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plane question

Discussion in 'Off Topic [BG]' started by fr0me0, Jan 13, 2006.


  1. fr0me0

    fr0me0

    Dec 7, 2004
    Winnipeg Canada
    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: Will the plane takeoff?
     
  2. Vorago

    Vorago (((o)))

    Jul 17, 2003
    Antwerp, Belgium
    no
     
  3. fr0me0

    fr0me0

    Dec 7, 2004
    Winnipeg Canada
    i think it would still take off. I mean the conveyor would just spin the wheels backwards the wheels don't provide much drag on the plan cause the forward motion is from the thrust of the engine, not from the wheels themself.
     
  4. canopener

    canopener

    Sep 15, 2003
    Isle of Lucy
    Where's Ray Salamon when you need him?
     
  5. Gard

    Gard Commercial User

    Mar 31, 2000
    Greensboro, NC, USA
    General Manager, Roscoe Guitars
    Vorago is correct.

    In your scenario, the plane would never gain any forward speed at all, and without doing so, there will be no lift on the wings, the plane will just sit still.
     
  6. Kelly Lee

    Kelly Lee Yeah, I'm a guy! Supporting Member

    Feb 17, 2004
    Marana, AZ, USA
    The main thing an aircraft must have is "lift". It cannot get that unless the wings are moving through the air at sufficient speed to generate lift. Spinning the wheels to 10,000 mph will not give the aircraft any lift whatsoever. Sorry.

    EDIT: Dang it Gard, you beat me to it!
     
  7. SnoMan

    SnoMan Words Words Words Supporting Member

    Jan 27, 2001
    Charleston, WV

    Huh :confused:



    It takes upward lift caused by wind to get a plane off the ground.....not just making the wheels move....which is all what you originally proposed would do.
     
  8. Gard

    Gard Commercial User

    Mar 31, 2000
    Greensboro, NC, USA
    General Manager, Roscoe Guitars
    You'll have to settle for me for now, but I'm the son of a former USAF and Delta Air Lines captain, grew up spouting aeronautical equations.

    :)

    V sub 1, V sub 2, V sub r....

    ...where's that geek smiley???

    :confused:

    :D
     
  9. Yep. No forward motion-or air moving over the wings-no lift, no fly.
     
  10. fr0me0

    fr0me0

    Dec 7, 2004
    Winnipeg Canada
    ok put a model car on a treadmill and it goes backwards.

    Now hold it with you hand it will stay motionless with little effort. it'll also be really easy to move it forward no matter how fast its spinning since the only drag you have to contend with is the slight drag on the axels since there's no drive train (like on a plane)

    i think the thrust from a plane engine will be exactly like your hand since its a force external to the treadmill, I think the plane would move not matter how fast the conveyor was going.
     
  11. SnoMan

    SnoMan Words Words Words Supporting Member

    Jan 27, 2001
    Charleston, WV
    Wait Wait Wait!



    you've worded your original question very poorly.




    You're not asking it the plane will take off from the conveyor, you're asking if the plane will be able to move itself off the conveyor regardless of the conveyors speed.

    Whether the plane will fly is irrelevant, you want to know if the plane will be able to move itself off of the conveyor.


    Is that correct?



    I'll have to think about my answer again if that's what you're trying to get at
     
  12. fr0me0

    fr0me0

    Dec 7, 2004
    Winnipeg Canada
    its not actually my quesiton it was posted on another form I visit and has turned into a huge pissing match over there lol. The way I interpret the situation the spirit of the question is "will the plan be stuck in one spot or will it be able to move forward against the conveyor" wether or not the conveyor is long enouhg for the plane to get enough speed or not to take off is mute. More so the question is will the plane be able to move forward.

    people say that since the conveyor is matching speed the plane won't go anywhere, but how can its speed effectivly produce drag on the plane since the wheels on the plane aren't used to generate forward motion, the engines do.
     
  13. It'll just get really fast in a hurry.

    Since the conveyor is matching the plane's thrust, the plane will sit still with its wheels spinning. At least, until the conveyor breaks or runs out of power, and then the plane goes, and it takes off. (or the conveyor is stronger, and the plane quits, and gets thrown off) I'd put my money on the plane being stronger at the limit.

    Edit: Actually, the planes engine is fighting its own wheel friction. It's already known, for sure, that the engine can overcome THAT. Faster, faster, faster, conveyor goes boom, plane takes off.
     
  14. fr0me0

    fr0me0

    Dec 7, 2004
    Winnipeg Canada
    like theoretically I guess i'tll never take off but I mean thats one hell of a conveyor since the only drag on the plane its producing is wheel friction.
     
  15. ^^^^^

    I can't phrase it any better myself
     
  16. UnsungZeros

    UnsungZeros The only winning move is not to play.

    This is a situation where thrust vectoring would be nice to have.
     
  17. SnoMan

    SnoMan Words Words Words Supporting Member

    Jan 27, 2001
    Charleston, WV
    Ok, I have no physics knowledge....or any field of knowledge that pertains to this, I'm using just what I've picked up in my years.


    I assume that the plane may be able to move forward if it's engines are able to create enough forward propultion to offset the drag caused by the wheels(which will be influenced by the wieght of the craft).




    More-so, you would need to know the weight of the aircraft, the amount of surface contact from the tires, the hieght of the engines, the placement of the engines on the aircraft, the output force of the engines and possibly any variables caused by the material on the converyor belt.


    A formula could probably be divised using those measurements to give an exact speed/thrust-amount needed for the plane to move forward on the conveyor.




    I could be completely wrong....but I feel that I'm on the right track here
     
  18. SnoMan

    SnoMan Words Words Words Supporting Member

    Jan 27, 2001
    Charleston, WV
    and you can probably throw the word displacement somewhere into my variables also...something surely needs to be displaced.....
     
  19. fr0me0

    fr0me0

    Dec 7, 2004
    Winnipeg Canada
    i think whats interesting is how fast would the conveyor have to spin, to put enough friction on the axle's in order to negate the amount of thrust from the plane's engines. I really don't think theres a conveyor fast enough to do that
     
  20. It will fly.

    It will fly because it's pushing with the jet engines, not the wheels.

    Doofuses.