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  1. Join Date
    Sep 2005
    Posts
    3,005
    #81
    Ang bilis humaba ng thread ni Doc ah! hehehe!

  2. Join Date
    Jul 2006
    Posts
    3,601
    #82
    Ayoko na sumagot dito, paulit ulit na ang sinasabi eh...

    Oo nga eh, Doc kasi...

  3. Join Date
    Dec 2004
    Posts
    1,310
    #83
    Quote Originally Posted by kinyo View Post


    Above is the free body diagram of the plane's wheel showing the forces acting on it.

    W is the plane's weight.
    Ff is the plane's thrust from the engine.
    Fn is the normal force from the ground.
    Fb is the backward force due to friction from the ground.

    Fn is equal to W, hence there is no vertical motion.

    If the runway is not moving, Fb is insignificant and Ff will cause the plane to move forward. This case is just as good as when the runway is frictionless.

    If the runway is moving exactly as the plane would have moved if the runway is stationary, then it means that Fb is equal Ff and there will be no forward motion of the wheel, hence the plane does not move and will not take off.
    Ah, your FBD is incomplete and your analysis is completely wrong.

    Major flaw: The runway friction and engine thrust spin the wheels in the SAME direction, not in opposite directions. Try mo pa sa matchbox on a tablecloth. The only opposing force acting on the wheels is the friction of the wheelbearings, which is constant (unlike engine thrust) as well as negligible.

    We're not concerned about forces acting on the wheels, we consider the forces acting on the plane itself. The big force acting against the plane is wind resistance, not friction from the ground. Remember, the wheels are designed to freewheel.

    It's not the runway that's frictionless, it's the wheel bearings as far as this problem is concerned.

    Again, runway speed = plane speed (for the nth bloody time) does NOT imply runway force ACTING ON THE PLANE = engine thrust.
    Last edited by Alpha_One; November 10th, 2006 at 06:58 AM.

  4. Join Date
    Oct 2002
    Posts
    2,743
    #84
    plane's speed and tunes the speed of the conveyor to be exactly the same

    Will the plane be able to take off?

    NO!...simply because the airplane is stationary
    no thrust=no drag=no lift

    OT:

    which place will the airplane needs more longer runway during takeoff..in Baguio City or in Manila? heheeheheh
    Last edited by ozcity; November 10th, 2006 at 07:30 AM.

  5. Join Date
    Apr 2006
    Posts
    375
    #85
    At first, the obvious answer is: 'No, the plane won't fly.' But it's incorrect, the plane WILL fly. The simplest answer is because the plane's engines work on a different medium (air). Regardless of how fast the conveyor turns, the plane's engines would still be able to pull air into it which makes the air move across its wings which in turn will cause lift and let the plane take off. The only effect the conveyor belt will be is to cause the plane's wheels to spin a helluva lot fast.

  6. Join Date
    Apr 2006
    Posts
    375
    #86
    Quote Originally Posted by ozcity View Post
    plane's speed and tunes the speed of the conveyor to be exactly the same

    Will the plane be able to take off?

    NO!...simply because the airplane is stationary
    no thrust=no drag=no lift

    OT:

    which place will the airplane needs more longer runway during takeoff..in Baguio City or in Manila? heheeheheh
    Baguio City. Because the air's thinner up there. The plane will need a longer runway to be able to generate the lift necessary to fly.

  7. Join Date
    Jun 2005
    Posts
    345
    #87
    edit: fly...
    Last edited by knight23; November 11th, 2006 at 03:53 AM. Reason: i'm dumb

  8. Join Date
    Jan 2005
    Posts
    1,416
    #88
    Parang taong nasa threadmill yan kada hakbang niya or exert niya ng effort to move forward gumagalaw ang tinutungtungan niya kaya stationary siya, at sa case ng aircraft kahit ano ang lakas ng thrust ng engine to move forward stationary parin ito, at to create lift kailangan mo ng differential pressure between upper surface ng wing and its lower surface ng wing, dahil sa structural design ng wing naachive ito plus ang wind flow sa wing, since stationary ang aircraft walang napropoduce na wind flow sa wing, kaya ng ang runway ginagamit para maachieve ng aircraft ang certain speed ng wind flowing sa wing nito for lift, since no flow ng wind sa wing NO LIFT

  9. Join Date
    Oct 2005
    Posts
    74
    #89
    Ang aircraft Basta may lift , at thrust sympre aagat yan sa lupa lilipad siya. Heto ang barko lumulutang sa tubig ang aircraft naman lumutang sa hangin kaya pag no air di siya makakalipad except kong rocket, propelled ang lumupad.

  10. Join Date
    Aug 2004
    Posts
    22,710
    #90
    AGH!!!! HINDI KAYO NAGBABASA!!!!

    *knight23 and the others:

    [size=4]FORGET THAT THE PLANE HAS TO FLY. THE QUESTION IS, CAN IT MOVE FORWARD AGAINST THE CONVEYOR?[/size]

    Velocity does not count in moving the plane. Force does. If the airplane can move forward relative to the air, then the air will be flowing under its wings. Then it will take off.

    For the last time:

    Put a matchbox car on a smooth treadmill. Exert a tiny amount of force on the car to hold it in place. Run the treadmill at 10 miles an hour. Now, the treadmill is exerting something like 10 Newton-meters of force (don't know exactly how much, but that's a guesstimate) on itself to push the car backwards, but you can still hold it in place without pressing down harder with your finger.

    Why? Because, YOU are not on the treadmill.

    Your finger is the air. The airplane's engines are pushing against the air, NOT the treadmill. However damn fast the treadmill goes, the air above it stays perfectly still. Thus, the airplane can still push itself against this air even if the treadmill is going infinitely fast.

    Now, [size=4]go to your local gym, bring a matchbox car, and run it on a smooth treadmill. Come back here and tell us if you had to press harder as the treadmill sped up.[/size]

    Or, if you don't like such "unscientific" testing, bring a torque wrench with you. The matchbox, pressing on the torque wrench, will create a pressure reading. See how far it goes up as the treadmill goes faster... agh. For the treadmill to stop the plane, it would have to exert ten times as much force on the car at 10 mph as it does at 1 mph.

    I'm serious... [size=4]GO OUT AND DO THIS RIGHT NOW[/size].

    [size=1]Curse you, Doc OTEP! You've brought a curse upon us all!!!! They'll never understand!!! :evil:[/size]
    Last edited by niky; November 10th, 2006 at 11:06 AM.

    Ang pagbalik ng comeback...

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Will the Airplane Fly??????????