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Originally posted by teal99camaro: dude, i'm in highschool and i know tis not possible for a plane with no ground speed to take off unl;ess there is a headwind that is strong enough to lift the plane.
Forget ground speed, forget lift, forget wings, forget. Would it move forward when the pilot engaged the JET engines (that use air for it's propulsion)?
Originally posted by airfrmr:
[qb] My point is your a dumba$$. bernoulli's principle is for fluid not air retard.
LMFAO [img]graemlins/rofl.gif[/img] [img]graemlins/rofl.gif[/img] [img]graemlins/rofl.gif[/img] [img]graemlins/rofl.gif[/img] How do you think a carb works? Venturi. Wow...
1995 Patriot Red T-Topped Z28 A4<br /><br />Mystery rebuild in progress.<br /><br />Soon to have 383 ways to beat KBreezy and Shane. :D
Mike, Matt, Jeff, I and a few others are the only smart ones eh?
Bummer.
You guys are totally stuck in "car mode" and thinking about this from a car standpoint.
You need to understand how thrust works, and how it is physically impossible for a damn treadmill to counteract thrust.
Its all so very clear.
Originally posted by teal99camaro: the treadmill counteracts the jet's propulsion [img]smile.gif[/img]
You need to go back and re-read the last 7 pages. The treadmill doesn't do ****.
Originally posted by teal99camaro: my friend whose a junior at embry riddle aeronautical engineering school says you're wrong.. hes an aeronautical engineer major
Who gives a damn where he goes to school? I'm a senior at the same school, and it doesn't matter to you. You friend is wrong.
Originally posted by Merlin:
Want more proof? Go run in a treadmill and stretch out your arms like wings and tell me if you feel air flowing over and under your arms. The answer is NO.
The plane is not like running!!!!!!!!!!!!!!!!!!!!!!!!!!
Originally posted by Merlin: No it is not, ultimately what matters is the effective speed over the wings. PERIOD. Unless he is using the jet engines to affect the flow over the wing through a suction or blowing.
There's plenty of wind, because the plane is moving normally!
What I learned from Old Hack was that an updated version of a question aimed at confusing folks over relative measurements of airplane motion and the medium in which it operates had shown up on the Internet, and it was causing the fracas in the Lounge.
The question that has been going around is not particularly artfully worded, and I think that has caused some of the disagreements, but I'll repeat it as it is shown: "On a day with absolutely calm wind, a plane is standing on a runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. The conveyor has a control system that tracks the plane speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction). Can the airplane ever take off?"
My comment: Notice that the question does not state that the conveyor's movement keeps the airplane over the starting position relative to the ground, just that it moves in the direction opposite to any movement of the airplane.
Initially, about a third of the folks here said that the airplane could not ever takeoff, because the conveyor would overcome the speed of the airplane and it could never get any airspeed. The rest said the airplane would fly.
The "It won't fly, Rocky" group said that the conveyor would hold back the airplane. They asked us to imagine a person running on a treadmill. As he or she sped up, the treadmill would be programmed to speed up, just as the conveyor in the problem, and the person would remain over the same locus on the earth, while running as fast as possible.
The argument was that if the airplane started to move forward, the conveyor program was set up to move the conveyor at exactly that speed, in the opposite direction, thus, the airplane would never move relative to the ground, and, because the air was calm, it could never get any wind over its wings. One of the analogies presented was the person rowing at three mph upstream in a river on a calm day. However, the current was flowing downstream at three mph, so the resultant speed with reference to the stream bank and air was zero, and thus there was no wind on the rowboat.
I watched and listened to the disagreement for a while and was fascinated to see that the argument seemed to split between those who had some engineering or math background, all of whom said the airplane would takeoff and fly without any problem; and those with some other background, who visualized the airplane as having to push against the conveyor in order to gain speed. Because the conveyor equaled the airplane's push against the conveyor, the airplane stayed in one place over the ground and in the calm air could not get any airspeed and fly.
It was an interesting argument, but as things progressed, more rational heads prevailed, pointing out that the airplanes do not apply their thrust via their wheels, so the conveyor belt is irrelevant to whether the airplane will takeoff. One guy even got one of those rubber band powered wood and plastic airplane that sell for about a buck, put it on the treadmill someone foolishly donated to the Lounge years ago, thinking that pilots might actually exercise. He wound up the rubber band, set the treadmill to be level, and at its highest speed. Then he simultaneously set the airplane on the treadmill and let the prop start to turn. It took off without moving the slightest bit backwards.
Basically, It explains why we are right, and you guys are wrong...
Engineering rules! :D
Originally posted by AZ3.8Camaro: Mike, Matt, Jeff and a few others are the only smart ones eh?
Bummer.
You guys are totally stuck in "car mode" and thinking about this from a car standpoint.
You need to understand how thrust works, and how it is physically impossible for a damn treadmill to counteract thrust.
Its all so very clear.
THANK YOU!
And to think there's a physics teacher and several engineers out there dumb enough to think otherwise.
I will prove it tonight with my truck, a winch, a tree, my reverse gear and icy roads. The winch & tree will act as the jet engine (a force producing device that it not affected by anything on the ground), the reverse gear will act as the treadmill effect and the icy roads will act as the "free wheel" effect that airplanes landing gear have. I will video tape it and put it up here.
Most of the nay-sayers still won't get it, or if they do they won't admit it.
You guys all say the plane won't move, but where's your proof? You can't show any! We have all the proof laid right out in front of you, but you can't show anything back except by comparing it to someone running on a treadmill.
Originally posted by BLLDOGG: the reverse power would be overcomed by the engine, not matched
The treamill can apply a speed to the wheels of the Jet, but speed and force are two very different things. Plus the bearing in the wheels prevent that wheelspeed from affecting the plane.
1997 Chevrolet Camaro v6 - 13.8@104MPH
1997 Dodge Viper GTS
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