The plane will never move...it has no momentum (assuming the momentum of the wheels is negligible).
Mythbusters tackles the plane/treadmill
- Thread starter Pitbozz
- Start date
The plane will never move...it has no momentum (assuming the momentum of the wheels is negligible).
On LS2.com, they have a 1 year avatar bet on everyone who voted! Lots of folks want to change once they realize it will take off.
:tongue: :biggrin:
Here is how I see it, if the conveyer is going to match ground speed of the plane it wont fly. If it is going to match air speed then it flyies. Lets say the plane is going 100mph air speed and the conveyer is going to match it 100mph(200mph ground speed measured by the wheels) it's going to produce lift. The original question doesnt tell how it is going to measure speed it just says it be equal, equal to what AIR OR LAND
You need to think about what is ground speed? Is it relative to the dirt under the treadmill or the plane relative to the moving part of the tread mill. Either way really the plane will fly.
I think the video of the airhog in the rope through a soda straw really proves that it will fly.
Doesn't matter how you measure the 'speed' of the plane. Measure it anyway you want to. Hell, double the speed of the treadmill, triple it. It doesn't matter because:
The treadmill is irrelevant.
The treadmill is irrelevant.
The treadmill is irrelevant.
The treadmill is irrelevant.
The treadmill is irrelevant.
And I stand corrected as to how Mythbusters will do the conveyor/treadmill aspect. They are going to use a longass piece of tarp material and pull it by truck from under the plane in the opposite direction. It will still be the same effect as using a treadmill.
imjoesnuffy
I just break stuff!
- Joined
- Sep 13, 2005
I think it is hilarious that people get heated debating this subject. I voted no, maybe my understanding of the principles of flight are off but I thought it happened because of the following:
Lift occurs because the air moving under the wing is travelling faster than the wind going over the top of the wing.
How does a plane on a treadmill make this happen, with no wind travelling under the wing???
Using this same logic, a really powerful car on a dyno would not spin the tires on the dyno of it had a really big wing on the back
Maybe that is why ricers have those big wings, to increase the downforce, so they won't spin
Lift occurs because the air moving under the wing is travelling faster than the wind going over the top of the wing.
How does a plane on a treadmill make this happen, with no wind travelling under the wing???
Using this same logic, a really powerful car on a dyno would not spin the tires on the dyno of it had a really big wing on the back
Maybe that is why ricers have those big wings, to increase the downforce, so they won't spin
What does the ground have to do with wind?
The ground can do absolutely anything it wants, has no relevance to what the wings do.
You can fly a plane without moving relative to the ground at all.
If ground speed were important, there would be a ground speed indicator.
Look up cockpits online and show me a ground speed indicator. Please.
imjoesnuffy
I just break stuff!
- Joined
- Sep 13, 2005
I don't know where the ground comes into play with this, I didn't say anything about the ground
imjoesnuffy
I just break stuff!
- Joined
- Sep 13, 2005
Altimeter
An altimeter is an active instrument used to measure the altitude of an object above a fixed level.
The treadmill is only irrelevant if the it is referenced to equal land speed and not referenced to air speed. If it matches land speed then air speed will be Zero and no lift
no. they don't.
ground is irrelevant.
treadmill is irrelevant.
there ain't nothin left of this dead horse.
and BTW, if you "suddenly stop" the treadmill, once again, all you will do is change the speed of the wheels under the airplane. the tires might smoke a little due to the sudden change in speed and for the exact same reason they usually smoke when plane lands. (inertia tries to keep the wheels/tires spinning at the same speed)
SouthernCal GN
I come in peace....AK AK
- Joined
- Mar 18, 2004
This train wreck is going all over the place!
the question is irrelevant.
the question is irrelevant.
the question is irrelevant.
the question is irrelevant.
See, I can do it too :biggrin:
the question is irrelevant.
the question is irrelevant.
the question is irrelevant.
the question is irrelevant.
See, I can do it too :biggrin:
If the treadmill is going 100mph (ground speed) doensn't the plane need enough thrust to equal 100mph to sit still 0mph(no air speed-no lift). This is if the treadmill is referenced to ground speed. Now if you reference the treadmill to match the air speed of the plane it will take off and the treadmill will be IRRELEVANT
The engines of the plane are pushing air. The plane makes enough power to push it forward at 10MPH, if it was on a treadmill going 100MPH in reverse then the plane will go 10MPH forward ( minus a very little for wheel friction ) the plane wheels will be going 110in relation to the tread mill. You are missing the point that the planes engines push air and have no effect on the wheels that are on the treadmill.
[shaking head in frustration]
the wheels on the airplane disconnect the airplane from *any and all* lateral (in this case, front to back) forces the treadmill could possibly tranfer to the airplane (ignoring negligible wheel bearing friction). this is the same basic principle structural engineers use to isolate buildings and bridges from lateral forces of shifing ground.
take the wings (and lift) completely out of the equation for a moment. imagine you have the "rocket-car" Impala from a previous MythBusters episode on the treadmill. the cars engine normally propels the car forward with "tractive" force against the ground or road surface or in this case, the treadmill through the wheels and tires. In the case of the car, the speed of the treadmill has a *DIRECT* effect on the forward velocity of the car. if the cars speedometer reads 100 mph, but you're running the treadmill 100 mph in the opposite direction, the car will appear as though it's sitting still. if the speedo says 100 mph and you spin the treadmill at 120 mph, the car will actually have a *rearward* velocity of 20 mph. if the cars speedo reads 100 mph and you spin the treadmill at 80 mph, the car will actually be moving forward at 20 mph. Now....let's make it interesting and light that rocket (and hope it doesn't blow up like in the actual Mythbusters episode!) Once the rocket is fired it starts producing *THRUST* so now you have thrust forces acting on the car instead of or in addition to the tractive force of the wheels. Ok....follow me here...if the rocket is capable of producing enough thrust to propel the car to *ANY* speed *AT ALL*, be it 10 mph, 100 mph, 160 mph or even 300 mph, THE ROCKET ENGINE WILL PROPEL THE CAR TO WHATEVER FORWARD SPEED IT HAS THE CHEMICAL ENERGY TO DO SO REGARDLESS OF WHAT THE TREADMILL IS DOING!!
and you can picture a similar scenario with a car on a dyno. if you have a rocket-car or even a car with a jet or propeller engine on it, it does not matter how fast or slow the dyno is spinning, once you have some kind of thrust force acting on the car, it WILL move in the direction opposite the thrust. if it's only a little bit of thrust (small rocket) it may not move much, but if the thrust force is large enough to overcome the car's dead weight (inertia) then the thrust force will move the car regardless of what the dyno is doing.
First off, the altimeter does not measure forward speed relative to the ground. Has nothing to do with the speed of the ground relative to the airplane.
Secondly the altimeter does not know where the ground is, it assumes distance to sea level based upon atmospheric pressure change. Only a radar altimeter knows distance to the actual ground. A standard altimeter just sees distance to sea level. This is what most GA aircraft have. RadAlt is not common. The military aircraft I work on all have a standard altimeter. They also have radalt, but that isnt effective as a primary flying instrument. Radar altimeters cannot see terrain directly ahead of the aircraft, only that directly below it; such functionality requires either knowledge of position and the terrain at that position or a forward looking terrain radar which uses technology similar to a radio altimeter.
So you see that the standard altimeter really has no relevance to where the ground is or what it is doing. You can still fly into the side of a mountain with an altimeter. It will just tell you how tall the mountain was (provided you didnt fly into different atmospheric conditions)
I understand what you are saying, but the question says it is equal speed. Lets say the treadmill will go to whatever speed it takes to match the plane. I agree that if the treadmill cant keep up then it will fly, but that is not what the question ask or states. I think to answer this we need more details on how the speed is measured. I dont disagree with you I just think if the treadmill is respondind to air speed of the plane it will fly ,but if the plane is responding too speed of the treadmill to keep up/equal it wont fly.I think everybody is getting away from the EQUAL PART, but equal to what?