View Full Version : Can someone answer this question?
Scottwax
11-26-2005, 09:43 PM
A plane is standing on runway that can move (some sort of 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 question is:
Will the plane take off or not? Will it be able to run up and take off?
Setec Astronomy
11-26-2005, 09:57 PM
No, it won`t, because it`s airspeed is zero.
Mike-in-Orange
11-26-2005, 10:12 PM
No, it won`t, because it`s airspeed is zero.
Dead on. The wheels may be spinning but without proper airspeed over the wings it will never generate lift and therefore never leave the ground.
Similarly, in theory, if you tethered the plane so it couldn`t move and placed in front of it a fan large enough to move the needed air over the wings to generate lift, the plane would get off the ground yet still not move due to a lack of forward thrust.
imported_DARKSTI
11-26-2005, 10:38 PM
yeap it wont be moving againt the air so it cant create lift or drag.
SpoiledMan
11-26-2005, 11:09 PM
Yep, no lift, no flight.
Black240SX
11-26-2005, 11:33 PM
Another question. If you had a big-*** wing on your car and were going fast enough, could you drive on an inverted road?
imported_DARKSTI
11-26-2005, 11:38 PM
Another question. If you had a big-*** wing on your car and were going fast enough, could you drive on an inverted road?
if you had enough power and were light enough. F1 cars are thought to be able to do it. But they are super light and have lots of power and down force.
SpoiledMan
11-26-2005, 11:48 PM
If it generates enough down force to exceed it`s weight it should, in theory, be able to invert.
Scottwax
11-27-2005, 12:08 AM
The question was first posted on a physics forum http://forum.physorg.com/index.php?showtopic=2417&st=0 and they can`t agree on the answer.
Black240SX
11-27-2005, 01:31 AM
lol
I originally thought that it would not take off, but after reading some of the 14 pages on the subject at the physics forum, I`ve changed my mind. It will take off!
SpoiledMan
11-27-2005, 02:03 AM
After rereading the question and taking a look at the forum, I was under the wrong impression. I didn`t understand that the plane would be using engine power and because of that the wheel speed doesn`t matter. Yes, it will take off.
wlhump
11-27-2005, 08:31 AM
The fact that the "ground" is moving the the opposite direction is moot. The airplane is reacting to the fact that the jet is creating thrust out the engines. The wheels are not powered and therefore do not need to interface with the ground in the smallest amount. In essence, the wheels only hold the plane up and reduce the friction of it as it moves down the runway.
Think about it this way.... The plane is already airborne. This eliminates the entire effect of the "moving runway." Does it fall out of the sky? Of course not because the thrust created by the expulsion of the hot gasses out the back of the engines are greater than the resistance to move the plane forward. Newton`s law: "For every action, there is an equal and opposite reaction" is what drives the plane forward. A moving runway has nothing to do with the scenario.
I have to go to this physics forum and see the arguments. It should be interesting.
JeffM
11-27-2005, 08:47 AM
Its irrelevant.
Planes take off on pavement.
Scottwax
11-27-2005, 09:09 AM
There are two threads about this on off topic. One is 129 pages long, the other is 53 pages!
Lowejackson
11-27-2005, 10:07 AM
if you had enough power and were light enough. F1 cars are thought to be able to do it. But they are super light and have lots of power and down force.
A F1 car would have no problems but the difficult part would be getting enough speed for the aerodynamics to come into play. The mechanical grip of an F1 car is not that high