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Airplane on a Conveyor Belt - Exclusive Photos!
Discussion: Irrelavent
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lumpylizard lumpylizard |
Irrelavent
Jan 30 2008, 10:09 PM EST Of all the myths ever tested on Mythbusters “Plane on a Conveyer Belt” was by far the most ridiculous and irrelevant. Of course the plane took off, even though the belt was moving in the opposite direction the plane was still moving forward. I would bet anything that if you too the trucks speed at take off and subtracted the planes instrumental speed at take off the difference would be greater than the planes required take off speed. The whole premise of the myth was that the plane remained stationary, which it clearly didn’t. The myth is not busted, your method is busted. 21 out of 32 found this valuable. Do you? |
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craigiest craigiest |
RE: Irrelavent
Jan 31 2008, 1:21 AM EST If the plane has to remain stationary, how is it moving the same speed as the conveyor belt? The conveyor belt was moving 25mph and the plane was moving the opposite direction at 25mph airspeed, 25mph groundspeed, which is 50mph relative to the belt. 0 out of 4 found this valuable. Do you? |
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nate256 nate256 |
RE: Irrelavent
Jan 31 2008, 1:39 AM EST If the wheels are taken off the plane this will achieve the zero ground speed needed for this experiment. 0 out of 4 found this valuable. Do you? |
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craigiest craigiest |
RE: Irrelavent
Jan 31 2008, 2:10 AM EST The problem doesn't say anything about zero ground speed, and the idea that it's part of the problem results from misunderstanding (or poor presentation) of the problem. You don't need a conveyor belt to see that a stationary plane won't fly, you just need brakes. 0 out of 3 found this valuable. Do you? |
 jtlmd |
RE: Irrelavent
Apr 19 2008, 6:34 PM EDT I agree with your points. Aside from the horrible spelling errors in these many posts (e.g., "irrelavent") and the frequent use of the contraction "it's" by many folks where the possessive pronoun "its" was meant, it has been an educational experience for me. And I have been a licensed pilot for 36 years with no takeoffs from any conveyor belts. Let's suppose a plane has a liftoff airspeed of 60 knots. Let's suppose the wind is zero. Let's suppose the conveyor belt is operating as specified in the riddle. What do you think the indicated airpseed will be a liftoff ? Easy: 60 knots. But what do you think the airpseed will be, say, 2 seconds before that ? 0 out of 1 found this valuable. Do you? |
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sportshooter sportshooter |
RE: Irrelavent
Apr 20 2008, 2:24 PM EDT "I agree with your points.If the conveyor belt is operating as specified in the riddle (as you put it), it would be moving backward at the exact forward speed of the airplanes forward thrust in relation to the BELT (not the ground) which would mean the plane would be stationary in relation to the surrounding air and ground. Its airspeed would be 0 and it would not lift off. The only way it can lift off at that point would be to accelerate to a speed FASTER than the belt moving in the opposite direction, thus increasing its ground speed and airspeed (the same because the relative wind is 0) to a point equal to or greater than its rated take off speed to achieve flight which is what they did on the show. They didn't prove or disprove the myth on the show. All they did was prove an airplane has the capability of accelerating to an airspeed greater than 25 mph on a moving belt. 1 out of 1 found this valuable. Do you? |
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craigiest craigiest |
RE: Irrelavent
Apr 20 2008, 3:40 PM EDT You don't get it. Most versions of the riddle are AMBIGUOUS. People decide what the answer is based on their initial interpretation, then say the myth says something that isn't really there that yields their answer. Here's how the mythbusters phrased it: "Can an airplane on a conveyor belt running in opposite motion to the airplane's tires at the same speed keep the plane from taking off?" It doesn't say whether the conveyor belt is running "at the same speed" as the tires or the plane. The human mind often deals with ambiguity by selecting a meaning and ignoring the existence of the other possibility. When you then restate the riddle, you add clarifying details that were not originally there to support your reading. That said, if we accept your version, it would take like 5% thrust to keep a plane stationary on the conveyor belt. Nobody would think a plane would take off without using the normal amount of thrust required for take off. You could even satisfy the requirements of your version of the myth without the engines on. Just tie a rope to the plane and run it out in front of the treadmill and tie it up so it doesn't go backwards. All you're doing is spinning the wheels--of course the plane won't take off. That doesn't seem like much of a puzzle or myth. It was also obvious that the plane would take off when it was allowed to get to takeoff speed, which was what was clearly going to happen with their set up. There is no myth, just two different scenarios with obvious, but opposite, outcomes, and one ambiguous question that can describe either scenario because it's lacking crucial details. It doesn't help that their version is just totally garbled besides being ambiguous. If you take out long modifying phrase that holds the set up, it asks, "Can an airplane...keep the plane from taking off?" You can't use physics to fix unclear writing! 0 out of 1 found this valuable. Do you? |
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sportshooter sportshooter |
RE: Irrelavent
Apr 20 2008, 7:34 PM EDT "You don't get it. Most versions of the riddle are AMBIGUOUS. People decide what the answer is based on their initial interpretation, then say the myth says something that isn't really there that yields their answer. Here's how the mythbusters phrased it: "Can an airplane on a conveyor belt running in opposite motion to the airplane's tires at the same speed keep the plane from taking off?""I take "conveyor belt running in the opposite motion to the airplane's tires at the same speed" to mean the belt is running in the opposite motion to the airplane's tires at the same speed of the tires. Otherwise, they could have said simply opposite the motion of the airplane and not specified the tires. If there is some other interpretation then the so called "myth" is totally pointless and a total waste of time but it's not the first time they have done so called "myths" that are strikingly obvious before they start. Either interpretation you use, the outcome is completely obvious. A plane with it's wheels going the same speed as the belt will not be able to lift off. That's clear. Likewise, any airplane can overcome the 25 mph belt speed to its takeoff speed. Also clear. So I guess the only conclusion is, it was a total waste of time and it's not busted as they said nor is it confirmed. Do you find this valuable? |
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EnderGT EnderGT |
RE: Irrelavent
Apr 21 2008, 10:44 AM EDT "Otherwise, they could have said simply opposite the motion of the airplane and not specified the tires.The original wording of the myth did exactly this: made no mention of the tires, and only specified that the speed of the belt was equal to the speed of the airplane, but in the opposite direction. An unfortunate rewording, attempting to make it clear that the plane did, in fact, have wheels and wasn't just sitting on its belly on the conveyor, that has only added more confusion and debate to this issue. Do this for me, if you will: Ignore the wording of the riddle, whether your version or my version or any version. Answer this question instead: Is a treadmill capable of preventing an airplane from accelerating? Can the treadmill apply enough drag on the plane to overcome the thrust of the plane's engine(s)? 0 out of 1 found this valuable. Do you? |
 martiandrifter01 |
RE: Irrelavent
Apr 21 2008, 11:45 PM EDT "Answer this question instead: Is a treadmill capable of preventing an airplane from accelerating? Can the treadmill apply enough drag on the plane to overcome the thrust of the plane's engine(s)?I've built several flying models over the years; none of them ever needed a conveyor belt, nor could such a device have prevented their flight, and most were powered by rubber band motors. If the belt were large enough and fast enough the boundary layer might have been sufficient to stop them, but they were just small models, not real planes. 0 out of 1 found this valuable. Do you? |
 Tessler |
RE: Irrelavent
Apr 30 2008, 9:34 AM EDT I have to be honest , I agree with what you're saying about their method. I am usually in agreement with the methodology which the Mythbusters team use, but not in this case. I see this as fairly simple physics to the note that a plane takes off via lift created by air-flow over the wing surface. If the plane is not moving forward ie any forward motion is cancelled out with the reverse motion of the conveyor then NO lift will be achieved ie it CANNOT take off! I can imagine that practically, this would be extremely hard to prove, however, the facts speak for themselves.. 1 out of 1 found this valuable. Do you? |
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EnderGT EnderGT |
RE: Irrelavent
Apr 30 2008, 10:03 AM EDT "If the plane is not moving forward ie any forward motion is cancelled out with the reverse motion of the conveyor"That's a pretty big IF right there... Just to be perfectly clear, no one at all is disagreeing with the FACT that with no airflow over the wings, no lift will be generated and the plane will not fly. The point you're missing is that the conveyor DOESN'T cancel out the forward motion of the plane. The plane WILL move forward (so long as it's allowed to TRY to take off - to throttle up it's engines). Treadmills simply don't work for objects that derive thrust from any mechanism other than contact with the ground. If you insist on arguing that the plane's speed must be measured via the plane's wheels, i.e. the plane's ground speed relative to the belt, then you are explicitly stating that the plane isn't allowed to try to take off. As soon as the plane tries to take off, i.e. thrust is generated, the plane will move forward relative to the ground underneath the conveyor, immediately causing the wheels to turn faster than the plane's ground speed relative to the conveyor, violating the terms of the riddle. A conveyor or treadmill simply cannot prevent the plane from moving forward. The plane will take off. 0 out of 1 found this valuable. Do you? |