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

[empy]

wag mo na ubusin ang buhok mo kapatid. tignan mo ako naubos na buhok ko sakit pa rin ulo ko --> :headache:

[Alpha_One]

Let's see your FBD then.

The forces shown on the FBD are accurately depicting their directions and where they are applied.

Obviuosly, Fb, being off-center, produces torque which tends to rotate the wheel. Friction force is always against motion, if the wheel tends to move forward with Ff, then Fb will try to oppose it.

The friction on the wheel bearing is basically negligible and because of this, the wheel is allowed to rotate. When the wheel rotates, it will move forward (and the plane flies) IF the runway is not moving. With a moving runway, the forward motion of the wheel is exactly opposed, hence the wheel, although rotating, stays in place.

In the FBD, a moving runway is depicted as Fb being significant to oppose Ff. If Fb is made greater than Ff, then the wheel/plane would be moving backward! (meaning, the conveyor/runway was adjusted too fast!)

The wheel bearing, with almost zero friction, actually plays an important role of the wheel. It is its frictionless property that allows the wheel to move along the road. But with a moving runway, it is also its frictionless property that allows the wheel to stay in place while rotating.

The wheel is attached to the plane. If it moves, the plane moves. Sure you can have an FBD of the plane, and it will show the same forces. There will be Fb that will oppose Ff. There is no wind resistance when the plane is stationary or just starting to move.

Yes, its the wheel bearing that is frictionless. It does simulate a frictionless runway in the case of non-moving runway. If the runway is frictionless, the plane can take off with a ski, instead of wheels, and it would not matter if the runway is moving or not.

If the wheel bearings got stuck, the plane will not move if the runway does not move; the plane will move backwards with a moving runway (even if the engines are at full thrust).

Then let's see your FBD so you could clarify what "runway speed = plane speed" would imply.

Contrary to what you assume, if the wheel moves, the plane DOES NOT HAVE TO MOVE! You can try that with your car, jack up a non-driven wheel, let go of the brakes and spin it with your hands. Does the car move?

What frictionless property?! You can go do the matchbox-on-paper experiment to demonstrate that your assumption is completely wrong.

The wheels are attached to the plane. Yes. If the wheelbearings got stuck, all force exerted by the runway on the tires would be transferred to the plane, keeping it from moving - IF AND ONLY IF!. However, the wheelbearings serve to minimize friction EFFECTIVELY ISOLATING ANY FORCE EXERTED BY THE RUNWAY ON THE PLANE (and vice versa). VIRTUALLY NONE OF THE ENERGY exerted by the runway goes to the plane. Almost all of the energy exerted BOTH BY THE RUNWAY ON THE TIRES and THE PLANE ON THE WHEELBEARINGS go to MAKING THE WHEEL SPIN. Thus, the wheels spin faster, but the rest of the plane gets to do whatever it wants.

I'm not saying that your FBD is wrong. It's a perfectly fine representation on what's going on with the wheel. I'm saying that your ANALYSIS of the FBD is wrong. You have not demostrated any relationship between the forces acting on the wheel and any force acting on the plane, you just concluded that since the runway exerts force on the wheel it MUST exert the same force on the plane, which is completely wrong - virtually nothing happens to the plane, except the wheels spin really fast. Two linear forces act on the wheel, the engine thrust and the runway's friction on it. However, whatever torque they create causes angular velocity in the SAME DIRECTION! Meaning all the runway is doing is spin the wheel faster!

In fact, I believe your FBD is a representation of the WHEEL and the forces acting on it, which makes it irrelevant to the question.

I can't create an FBD that models runway speed = plane speed, kasi hindi naman force ang pinag-uusapan eh!!! Mahirap ba intindihin yun (apparently oo)? SPEED IS NOT FORCE, FOR THE NTH BLOODY TIME! The runway and the plane speed are NOT a function of the forces the two bodies are acting on each other! Your FBD is a red herring. So is the runway and the wheels, all of these serve as the trick to the question. The wheelbearings make whatever force the runway exerts on the plane negligible. Almost all of the energy exerted by the friction between the runway and the tires go to spinning the tires, almost NONE go to push the plane backwards.

*Kinyo: wheel speed does NOT equal airplane speed.

The airplane is not wheel driven. The wheels can be moving 1000 mph along the conveyor, and the plane will still be going at the same speed it would be going if the wheels were moving at 50.

Your analogy on the wheel plane thing is false.

If the wheel moves, the plane moves, right?

If the runway moves, does the wheel move? NO. The Wheel is not attached to the runway.

[size=4]This is the tablecloth trick. The tablecloth is the runway, the wheeled plane is a plate on the table. Pull the runway out from under the plane fast enough, and it won't move.[/size]

Now do you understand?

[nerbyoso]

i stand by my answer that the plane WILL NOT TAKE OFF.

the jet engine is just like a vacuum cleaner upfront. it sucks in air, which means all the air will go straight into the turbine and NOT PASS UNDER THE WINGS which CREATES THE LIFT necessary for the airplane to take off.

sir, sabi nga nila..."in every action there is always an opposite equal reaction"..saan naman sa tingin nyo mapupunta yung thrust generated by the jet engine? maa-absorve ng conveyor?

[boybi]

yes, it will be counter-acted by the conveyor.

[lolo pepe]

IMO, (di naman ako pilot at zero bokya ako sa physics) the airplane will fly kahit na moving in opposite direction yung runway. by the sheer power of the airplane's engines, the engines will cut/bite into the air and the plane will fly.

yung mga VTOL (vertical take-off and landing) airplanes...di nila kailangan ang runway. pwede silang mag hover a few feet above the ground and then take-off. so immaterial kung me ground contact yung wheels nila o wala, dahil so powerful yung engines nila, magkakaroon ng lift yung wings nila kaya lilipad din sila.

[nerbyoso]

yes, it will be counter-acted by the conveyor.

then again sir, i think you missed the point that much of the thrust generated by the jet engine is directed against the wind (medium) to propel it forward and not so much on the tarmac.

would you agree that a hydroplane resting on water..water being so slippery offering not much resistance and acting much like a "conveyor belt" will be able to take off? if your answer is yes, then i guess the confusion is pretty much resolved.

[mbeige]

naku! hindi pa pala tapos ito.

ok am gonna say it again..."imposible yun"...

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!

[badsekktor]

hehehe! pasakitan ng ulo dito ah! buti yun saranggola lumilipad kahit di ka tumakbo ng mabilis basta may hangin lang which i think can be dealth with propeller or jet engines... support lang talaga ang purpose ng gulong....

[rab]

:threadmil

[nerbyoso]

mbeige, you made some good arguments i must agree...hey no problem sir..this is just an exchange of opinions among guys i must pressume not involved in the aeronautics industry...its all good.

i think i already expressed enough of my opnions regarding this topic..sige kayo naman..i rest my case...cool lang kayo peeps.

[empy]

o eto na, para matigil ang discussion! film evidence!! :bwahaha:

:plane:
:threadmil

[mbeige]

o eto na, para matigil ang discussion! film evidence!! :bwahaha:

:plane:
:threadmil

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

[ozcity]

o eto na, para matigil ang discussion! film evidence!! :bwahaha:

:plane:
:threadmil

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

[ozcity]

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

[mbeige]

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!

[Helios]

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)

[niky]

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.

[Alpha_One]

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.

[mbeige]

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.

[mbeige]

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.