Plane on conveyer: Will it ever take off?
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From: SoCal
Originally Posted by VoIPA,Dec 6 2005, 08:48 PM
Ok, here's my semi-educated guess: the VCR will obviously move forward, perhaps crushing your skull in the process, but the helium-filled balloon will actually move towards the rear of the car (in the car's frame of reference). As the car decelerates, air pressure at the front of the car increases. Helium weighs less than air, being less dense, and the increased pressure at the front of the vehicle will actually push the less dense balloon backwards. The same effect can be observed when driving with Britney Spears.
BTW, the answer to the previous question is that the plane does not need to hold up the bird as the bird is creating its own lift. Those that guessed that the forces of the bird's wings act in micrscopic amounts throughout the plane are incorrect. If a plane flies over your head at more than the "boundary layer" number of feet where you would feel turbulence from the motion, you do not, even microscopically feel a downforce from the plane. I got this wrong on the test in college and now I design things that you buy. Scary, huh?
Mike
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From: La La Land
Originally Posted by Ubetit,Dec 2 2005, 07:53 PM
I have a remote control airplane and a treadmill. I'll do an experiment and get back to you!
Okay i'm back. The plane will take off like normal like Tedow says.
Okay i'm back. The plane will take off like normal like Tedow says.
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From: Covington WA, USA
Originally Posted by mistressmotorsports,Dec 7 2005, 04:21 PM
If a plane flies over your head at more than the "boundary layer" number of feet where you would feel turbulence from the motion, you do not, even microscopically feel a downforce from the plane. I got this wrong on the test in college and now I design things that you buy. Scary, huh?
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring;
There shallow draughts intoxicate the brain,
And drinking largely sobers us again.
Drink deep, or taste not the Pierian spring;
There shallow draughts intoxicate the brain,
And drinking largely sobers us again.
An airplane pushes down on the atmosphere the same way a boat pushes down on the ocean.
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From: Covington WA, USA
Originally Posted by magician,Dec 6 2005, 01:23 PM
First, a helicopter of any reasonable size cannot have a rotor spinning at 2,000 rpm. If the blades were, say, 10 feet long, the tip of the blade would be traveling at 1,428 mph - well over Mach 2 - and the blades would shatter; a helicopter cannot have the tips of its blades exceed Mach 1 without being destroyed.
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From: Covington WA, USA
Originally Posted by exceltoexcel,Dec 7 2005, 05:23 PM
usually rotors aren't as strong as plane wings, none the less I doubt they hit mach
You are correct that the design of the wing structure has some relevance, and you have to watch out for buffet and flutter. But it would be quite possible to spin the blades so that the tip mach number was supersonic. Jet engine blades have supersonic tip mach numbers, for instance.
But slower speeds are more efficient.
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From: Huntsville
Originally Posted by mikegarrison,Dec 7 2005, 07:19 PM
WTF? Do supersonic airplane wings "shatter"?
I have no idea what forces at that pressure are present (when it comes to physics, I know a lot more about optics than fluid dynamics), but I suspect it could cause issues.
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From: Covington WA, USA
Originally Posted by VoIPA,Dec 7 2005, 05:52 PM
Well, I can see how the tips exceeding mach 1 might be a problem. Airplane wings only move forward, but helicopter rotors spin meaning the blades could be potentially in contact with an ever increasing shock wave of air from the blade preceding it.