveyor moves in an opposite direction to the plane, unless the brakes are lock on, the wheels will merely rotate faster.

Think of you with a piece of string attached to an object with wheels on a conveyer moving counter. The object will stay where it is because the string restrains it. When you pull on the string the object will move forward with about the same effort as with a stationary conveyor, only the friction of the wheel bearings adding extra drag.
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Last edited by Wally : 01-27-2007 at 09:45 AM.
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