Results 111 to 120 of 154
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November 10th, 2006 02:15 PM #111
o eto na, para matigil ang discussion! film evidence!! :bwahaha:
:plane:
:threadmil
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November 10th, 2006 02:28 PM #112
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November 10th, 2006 02:29 PM #113
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November 10th, 2006 02:30 PM #114
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November 10th, 2006 02:33 PM #115
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November 10th, 2006 03:29 PM #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)
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November 10th, 2006 04:30 PM #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...
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November 10th, 2006 04:40 PM #118
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.
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November 10th, 2006 04:59 PM #119
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.
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November 10th, 2006 05:03 PM #120
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!
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!
Be careful with channels like "China Observer" on YouTube. There is a clear bias in their posts and...
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