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  1. Join Date
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    #111
    o eto na, para matigil ang discussion! film evidence!! :bwahaha:

    :plane:
    :threadmil

  2. Join Date
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    #112
    Quote Originally Posted by M54 Powered View Post
    o eto na, para matigil ang discussion! film evidence!! :bwahaha:

    :plane:
    :threadmil
    O kitam? It's not moving! Stationary sila! hahaha

  3. Join Date
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    #113
    Quote Originally Posted by M54 Powered View Post
    o eto na, para matigil ang discussion! film evidence!! :bwahaha:

    :plane:
    :threadmil
    hindi nga lang opposite direction ung conveyor..kaya tama lumipad yung airplane..

  4. Join Date
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    #114
    Quote Originally Posted by mbeige View Post
    O kitam? It's not moving! Stationary sila! hahaha
    hehhe mali nga eh kasi the same direction yung conveyor sa airplane..
    lilipad nga yan..hahahaha

  5. Join Date
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    #115
    Quote Originally Posted by ozcity View Post
    hehhe mali nga eh kasi the same direction yung conveyor sa airplane..
    lilipad nga yan..hahahaha
    Pero di naman gagalaw yung airplane ah, nandun pa rin siya... naku eto na naman tayo

    TAMA NA!

  6. Join Date
    May 2006
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    663
    #116
    lol! nice engaging thread. actually better than the religion thread or chicken & egg thread(?).
    ako I go for the lift off possibility as well whether it's propeller driven or jet engined but never bicycle driven obviously. lesson in physics (relative velocities) and basic mechanics (aeronautics & fluid) should be able to explain this. plus those cute emoticons should be proof enough.
    now, anymore hair pulling puzzles for our forum gods sir thread starter(mr. wise guy)

  7. Join Date
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    #117
    Doesn't matter if he doesn't answer.

    The answer is actually obvious enough to anyone with an engineering or math background (I was a math wiz in high school... should've gone into engineering... ), as posited in the article I posted. The airplane takes off because it is pushing off against the air, not the ground.

    But on certain forums, this question has been discussed for almost 100 pages, and some people still don't get it.

    Here's another illustration that's even easier for other members to understand.

    Put a remote controlled car on a sheet of manila paper.

    Drive it forward. It pushes the sheet backward. Why? It's wheel driven. If you put it on a conveyor that matches its speed, it will stay in the same place.

    Now put a toy car of the same size on the paper, with a sail stuck in it.

    Blow on the sail with a hair dryer, careful not to blow on the paper. The car will drive off the paper without moving it. Why? It's driven by an engine acting on the air... JUST LIKE AN AIRPLANE. It does not exert force on the paper, and the paper, likewise, does not exert force on it.

    If that wind-powered car (wind-powered, just like a propeller airplane, except that the engine is not on the car, in this case) were on a conveyor belt that tried to match its speed, it would drive off easily. So would an airplane, which would reach take-off speed relative to the ground in nearly the same distance as a plane that isn't on a ridiculously long conveyor belt.

    Ang pagbalik ng comeback...

  8. Join Date
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    1,310
    #118
    Quote Originally Posted by mbeige View Post
    Pare, that was the premise. If the original premise was wrong to start with, then my answer is right. Why? Because I am basing it on the premise, while yours is wrong, because you said imposible yon. While it may be true na imposible yon, that was the original premise, and that's what we should follow in order to answer the question properly.

    Like I replied on one of the pages, "read the original question" and let's get back on topic. The premise is that the plane should lift off the ground to be considered flying, correct?

    From there I will leave it up to you guys who have more patience than me, because frankly, I think that this question is like the chicken and egg thing. Either way has a good point but both have an error.

    1. The error in my arguement is that it does not take into account that the plane's engine pushes against the air. There is another idea beside this, that the air that goes across the wings should not come from the engine, but rather from the environment. The reason I did not include this is because there was no mention of it. I am focusing on the lift, not on the forward movement, because the question is if the plane will fly or not, and the key point for the plane to fly is the Bernoulli principle, which should generate lift when the plane moves forward. But it remains stationary.

    2. On the other hand, the error in your arguement is you are negating flight. You are focusing on the forward movement, not on the lift. You cannot just forget that the plane has to fly, because that is the question. If you are basing it on forward movement, then you are not answering the question.

    However, the original premise still remains, that whatever speed the plane acquires forward, the conveyor belt matches it so that it runs at an equal but opposite direction.

    *Lolo pepe, the VTOL is different. The wings are now located at the large rotors, which move because they have axial rotation. The plane, on the other hand, has to move forward, which is the basic arguement of this thread. Because once it moves forward, it will generate lift if the speed is sufficient.

    *Niky regarding table cloth pulling: did you mean that the plate will not move, and hence, since the plane rests on the plate, therefore the plane will NOT move?

    The reason we're all having this arguement is because we're talking of two different points of views! One point of view is focused on the lift, while the other is whether or not the plane will move forward.

    1. If I focus on the lift, I will not consider the engine thrust because the premise of the original question is that the conveyor belt will match the speed in the opposite direction. This means, whatever speed the plane acquires, the conveyor belt matches it, be it impossible or not. Therefore this keep the plane STATIONARY.

    2. If I focus on the forward movement of the plane, the engine thrust has to be taken into account and this will provide the external force for the plane to move forward, and therefore, FLY.

    End of discussion!
    Hindi pa to tapos!

    The question is a chicken and egg thing if and only if we assume that the treadmill (runway) running at the same speed as the airplane creates enough FORCE as the engine thrust. None so far have explained how the conveyor belt could manage to magically create enough opposing force to counter the engine thrust. However it's entirely possible for the plane and the runway to move independently in parallel to each other due to the wheel bearings.

    Newtons third law:

    The engine thrust acting on the plane, causing it to move forward. This pushes on the wheelbearings creating a torque that causes the wheels to rotate "forward".

    The runway pulls back on the wheels, also causing it to spin "forward".

    Whatever energy the runway hands out mostly goes to spinning the wheels. A negligible amount, created by wheel bearing friction goes to pushing the plane backward. The runway would have to run much, much, much (say 10000x) faster than the plane to be able to create enough friction on the wheelbearings to push the plane backward. Which isn't quite the case here.

    mbeige: You're diverting the topic by saying rubbish like "if we focus on lift/forward movement". Of course we focus on the forward movement! If we get enough wind across the wings, it'll take care of the rest! The flying part is trivial, don't introduce more red herrings into the argument. It's the forward motion that we're concerned about here.

    The error in your argument is that you seem to conclude that the plane will stop because the conveyor matches it's speed. The runway changing its position (same rate as plane, opposite direction) does NOT imply that it counteracts the force the engine thrust creates! Why don't we go to a relatively deserted mall one 10AM and I'll demonstrate to you how I can easily match the speed of an escalator going backwards on it!

    Again: Force is not speed! Speed is not force!

    Re tablecloth pulling: What niky is saying is that the tablecloth example illustrates that if there isn't enough friction across two objects, the movement of one isn't going to appreciably affect the other. Partida to, kasi yung mga plato ni walang forward thrust - di naman sila gumalaw diba? Walang na-counteract na force. There simply wasn't any interaction between the plates and the cloth. If the plates DID have an external force pushing it forward at the moment the tablecloth is pulled, it'll move forward. You can try it with matchbox cars.
    Last edited by Alpha_One; November 10th, 2006 at 04:49 PM.

  9. Join Date
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    #119
    Quote Originally Posted by Alpha_One View Post
    mbeige: You're diverting the topic by saying rubbish like "if we focus on lift/forward movement". Of course we focus on the forward movement! If we get enough wind across the wings, it'll take care of the rest! The flying part is trivial, don't introduce more red herrings into the argument. It's the forward motion that we're concerned about here.

    Re tablecloth pulling: What niky is saying is that the tablecloth example illustrates that if there isn't enough friction across two objects, the movement of one isn't going to appreciably affect the other. Partida to, kasi yung mga plato ni walang forward thrust - di naman sila gumalaw diba? Walang na-counteract na force. There simply wasn't any interaction between the plates and the cloth. If the plates DID have an external force pushing it forward at the moment the tablecloth is pulled, it'll move forward. You can try it with matchbox cars.
    Are you accusing me of trying to divert this thread? Eh bakit, paulit ulit naman na eh. All I'm doing is giving both sides a point, but the thing is it's a matter of perspective. The flying part is mandatory, not trivial. Ano ba yan, sabi na nga ng original question is whether it will fly or not, so definitely consider the flying part! What the hell are you talking about it being trivial? Like I said earlier, in my point of view, YOU are the ones introducing the red herring by putting in the thrust where it isn't considered in the original question.

    MY point of view is that if the plane were on a normal runway, moving forward NOT by thrust (as it wasn't indicated, to reiterate), then the plane would take off because of forward movement and airspeed across the wings. However, like I said, if there was no thrust but the runway was going the opposite direction, it will negate the plane's forward motion and keep it stationary, or at least slow it down enough so it won't fly.

    Kaya nga ito nagkakagulo dahil one side is introducing an external force, while the other side is not. Hindi matatapos ang usapan nyan! I accept your arguement with respect to thrust, sana you also see our arguement where thrust is not considered and the plane can remain stationary that way. Both sides are correct and wrong at the same time. Correct in their own perspective, but wrong in the other side's perspective.

    Lastly, let's pretend you didn't say that I'm talking "rubbish" because if you ask me, yes that comes as offensive.

  10. Join Date
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    #120
    Quote Originally Posted by Alpha_One View Post
    The error in your argument is that you seem to conclude that the plane will stop because the conveyor matches it's speed.
    That was the initial premise, there is no error there.

    The runway changing its position (same rate as plane, opposite direction) does NOT imply that it counteracts the force the engine thrust creates!
    Like I said, my perspective does not include thrust.

    Why don't we go to a relatively deserted mall one 10AM and I'll demonstrate to you how I can easily match the speed of an escalator going backwards on it!
    No thanks, I'm not paying hard earned money just to fly back there for this little demonstration. Like I said, I have already accepted your side because it's a matter of perspective. It's your turn to accept my side, because both sides (as demonstrated by numerous members siding with one or the other) can happen, because it's a matter of perspective.

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