Will it take off?

billybob

thats funny, just looked for you there - that was the page where I said they were calling each other names! And you were one of them! Great stuff! Don't know much about physics, but I'm sure "dill hole" isn't a generally accepted term like "wormhole"

Take care man

Everyone who says that the wheels are turning twice as fast is mistaken about the "independant" thrust generated by the engine.

To say it again the plane will not take off.

Here is why

Take your converyor and run it at lets say 10ms going to the right (backwards) hold a model plane a car whatever in your hand over the conveyor, now bring it into contact with the conveyor.

The wheels of the plane car etc are turning at 10ms, while you are standing still and holding it over the conveyor.

Now lets say you move the car plane etc forward over the moving conveyor at a rate of 1ms, the wheels therefore are traveling at 11ms and the car/plane etc has moved forward in position (1ms in distance) in regards to its postion from point A to point B.

So by using this scenario you are saying just like a jet engine, independant of the conveyor motion and the rate of the car/plane adds on top of the conveyor rate of motion to get increase of the wheel speed to the point that when the car/plane is moving at the same rate that the wheel speed should be double of the conveyor speed and that the car/plane would be moving forward at the rate of 10ms.

Sounds like this is what you are saying.

BUT the only problem is that by standing next to the conveyor and holding onto the car/plane etc that you are then countering the positional movement of the converyor since YOU are not standing on the conveyor moving along with it, YOU become an equallizing force to the movement of the car/plane etc on the conveyor. So you become a third force which equalizes the force movement of the conveyor allowing the force/movement of the planes engine to then overcome the positional movement of the conveyor. Thus allowing the wheel speed to become increased above the conveyor speed.

BUT in our question the conveyor in fact does not move at a set rate.

So again using the above example standing next to a moving conveyor holding a wheeled, skidded or anyother object over the conveyor then coming in contact with it at say 10ms, you attempt to move the car/plane etc forward at 1ms, the conveyor sensing the increase in velocity of the object over the conveyor equally speeds up to 11ms, thereby increasing the force requried to move the car/plane etc to something higher then 11ms so you apply more force to swing the car/plane etc forward on the conveyor only to have the conveyor equal the force and speed up.

The more force you apply to try and move it forward the more force the conveyor applys in the opposite direction to push it back.

At 20ms you would need to push with 21ms of force to move 1ms at which time the conveyor would then equalize and move at 21ms in the opposite direction. It would become increasingly harder to push forward to move that additional 1ms.

Since there is nothing about the limit to the amount of force either the plane nor the conveyor can generate then it would come down to which failed first. As being the ultimate solution to if the plane would take off or not.

If the plane is trying to push forward with 10,000 force units and the conveyor is pushing back with the equivalent of 10,000 force units then the plane has to make 10,001 just to move forward. It would not move exponetially faster forward since it is alright moving against the equal to 10,000 force units, it would merely travel along the length of the conveyor at the rate of 1ms until it reached the end at which point given the space available it would then start to accelerate at what ever the thrust to weight ratio /mass allowed it to accelerate at. And given enough space remaining would take off like normal.

You could conceivable build a test model by using an electrical torque sensor an arm attached to some sort of car or plane model and moving belt surface that had a speed govenor that you could like to the torque sensor.

As you apply torque on the arm which is connected to the car whatever on the belt attempting to swing it over the surface of the belt as you applied torque the belt would see the new torque amount and speed up the belt to equal the amount of force you are attempting to apply to the car plane etc until both reached ad infinite and something failed.

Since we are dealing with gravity the mass of the plane on the conveyor plus the speed (velocity) at which the conveyor is attempting to the move the plane in a given direction is going to equal a certain amount of force. Since the plane is attempting to overcome this force its engine must also deal with the effects of gravity on the mass and counteract the net force of the conveyor attempting to move it back, As the plane generate more force, so does the conveyor. The wheels have nothing to do with cancelling or adding into the planes favor as the MASS of the plane still exist as is acting ON THE CONVEYOR due to gravity, thus the engine must still overcome the mass of the plane + opposite force.

To solve this question you have to solve using the same term "force" in both cases as the plane model is tricking you by using terminology such as ground speed vs airspeed.

The plane requires X airspeed,

Under normal conditions, therefore the plane must travel forward at a groundspeed of Y

The plane produces Z amount of thrust and the plane weighs A amount in lbs, which gives us a rate of acceleration of R.

If traveling into the wind at a rate of W it is possible for the plane to takeoff at a ground speed on Y-R

As long as Airspeed X and Windspeed R remain constant or increasing then the plane will remain in the air.

So logically speaking then if the conveyor under the plane is moving at a constant rate = to the required groundspeed of the plane to "fly" Y yet in the opposite direction then it would be assumed that the following is true

Groundspeed = Y x 2 required for flight when Ground is 1/Y

BUT in our case Y and 1/Y are always equal

Therefore without the plane moving (which is a requirement of force) at a rate higher then the equal yet opposite rate of the ground then it can not generate enough airspeed to "fly"

Originally posted by robertfenix
Everyone who says that the wheels are turning twice as fast is mistaken about the "independant" thrust generated by the engine.

To say it again the plane will not take off.

Here is why

Take your converyor and run it at lets say 10ms going to the right (backwards) hold a model plane a car whatever in your hand over the conveyor, now bring it into contact with the conveyor.

The wheels of the plane car etc are turning at 10ms, while you are standing still and holding it over the conveyor.

Now lets say you move the car plane etc forward over the moving conveyor at a rate of 1ms, the wheels therefore are traveling at 11ms and the car/plane etc has moved forward in position (1ms in distance) in regards to its postion from point A to point B.

So by using this scenario you are saying just like a jet engine, independant of the conveyor motion and the rate of the car/plane adds on top of the conveyor rate of motion to get increase of the wheel speed to the point that when the car/plane is moving at the same rate that the wheel speed should be double of the conveyor speed and that the car/plane would be moving forward at the rate of 10ms.

Sounds like this is what you are saying.

BUT the only problem is that by standing next to the conveyor and holding onto the car/plane etc that you are then countering the positional movement of the converyor since YOU are not standing on the conveyor moving along with it, YOU become an equallizing force to the movement of the car/plane etc on the conveyor. So you become a third force which equalizes the force movement of the conveyor allowing the force/movement of the planes engine to then overcome the positional movement of the conveyor. Thus allowing the wheel speed to become increased above the conveyor speed.

BUT in our question the conveyor in fact does not move at a set rate.

So again using the above example standing next to a moving conveyor holding a wheeled, skidded or anyother object over the conveyor then coming in contact with it at say 10ms, you attempt to move the car/plane etc forward at 1ms, the conveyor sensing the increase in velocity of the object over the conveyor equally speeds up to 11ms, thereby increasing the force requried to move the car/plane etc to something higher then 11ms so you apply more force to swing the car/plane etc forward on the conveyor only to have the conveyor equal the force and speed up.

The more force you apply to try and move it forward the more force the conveyor applys in the opposite direction to push it back.

At 20ms you would need to push with 21ms of force to move 1ms at which time the conveyor would then equalize and move at 21ms in the opposite direction. It would become increasingly harder to push forward to move that additional 1ms.

Since there is nothing about the limit to the amount of force either the plane nor the conveyor can generate then it would come down to which failed first. As being the ultimate solution to if the plane would take off or not.

If the plane is trying to push forward with 10,000 force units and the conveyor is pushing back with the equivalent of 10,000 force units then the plane has to make 10,001 just to move forward. It would not move exponetially faster forward since it is alright moving against the equal to 10,000 force units, it would merely travel along the length of the conveyor at the rate of 1ms until it reached the end at which point given the space available it would then start to accelerate at what ever the thrust to weight ratio /mass allowed it to accelerate at. And given enough space remaining would take off like normal.

You could conceivable build a test model by using an electrical torque sensor an arm attached to some sort of car or plane model and moving belt surface that had a speed govenor that you could like to the torque sensor.

As you apply torque on the arm which is connected to the car whatever on the belt attempting to swing it over the surface of the belt as you applied torque the belt would see the new torque amount and speed up the belt to equal the amount of force you are attempting to apply to the car plane etc until both reached ad infinite and something failed.

Since we are dealing with gravity the mass of the plane on the conveyor plus the speed (velocity) at which the conveyor is attempting to the move the plane in a given direction is going to equal a certain amount of force. Since the plane is attempting to overcome this force its engine must also deal with the effects of gravity on the mass and counteract the net force of the conveyor attempting to move it back, As the plane generate more force, so does the conveyor. The wheels have nothing to do with cancelling or adding into the planes favor as the MASS of the plane still exist as is acting ON THE CONVEYOR due to gravity, thus the engine must still overcome the mass of the plane + opposite force.

To solve this question you have to solve using the same term "force" in both cases as the plane model is tricking you by using terminology such as ground speed vs airspeed.

The plane requires X airspeed,

Under normal conditions, therefore the plane must travel forward at a groundspeed of Y

The plane produces Z amount of thrust and the plane weighs A amount in lbs, which gives us a rate of acceleration of R.

If traveling into the wind at a rate of W it is possible for the plane to takeoff at a ground speed on Y-R

As long as Airspeed X and Windspeed R remain constant or increasing then the plane will remain in the air.

So logically speaking then if the conveyor under the plane is moving at a constant rate = to the required groundspeed of the plane to "fly" Y yet in the opposite direction then it would be assumed that the following is true

Groundspeed = Y x 2 required for flight when Ground is 1/Y

BUT in our case Y and 1/Y are always equal

Therefore without the plane moving (which is a requirement of force) at a rate higher then the equal yet opposite rate of the ground then it can not generate enough airspeed to "fly"

Your hand in that car scenario is acting as thrust, not some magical third force.

This has already been discussed. In order for the belt to move AT ALL, the plane has to be physically moving through space. There are no speedometers on airplanes ... they use airspeed indicators, which are simply pressure guages. This is what would have to be measured by the conveyor belt's sensors. So the plane would have to start moving forward along the belt in order for the belt to move at all. If the plane starts moving at 1 m/s forward the belt counters at 1m/s backwards. Note that the plane's 1/ms speed is not relative to the BELT ... it's relative to the air surrounding it (note: airspeed indicators are compensated for wind so that a reading of 1m/s on the indicator has already been calibrated against windspeeds). Thus, to an outside observer, you see the plane moving forward 1m/s, and the belt will be moving in the opposite direction at 1/ms causing the wheels to spin at 2m/s.

This is where people keep getting hung up ... we think that since the plane's speed and the belt's match, the plane will not move physically through space. We fail to realize that it's the forward motion THROUGH SPACE that causes the belt to move in the first place. For the entire time the plane is overcoming the inital friction of the wheels on the belt, it is like a normal takeoff (the belt is not spinning because the plane has not moved yet).

Once you realize with your car analogy that the belt only moves AT THE SPEED WITH WHICH YOU PUSH THE CAR RELATIVE TO A POINT OUTSIDE THE SYSTEM, it's easy to see the plane will move down the runway and take off.

Originally posted by robertfenixThe more force you apply to try and move it forward the more force the conveyor applys in the opposite direction to push it back.

You had a fairly good grasp of the arguments up to that point. The mistake though, is that th wheels exist for the sole purpose of ensuring the conveyer is unable to effectively or efficiently apply it's motion as force.

Originally posted by Travellar

Originally posted by robertfenixThe more force you apply to try and move it forward the more force the conveyor applys in the opposite direction to push it back.

You had a fairly good grasp of the arguments up to that point. The mistake though, is that th wheels exist for the sole purpose of ensuring the conveyer is unable to effectively or efficiently apply it's motion as force.

Exactly. Think of a plane on the static runway. The wheels are what allow the plane to be moved down the runway via the thrust. The only force they cause on the plane is a bit of friction (and this is minimized as much as possible in aircraft to minimize the necessary thrust, and in turn, fuel consumption). It is no different on a conveyor belt ... the wheels freely spin.

Haha it's amazing how much this has turned from a physics problem into a question of semantics.

Does anyone know of any other boards where someone has proven it with like an RC plane or something? If I had the bones I'd set it up (I even have a few old treadmills/motors I could use, but no plane).

Originally posted by robertfenix
Take your converyor and run it at lets say 10ms going to the right (backwards) hold a model plane a car whatever in your hand over the conveyor, now bring it into contact with the conveyor.

Wow, the first line of the example already negates it's relevence.

The plane doesn't start out on a moving conveyer.

Here's a proper analogy.

Your speed = the "air speed" (the way a plane measures speed so that's what the conveyer matches, which is also completely independant of the conveyer)

Place the model plane on the stationary conveyer.

Now, walk next to the conveyer, and push the model plane along, at 1mps.

The conveyer begins to match your speed, underneath the model plane, in the opposite direction at 1mps.

Does this stop you or hold you in place? No

Does it hold the model plane in place? No, it's moving forward at 1mps right along with you, however, it's wheels are now freely-spinning at 2mps.

Now accelerate yourself, and the model plane, to 2mps.

Remember, you are not on the conveyer. You are independent just like the air speed that a plane measures speed by, and independent like the plane's thrust.

The conveyer now matches the model plane's speed at 2mps (in the opposite direction).

Does this stop you or, "hold the model plane in place"? No

Now the model plane is moving forward at 2mps, the conveyer matches in the opposite direction, and the combination is causing the wheels to freely-spin at a rate of 4mps (even though the model plane's speed/air speed is only 2mps).

Keep accelerating with your independent thrust and air speed(your speed):

3mps(air speed/yourspeed)+3mps(conveyer that is matching)=6mps(wheel rotation)
4+4=8
5+5=10
6+6=12
etc..........

Do you see the pattern?

The wheels are free-spinning, not speeding you up or holding you back.

You are the independent thrust.

Your speed forward is the airspeed (which is what a plane's speed is measured by).

Hopefully this (and the three posts above this ) will make it clear for ya.

[edit on 2/23/06 by redmage]

Originally posted by maldives01
billybob

thats funny, just looked for you there - that was the page where I said they were calling each other names! And you were one of them!

Great stuff! Don't know much about physics, but I'm sure "dill hole" isn't a generally accepted term like "wormhole"

Take care man

i'm beginning to wonder. i TRY to be polite, there, but there is a lot of pride and passion in BIG HEADS, it seems, lol!
also, there are NASTY disinfo agents, that feel it's there duty 'moronize' anyone who disagrees with them. (well, frankly, it IS their duty, as they are, most likely, being paid to do it.)

'dillhole', HAHAHA! that one was funny.

did you check out the 'basic physics, the proper analysis of the tower collapses' thread?

there's some real 'mass holes', there, LOL!

I get your drift bb, I don't like disinfo either - I find it dishonest and demeaning - there are other things I could say as well! BTW I find your "will it or won't it" explanations ( or arguments:lol very persuasive - I'm firmly wavering towards your camp now Keep up the good work

I don't think the plane will ever reach the 88 miles per hour necessary to trigger the flux capacitor.

the thrust of the engines would extremerly outweigh the minute rolling friction of the tyres agaist the huge treadmill.

its like getting on a treadmill with rolerblades and using a rope to pull yourself in

thinking that a treadmill of such preportions can be built is silly, that someone would build it is silly and that it could accelerate to the speeds at whcih the rolling friction of the wheels will overtake the thrust of the jet engnes is silly

plane will take off

Originally posted by veespec
the thrust of the engines would extremerly outweigh the minute rolling friction of the tyres agaist the huge treadmill.

its like getting on a treadmill with rolerblades and using a rope to pull yourself in

thinking that a treadmill of such preportions can be built is silly, that someone would build it is silly and that it could accelerate to the speeds at whcih the rolling friction of the wheels will overtake the thrust of the jet engnes is silly

plane will take off

well, MOST of us prefer PROportions to PREportions, so you are a non-person as of, wait for it, ........NOW!

you seem to have forgotten the difference of gravity between earth and the moon, and the different drag effects of a triple hull vs. a single hull boat!!!!!

have you forgotten that mass INCREASES with velocity!!!!?

so, while the plane is accelerating, it is GAINING WEIGHT, while the belt has become a function of mass over time, effectively LIGHTENING the BELT!!!!

(okay, i'm sorry. i'm making fun of some 'agent provocateur' at physorg.com. you are, of course, correct)




[edit on 9-3-2006 by billybob]

dont be dumb, the air still moves at normal speed. whatever the planes doing on the ground doesnt matter, it just has to hit the wind with a certain velocity relative to the wind.

i guess if you dont want to be logical about it, air tuneels wouldnt work otherwise.

The plane doesn't stay still. Therefore it takes off.

How hard was that?

reply to post by ShatteredSkies


well... for my first post here, i'm going to wade in... i'm going to go and sit in the yes it will camp... but i'm going to try a small scale experiment with a model aircraft and a treadmill and see what happens... i can't believe no-one else here has a $50 toy plane and a gym membership!

Originally posted by rat256
reply to post by ShatteredSkies

 

well... for my first post here, i'm going to wade in... i'm going to go and sit in the yes it will camp... but i'm going to try a small scale experiment with a model aircraft and a treadmill and see what happens... i can't believe no-one else here has a $50 toy plane and a gym membership!

try and watch the video in the post above yours(mine).

it's a link to a real life experiment with a plane and conveyor belt. it was done by 'mythbusters', the TV show. they also did a small scale expriment on an earlier show.

the plane takes off, and i can't believe this has actually been any confusion over what would happen.

i mean, even the damn pilot who takes off from the conveyor belt thought he wasn't going to take off.

this is maybe why so many people bought the 911 lie hook, line and sinker. a sickness of the mass communication/automation society.

that video wouldn't work... which is why i posted!! but i'm glad i think along the same lines as the mythbusters (that series hasn't hit the UK yet!)

Originally posted by HowardRoark

A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?"

i got to the 6th page, and decided to go ahead and post. im sorry if its been mention already.

its a trick question. neither the plane or the belt are moving. and i see no mention of an observer.

its says the plane is "standing on a runway". not rolling.

it says "the plane moves in one direction", but there was no mention of the plane beginning to move. no plane movement, no belt movement. it only explains how the belt "would work".

even if you assume the plane is moving. it would fly. better get those tires and bearings rated though

for belt to move, the plane has to move. if the plane is moving, it is moving through ambient air. the faster the plane moves, the faster the belt moves.

if you are the observer ( not sure where the observer came from, but, ill go with it) and you marked the belt just below the plane before the experiment, and then started the experiment, you would see the mark on the belt go one direction and the plane the opposite direction. (better check those tires check again before you start though.)

-----------------edit---------------
guess i should have kept reading. i see this has already been solved.

[edit on 21-2-2008 by JSR]

Neglecting the wheel speed rating, the aircraft takes off.


In the real world, the tyre speed rating will be lower than 2X the rotation speed - so the tyres will fail and the aircraft will "crash".

Originally posted by kilcoo316
Neglecting the wheel speed rating, the aircraft takes off.


In the real world, the tyre speed rating will be lower than 2X the rotation speed - so the tyres will fail and the aircraft will "crash".

doesn't anyone watch the durn video from mythbusters that i posted?

in the real world, the tired can EASILY take the double speed rotation, and the plane takes off, like it did in the real world.

[edit on 21-2-2008 by billybob]