Can Plane Take Off

SalaciousTunare said:

Heh you are all wrong.

The lift is produced by airflow over the wings, nothing else, not the prop, not the afterburner, the AIRFLOW over the wings. This explains why there are catapults on aircraft carriers, why the wind speeds are a factor in liftoff, the airflow over the wings is the only factor in takeoff. A prop, an afterburner, and a catpult are all methods of thrust to achieve the necessary airflow over the wings.

Take airplane X, chop off its wings, its max land speed is 250mph lets say.

If the conveyor belt Y can match the 250 speed, the plane will never take off. The wheels will spin at 500 mph assuming they do not fail, and the wings will have zero airflow over them, generating no lift whatsoever for the plane to achieve flight.

The plane MUST get airflow over the wings to liftoff, the prop doesn"t create vertical lift, it creates horizontal THRUST, likewise the afterburner creates horizontal thrust.

Research on the web about how wings works, how flaps work, etc.

The point about windspeed gave up the answer, when there is a tailwind you have to move faster down the runway to lift off, and when there is a headwind it takes less speed down the runway to create the necessary airflow over the wings for lift.

You could put said plane in a windtunnel, and attach it"s nose to a tether, and it would generate lift while motionless, it is the high pressure under the wing that generates the lift. Wings are curved to allow air to pass over the top of them faster generating lower pressure over the top of the wing, and higher pressure by the slower air under the bottom of the wing, that is how lift is generated.

It is the airflow over the wings that creates liftoff.

If the conveyor belt could match the full throttle speed of the plane, and have the plane essentially sitting still in relation to the tower, only spinning it"s wheels against the conveyor at max throttle not moving down the conveyor due to a lack of more horsepower, then the plane would not have sufficient airflow over the wings to generate lift.

The plane would sit there.

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if you read the other 15 pages of this thread and still came to that conclusion, as Louis Black says, "I"d like you to wear tin foil on your head so we know who you are".

Eomer said:

Man you"re an idiot.
Show me a fucking airplane that gets it"s acceleration and speed by spinning it"s goddamn wheels, you moron.

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I find this funny. The guy that"s wrong is calling the guy that"s right a moron.

The wheels don"t propel the plane. Salacious didn"t say that they do, I didn"t say that they do... What the wheels on an plane DO, in fact in the real world is prop the plane off the ground, and provide as low of a frictional impediment to acceleration as is practical.

The Wand states in his question that the conveyor not only counteracts the thrust of the plane, but even says that "However fast the plane moves, the conveyor moves just as fast." How can you interpret this to mean anything other than it"s going to keep the plane in place? TheWand didn"t say, "in the real world" or "would it be physically possible", he asked the question as it is stated in the first post, and as it was copied by me. Under the conditions he outlines he is simply saying, on an airplane that is kept from accelerating through the air (because ground speed only matters until it gains lift) will it take off.

In a normal situation, the thrust pushes the plane forward and the plane rolls on the wheels. The wheels are simply reacting to the force of the engines on the air behind the plane. It is the same as if you were standing behind the plane and pushing it. The physical mechanics are literally exactly the same. Pushing a plane with an engine or pushing it with a person, or another vehicle... all the same. As long as the external force of being pushed by another thing is related on the moving surface of the conveyor, you"ll get the same behavior.

Suppose you take the engine out of it.
Here"s this airframe sitting on a big ass conveyor and some really strong dude, like Superman is standing behind the plane (on the conveyor belt) and some other really fast guy (the flash for consistency) is adjusting the speed of this conveyor to match whatever speed the guy pushing the plane can muster. I"m not saying the belt is reacting to him pushing, I"m saying it"s counteracting his motion. In this case, the plane doesn"t take off. You can agree to that? Good.

It"s the same with the engine in the plane providing the thrust. Ground speed doesn"t "matter" except that it is a determination of how fast the plan is moving through the air (there is air around the plane and its wings), when the plane is sitting on the wheels, on the ground. It does"t matter at this point how much friction the belt produces or how much force is being applied to the wheels, it"s about whether or not the conveyor can go as fast as the jet can, in the opposite direction to the plane"s thrust. The question states that it can do that! I guess that"s what I"m asking you, Eomer, and consequentially TheWand... are you saying the question isn"t meant that way? If not, then the question needs to be changed. If you can counteract the forward motion of the plane with the conveyor, then it"s the same as if you nailed the plane in place.

(this could actually be shown IRL)
Let"s pretend we have a model plane. We attach a very fast processor computer to a laser camera and set it so that it controls the speed of a treadmill that the plane is sitting on. As the plane produces thrust, the computer adjusts the speed of the treadmill to counteract that thrust, so, in effect, the plane sits still in respect to a viewer standing on the ground; Which means there"s no airflow over the wings, which means no lift, which means no taking off. NOW let"s assume that I can provide enough thrust with my arm to make the model plane take off. I"m standing on the ground, and I have the plane in my hand. As I push the plane, the conveyor belt speeds up, and reaches its maximum speed as I"m pushing the plane faster and faster. The plane continues to accelerate with my arm, reaches its take off speed and well, takes off. The difference between these two scenarios, is that you mistakenly assume the thrust of the plane happens outside the system. It doesn"t. The directional force is being applied to the plane"s mass and the plane is on a surface that can move independantly of the surounding "ground" therefore it can counteract the force produced by the engine. When I"m pushing it while standing on the ground the force generates somewhere on my mass and is applied to the mass of the plane, consequently accelerating the plane regardless of the speed of the belt. It would be the same as if I were suspending the plane in the air with my arm.

I"m being serious about this at this point, because well... just because. If you"re just fucking around, then fine. If you don"t believe me, I"ll get force diagrams together, along with equations, with supposed values to prove out my point and post them here.

Dapopeah said:

The Wand states in his question that the conveyor not only counteracts the thrust of the plane, but even says that "However fast the plane moves, the conveyor moves just as fast." How can you interpret this to mean anything other than it"s going to keep the plane in place?

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No, the full quote was:

The conveyor is set to match the speed of the airplane in the backwords direction. However fast the plane moves, the conveyor moves just as fast.

Guess what...if the plane isn"t moving, then the conveyer isn"t either, because the plane"s speed is zero.

Sure, if you reword the question such that the conveyer moves fast enough to keep the plane stationary, then the answer changes. But that"s not exactly a big surprise. Oftentimes in a puzzle if you change the inputs the outputs change.

Frankly, this is just a poorly worded trick question, designed to get people to read it the way you did, not what is actually said.

I"ll agree with the part about the question being poorly worded and possibly requiring a change.

Pretty much everything else I disagree with, and your assumptions and conclusions are just flat out wrong. They just are. I"m tired of explaining why; if after reading through this thread you"re unable to grasp why you"re wrong, that"s your own fucking problem.

Ah fuck, maybe I"ll take a quick stab again:

Let"s pretend we have a model plane. We attach a very fast processor computer to a laser camera and set it so that it controls the speed of a treadmill that the plane is sitting on. As the plane produces thrust, the computer adjusts the speed of the treadmill to counteract that thrust, so, in effect, the plane sits still in respect to a viewer standing on the ground; Which means there"s no airflow over the wings, which means no lift, which means no taking off.

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How does the conveyor apply any force to this plane, if the wheels on it are free spinning? How is any force or energy transferred to the plane to counteract it"s thrust? Stop and think about it. This is where you go wrong. I am NOT saying that the plane"s thrust is somehow outside the system. What I AM saying is that the forces acting on the plane are essentially independent of the conveyor belt, due to the free spinning wheels (this of course isn"t completely true, but the amount of friction would be negligible). You assume that just because the conveyor is moving backwards at say 100mph while the plane goes forwards at 100mph that it somehow is magically held in place. No, it"s not. The wheels spin at 200mph, the plane goes at 100mph forward and the conveyor goes 100mph backwards.

Again assuming the wheels can withstand the increased radial velocity without blowing apart.

And no, I am not fucking around. I am dead serious. You are completely wrong, completely out to lunch. There"s no two ways about it. Your conclusions are based off assumptions that are false.

Eomer said:

I
How does the conveyor apply any force to this plane, if the wheels on it are free spinning? How is any force or energy transferred to the plane to counteract it"s thrust? Stop and think about it. This is where you go wrong.

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It"s not applying force to the plane. It"s moving in the opposite direction that the plane is attempting to move. To an observer on the plane, the conveyor is moving at blinding speed, but when he looks at the ground, the ground is sitting still.

Let me ask you this way.

We were given the condition that the conveyor can move as fast as the jet can move, but it"s moving in the opposite direction the jet is trying to move.

If you have the giant conveyor, and it"s moving at 300Mph, and you drop a plane that"s suspended just a few inches above it, onto the conveyor, what happens? The plane hits the conveyor and the inertial force of the previously not moving wheels provide a great deal of friction and the plane moves backwards, with the direction of the conveyor. Can you agree to this?

Ok, so then, lets start the throttle of the plane up, it"s moving backwards with the conveyor, and apply more and more power to the plane"s engine. The thrust of the plane eventually matches the speed of the conveyor, but all that does is stop the plane moving backwards. If you continue to apply power and therefore more thrust, AND the conveyor is sped up even more, you still have a non moving plane.

The plane hits the conveyor and the inertial force of the previously not moving wheels provide a great deal of friction and the plane moves backwards, with the direction of the conveyor. Can you agree to this?

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Yes

Ok, so then, lets start the throttle of the plane up, it"s moving backwards with the conveyor, and apply more and more power to the plane"s engine. The thrust of the plane eventually matches the speed of the conveyor, but all that does is stop the plane moving backwards. If you continue to apply power and therefore more thrust, AND the conveyor is sped up even more, you still have a non moving plane.

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Wrong.

It"s been explained literally hundreds of times in this thread alone, if you"re still thinking that the plane stands still, you"re a fucking retard. You can"t be serious, can you?

acheive thrust doesn"t mean anything. The engine is providing thrust no matter what. What matters is the movement in relation to the surroundings. It"s moving like a mofo in relation to the conveyor, but not moving in relation to the ground around it. It"s not the force on the conveyor, its the fact that he plane is sitting on the conveyor and therefore it"s motion on the conveyor is relevant. IF the conveyor wasn"t moving and the plane pushes itself, it"ll gain lift, if the conveyor is moving in the direction opposite the direction of the plane"s pushing itself, it"s not going anywhere to an outside observer, but to the conveyor it has reached or exceeded the speed where it would normally take off. Since the air around the plane is relative to the outside observer, it doesn"t move.

Dude, give it up, all you are doing is digging yourself a deeper hole.

Dapopeah said:

(this could actually be shown IRL)
Let"s pretend we have a model plane. We attach a very fast processor computer to a laser camera and set it so that it controls the speed of a treadmill that the plane is sitting on. As the plane produces thrust, the computer adjusts the speed of the treadmill to counteract that thrust, so, in effect, the plane sits still in respect to a viewer standing on the ground; Which means there"s no airflow over the wings, which means no lift, which means no taking off.

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Your inability to recognize the forces in action here make the above scenario flawed. Here is why.

The prop of a plane must be sufficeint enough to overcome the amount of drag produced by the wheels. It"s already been determined that the wheels themselves provide about 40 pounds of drag. Any plane with an engine that can provide enought thrust to compensate for the 40# drag can in effect move the plane forward. (Not counting surface grade, air movement, etc..)

Adding a conveyor belt to the scenario does nothing to increase the 40# drag provided by the wheels of the plane. If the plane has enough prop-thrust to move the plane forward at 20mph, the wheels have a rotational speed of 20mph. If the conveyor belt is running at 20mph backwards, the plane is at +20mph, the wheels are at 40mph and the belt is at 20mph.

Increase the speed of the belt and all you do is increase the wheelspeed. You do nothing to reduce the thrust provided by the prop, which will maintain a steady 20mph.

This can easily be demonstrated by using a skateboar don a treadmill. If you hold onto the rails of the treadmill while standing on the skateboard, you can overcome the energy of the treadmill easily. Increase the treadmill speed to 40mph and you are still standing. Increase to 100mph and you are still standing. Get it yet? The treadmill can"t generate enough force/drag on the wheels to require more force of your behalf of holding onto the rail.

Increase that prop-thrust to a speed needed for takeoff and the lift will be achieved and the plane will fly at a positive airspeed.

NOW let"s assume that I can provide enough thrust with my arm to make the model plane take off. I"m standing on the ground, and I have the plane in my hand. As I push the plane, the conveyor belt speeds up, and reaches its maximum speed as I"m pushing the plane faster and faster. The plane continues to accelerate with my arm, reaches its take off speed and well, takes off.

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Wow, now you are really digging a deeper hole. I guess you like calling NASA, Newton and Bernelli liars. What? Haven"t heard of Bernelli"s theory? Lemme give ya the low down ..

When a gas flows over an object, or when an object moves through a gas, the molecules of the gas are free to move about the object; they are not closely bound to one another as in a solid. Because the molecules move, there is a velocity associated with the gas. Within the gas, the velocity can have very different values at different places near the object. Bernoulli"s equation, which was named for Daniel Bernoulli, relates the pressure in a gas to the local velocity; so as the velocity changes around the object, the pressure changes as well. Adding up (integrating) the pressure variation times the area around the entire body determines the aerodynamic force on the body. The lift is the component of the aerodynamic force which is perpendicular to the original flow direction of the gas. The drag is the component of the aerodynamic force which is parallel to the original flow direction of the gas. Now adding up the velocity variation around the object instead of the pressure variation also determines the aerodynamic force. The integrated velocity variation around the object produces a net turning of the gas flow. From Newton"s third law of motion, a turning action of the flow will result in a re-action (aerodynamic force) on the object. So both "Bernoulli" and "Newton" are correct. Integrating the effects of either the pressure or the velocity determines the aerodynamic force on an object. We can use equations developed by each of them to determine the magnitude and direction of the aerodynamic force.

Simply put, that planes taking off regardless of how fast that belt can turn. Period.

This shit"s been hashed out for several years now, ever since I was in college playing around with propellants and sliding vehicles on tracks.

Here, Google is your friend, this plane definately takes off ...

http://forum.physorg.com/index.php?s...ic=2417&st=420

http://www.physicsforums.com/showthread.php?t=101259

but as long as the surface under the plane can match theforce"saffect on the body of the plane

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The conveyor is set to match thespeedof the airplane in the backwords direction. However fast the plane moves, the conveyor moves just as fast.

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There is a big difference between force and speed. You can go ahead and draw up the force diagrams if you want, but make sure you understand the question correctly first.

Jesus fucking christ. Just end it already.

Dapopeah said:

If I actually work out the equations and map it, are you educated enough to read it? I can prove this scientifically and mathmatically. I"m dead serious.

You agree that the plane, if dropped onthe conveyor would move backwards, you agree that the plane can accelerate on the conveyor, yet you disagree that the conveyor can speed up any more. OK, if it can"t speed up anymore, and the thrust can overcome the backwards motion, then yes, it can take off, but as long as the surface under the plane can match the force"s affect on the body of the plane, it"s not going to move through the air to create lift.

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Wrong wrong wrong wrong. Quit bullshitting us with your crap.

It is not wise to tip the vessel of knowledge.
Ed Grubberman, you fail to grasp Ti Kwan Leep, aproach me so that you may see ...

BOOT TO THE HEAD !

Dapopeah said:

If I actually work out the equations and map it, are you educated enough to read it? I can prove this scientifically and mathmatically. I"m dead serious.

You agree that the plane, if dropped onthe conveyor would move backwards, you agree that the plane can accelerate on the conveyor, yet you disagree that the conveyor can speed up any more. OK, if it can"t speed up anymore, and the thrust can overcome the backwards motion, then yes, it can take off, but as long as the surface under the plane can match the force"s affect on the body of the plane, it"s not going to move through the air to create lift.

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I have to agree with you, when the rest of these people explain their theory i feel like they are explaining it as if the plane has no "weight" or that it"s magically floating on the treadmill which "doesn"t matter". the mass of the plane should keep it tightly situated on the treadmill so that good contact between the wheel and the treadmill is maintained, and as long as it is, no relative motion is observed and the plane cannot "move" and thus generate any lift. i don"t get this explanation that states it"s just going to magically "pop" off the treadmill and fly away... the plane MUST roll on its wheels UNTIL it"s relative motion is fast enough that lift can be generated, at which point the wheels are no longer necessary. as long as we can pefectly counter the wheels the plane will never reach this point.

edit:

the only way i can see this plane taking off is if the treadmill/wheel contact fails. and i definitely agree that in "real life" there is no such machine or material that could "beat" the thrust of a large plane. the plane would take off after the treadmill fails and it slips off, but this isn"t real life... again, i also think the wording needs to be more specific.

bcware said:

I have to agree with you, when the rest of these people explain their theory i feel like they are explaining it as if the plane has no "weight" or that it"s magically floating on the treadmill which "doesn"t matter". the mass of the plane should keep it tightly situated on the treadmill so that good contact between the wheel and the treadmill is maintained, and as long as it is, no relative motion is observed and the plane cannot "move" and thus generate any lift. i don"t get this explanation that states it"s just going to magically "pop" off the treadmill and fly away... the plane MUST roll on its wheels UNTIL it"s relative motion is fast enough that lift can be generated, at which point the wheels are no longer necessary. as long as we can pefectly counter the wheels the plane will never reach this point.

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Off base here amigo. Some of us DO recognize the mass of the plane. The plane connects to the ground via it"s wheels. the wheels are not a device to generate thrust or power, but to reduce the intended friction of the plane in relation to the ground. An average planes wheels generate 40 pounds of drag on the plane. If the plane can generate 40 pounds of thrust, the weight of the plane in relation to the surface is negated, as in 0:0 zero-to-zero ratio.

Place a skate board on the kitchen floor.
Go stand on the skateboard.
You wont move.
Apply 1 pound of thrust (via foot) and you will move.
If you weigh 200 pounds it still only takes 1 pound of thrust.
If you weigh 100 pounds it still take only 1 pound of thrust.

Get it yet sherlocks? Once the thrust overcomes the drag produced by the wheels the ratio is NEGATED and motion (forward speed) is achieved.

Now the plane does not get it"s thrust via the foot/surface interaction., It gets it from the Air/Prop interaction. Since the AIR and the SURFACE have ZERO realtionship, the conveyor belt is a ZERO FACTOR once the drag of the wheels is overcome.

Jesus fucking christ, it doesn"t take a rocket scientist to figure the BASICS.

Let the shit die, it"s been proven OVER and OVER inthe physics community that the plane takes off. It"s been PROVEN in THJEORY and in PRINCIPLE.

Go follow those google links and post there. That way all the losers will be in one spot.

Guys, for the plane to be held in place by the conveyor, the conveyor must impart some force onto the plane.

All the other bullshit aside, how does the conveyor impart a force on the plane if said plane has freely rotating wheels? This is the core of your misunderstanding, stop and think about it very hard for a few minutes.

Hmmm .... 5 minutes of silence since the last post.

Let"s keep it that way, or I"m gonna come back and unleash the full power of Ti Kwan Leap.

trust me, you don"t want Ed Gruberman on your ass.

Yeah, work got in the way for the last hour.

Ed Gruberman can bring it. Not skeert.

All I"m saying is why don"t we have launching pads instead of runways or catapults if this shit works.

That"s all.

Because freerolling wheels are not effected by ordinary conveyor belts. You"d need to have the conveyor belt going like mach 5 to keep the plane from going forward 100mph. The friction is that off.