plane on a conveyor belt?

[APDrone]

Originally posted by lukster
As an object approaches the speed of light it's mass approaches infinity. Don't confuse mass with size (volume) though. Black holes can be relatively small in size but very massive.

D'oh!  Ok..  But mass does equate to weight, right?.. so if the wheel attains more mass, then the airplane engine has more mass to move, reducing it's acceleration.

I know I'm going somewhere I don't belong.

Simple vectors I can handle.. Relativity, however, is one of those relatives I'd rather not pick.

Or was it their nose?...

[vorticon]

i'm not entirely sure how hitech missed this angle in one of his first posts, and 300+ posts later, im the first to catch it:

the impossible is irrelevent to physics.

hitech says the physics equations require infinity or zero to work.

as long as the thrust is sufficiently greater than the friction between rotationless wheels and whatever the conveyer is made of, to result in the required takeoff speed, then the plane will most definatly fly.

the infinity solution is impossible.

so the only possible answer is that the plane will take off.

[lukster]

Originally posted by Terror
I did not mean to say the mass determines the actual speed, but it determines the rate at which the belt will accelerate.  (also, the diameter of the wheel also...)

Limitations of any of the physical parts are not a part of the discussion.  You have to assume the parts (conveyor, plane, engine, wheels, controller) are of limitless capabilities and will not fail under any circumstance.  Energies are tranferred, but the energies cannot cause failures within the systems they are being transfered to/through.  Otherwise you can only speculate as to which system or part will fail first.  

I think eskimo2 may have converted me.  As long as energy can be tranferred from the conveyor to wheel to the plane, then there is the possibility that the plane would sit still on conveyor.  As long as thrust is input via the engine, the conveyor would accelerate at a rate to completely counter the input energy.

The question remains in my head as to whether the above situation matches the original "the controller monitors plane's wheel speed and tunes the speed of the conveyor to be exactly the same but in the opposite direction" would allow for the belt to accelerate at a rate high enough to impart enough counter force....

Terror

We're in agreement except the part about mass of the wheel influencing the acceleration of the belt. We decide what the acceleration is to be and apply whatever force necessary to achieve it.



Maybe I'm misunderstanding you. Perhaps you are saying that a lesser acceleration will be required to hold the plane in place for a wheel with more mass?

[lukster]

Originally posted by APDrone
D'oh!  Ok..  But mass does equate to weight, right?.. so if the wheel attains more mass, then the airplane engine has more mass to move, reducing it's acceleration.

I know I'm going somewhere I don't belong.

Simple vectors I can handle.. Relativity, however, is one of those relatives I'd rather not pick.

Or was it their nose?...

Well, an object that has 1 kilogram of mass on the surface of the earth will also weigh 1 kilogram but the same object will "weigh" less on the moon but still have a mass of 1 kilogram.

[Gunston]

I can’t believe this is still going on.
There have been several similar examples like this but here is another. The plane moves because of the thrust generated by the engine (prop, jet) not the wheels so in my example we remove the engine. Ok you have your conveyor runway set up, your plane on the runway and a truck at the far end of the runway with a rope tied to the front of the plane to provide thrust. The truck starts rolling gaining speed the conveyor runs in the opposite direction matching wheel speed as you pull the plane the truck reaches 60 mph guess what the plane is going to lift off. On the next run you use the engine instead of the truck and rope for thrust the same thing will happen it will lift off.

[APDrone]

Originally posted by lukster
Well, an object that has 1 kilogram of mass on the surface of the earth will also weigh 1 kilogram but the same object will "weigh" less on the moon but still have a mass of 1 kilogram.

Ok.. so if the 1KG wheel becomes 50KG .. or 500KG.. or 5000KG as it gets closer to the speed of light, that would impact the acceleration of the Aircraft, especially since the rest of the plane is still sitting at a speed of 0.

The conveyor belt would be a headache.

I guess it would gain mass, gain weight, create a sink-hole, suck in the airplane and you'd still have no flight... lol

[Terror]

Originally posted by lukster
Maybe I'm misunderstanding you. Perhaps you are saying that a lesser acceleration will be required to hold the plane in place for a wheel with more mass?

Yes, A wheel with more mass would require a slower rate of acceleration to counter the amount of energy being applied to move the aircraft.  A wheel with less mass would require a higher rate of acceleration to counter the energy.

Terror

[Terror]

Originally posted by Gunston
I can’t believe this is still going on.
There have been several similar examples like this but here is another. The plane moves because of the thrust generated by the engine (prop, jet) not the wheels so in my example we remove the engine. Ok you have your conveyor runway set up, your plane on the runway and a truck at the far end of the runway with a rope tied to the front of the plane to provide thrust. The truck starts rolling gaining speed the conveyor runs in the opposite direction matching wheel speed as you pull the plane the truck reaches 60 mph guess what the plane is going to lift off. On the next run you use the engine instead of the truck and rope for thrust the same thing will happen it will lift off.

However the energy is added to the aircraft (engine, rope, etc), an equal and opposite reaction will occur.  The belt will accellerate the wheel at such a rate to completely "nullify" the input energy.  It is the ONLY way for the X=-X equation to balalce.  X=wheel speed, -X=conveyor speed.  (ie.  converyor moves at exact opposite speed of the wheel)  The energy applied to the aircraft is "absorbed" by the inertial forces of the conveyor accelerating the wheel at extremely high rates.  If you continue to add energy (ie. pulling the aircraft with the truck) the belt will continue to accelerate at a rate the nullifies the input energy.

The rate of acceleration of the belt depends on several factors:

1. the rate of energy being added (engine thrust, rope from truck, etc)
2. the radius of the wheel from axle to contact patch
3. the mass of the wheel and where the mass resides within the radius.

Of course, this is a philisophical/theoretical discussion.  There is no way to simulate/experiment this kind of setup.  The "perfect" systems do not exist.  A conveyor that has an unlimited acceleration capability, a wheel that has a perfect friction (slipless) contact with a surface, a wheel that can spin at an unlimited rate, etc, etc.  Real world systems would disintegrate rather quickly....

[edit for run-on sentence...]

Terror

Ps.  eskimo2,   Am i explaining things anywhere close to correctly?

[lukster]

Terror has taken the hand off and is running with ball! I'm headin' for the showers.

[SteveBailey]

However the energy is added to the aircraft (engine, rope, etc), an equal and opposite reaction will occur. The belt will accellerate the wheel at such a rate to completely "nullify" the input energy

If the truck is not on the conveyer, the airplane will move forward and take off.

The original poster didn't say anything about energy, only about wheel speed.  The conveyer would match the speed of the wheels, so say... doubling it.  the friction and rolling resistance of the wheels is miniscule compared the to thrust of the motor, doubling this incredibly small resistance would not significantly affect the takeoff speed of the plane.

Again:  The original poster did not say the conveyer was matching the planes energy, only wheel speed.  One has nothing to do with the other.

[eskimo2]

Originally posted by Terror
However the energy is added to the aircraft (engine, rope, etc), an equal and opposite reaction will occur.  The belt will accellerate the wheel at such a rate to completely "nullify" the input energy.  It is the ONLY way for the X=-X equation to balalce.  X=wheel speed, -X=conveyor speed.  (ie.  converyor moves at exact opposite speed of the wheel)  The energy applied to the aircraft is "absorbed" by the inertial forces of the conveyor accelerating the wheel at extremely high rates.  If you continue to add energy (ie. pulling the aircraft with the truck) the belt will continue to accelerate at a rate the nullifies the input energy.

The rate of acceleration of the belt depends on several factors:

1. the rate of energy being added (engine thrust, rope from truck, etc)
2. the radius of the wheel from axle to contact patch
3. the mass of the wheel and where the mass resides within the radius.

Of course, this is a philisophical/theoretical discussion.  There is no way to simulate/experiment this kind of setup.  The "perfect" systems do not exist.  A conveyor that has an unlimited acceleration capability, a wheel that has a perfect friction (slipless) contact with a surface, a wheel that can spin at an unlimited rate, etc, etc.  Real world systems would disintegrate rather quickly....

[edit for run-on sentence...]

Terror

Ps.  eskimo2,   Am i explaining things anywhere close to correctly?

Yea, you got it.

I recommend everyone watch these videos, watch the difference between a ring/hollow cylinder and a sphere.  A sphere will only have 40% of the rotational inertia of a thin walled ring.  The ring in this example has its mass near the outside, but not quite do to the traction rubber bands.  In this case the sphere probably has 50% the acceleration as the ring (because the sphere has much of its mass near the center of rotation.  These movies are much better than the wheel on the sander and have shutter speeds of 1/1000 second.

Originally posted by eskimo2


Here is a paper treadmill; the source off acceleration is a falling shoe tied to the paper.  On the paper treadmill are a mouse ball, a copper pipe with a rubber band glued around it for traction, and an acrylic ball that may have skid/slip some.

AVI:
http://hallbuzz.com/movies/paper_treadmill.AVI

QuickTime
http://hallbuzz.com/movies/paper_treadmill.MOV

[Terror]

Originally posted by SteveBailey
If the truck is not on the conveyer, the airplane will move forward and take off.

The original poster didn't say anything about energy, only about wheel speed.  The conveyer would match the speed of the wheels, so say... doubling it.  the friction and rolling resistance of the wheels is miniscule compared the to thrust of the motor, doubling this incredibly small resistance would not significantly affect the takeoff speed of the plane.

Again:  The original poster did not say the conveyer was matching the planes energy, only wheel speed.  One has nothing to do with the other.

Actually, it takes energy to accelerate the plane.  Which would spin the wheels, which would make the conveyor spin to match the wheels, which also accelerates the wheels, which adds energy in the opposite direction.  To match the wheels speed, the conveyor will continue to accelerate at an extreme rate to match the energy input from the engine.  It is the only way the conveyor can match the wheel speed.  

If the wheel rolls forward 36in in 1 revolution, and the belt moves backward 36in to "match the speed" of the wheel for each revolution, how far does the wheel/airplane move forward over the ground(or the air)?

Terror

[SteveBailey]

Originally posted by Terror
Actually, it takes energy to accelerate the plane.  Which would spin the wheels, which would make the conveyor spin to match the wheels, which also accelerates the wheels, which adds energy in the opposite direction.  To match the wheels speed, the conveyor will continue to accelerate at an extreme rate to match the energy input from the engine.  It is the only way the conveyor can match the wheel speed.  

If the wheel rolls forward 36in in 1 revolution, and the belt moves backward 36in to "match the speed" of the wheel for each revolution, how far does the wheel/airplane move forward over the ground(or the air)?

Terror

Who said it didn't take energy to accelerate the plane?
I do not know what you mean by accelerating at an extreme rate.  If the airplane accelerates to say 80 MPH, the conveyer  would be moving at  80 MPH, the wheels at 160. As I've  said, the energy parasited by the drag of the wheel is minuscule compared to the thrust of the engine.
For instance: put a beltsander upside down in a vice and turn it on.  Take your average matchbox car and set it on the belt sander without letting go. Push the matchbox against the movement of the beltsander.  Although the wheels will be spinning at the rate the belt sander(conveyer) is moving + the speed your hand is moving forward, it is quite easy to move the car along the surface of the belt sander (conveyer).

To answer your question: the wheel covers 36"  of distance in one revolution regardless of how fast it is spinning since the circumference of the wheel is 36".  So the answer to your question is that it depends on how fast the plane is moving.

[Kuhn]

Originally posted by rabbidrabbit
A plane is standing on a runway that can move like a giant conveyor belt. The plane applies full forward power and attempts to take off. This conveyor has a control system that tracks the plane's wheel speed and tunes the speed of the conveyor to be exactly the same but in the opposite direction, similar to a treadmill.

The question is:

Will the plane take off or not?

Answer: YES it will.

[SteveBailey]

At this point, anyone who still thinks the plane will not fly should either take Physics 101 or maybe ground school, although if they are still convinced the plane will not fly I doubt they are teachable/ willing to learn.