Airplane on a Conveyor conundrum

[dieselboy]

Explain how the speed of the conveyor *whatever it is* is able to act upon the aircraft? All the aircraft has to do is overcome the friction within the wheels. Seeing as it is able to do that in a normal takeoff, then it will have no problem doing it when sat on a conveyor that may *or may not* be changing the rotational speed of the wheels (and that is all that it can do).

the conveyor acts on the aircraft through the wheels.
doesnt matter if its on ice either. if the jets have only enough power to move the plane forward at 600mph on ice, then if the ground was going the reverse at 600mph then the plane will not move.

the only thing is, that when the real planes get up to their top speed, its because of wind resistance and not resistance through the wheels.

this wont matter in this situation because the plane only has enough power to get to a certain speed whilst on the conveyor. it can be any speed you like, and it can be on rollerskates, ice blocks or wheels.

if the maximum force of the plane is 1200mph on ice blocks, and the conveyor was going the other way at 1200mph, then the plane still would not take off.

[dieselboy]

No, police patrol cars (note, not panda cars) have calibrated speedos, that's how they know their speed. The speedo has to be calibrated regularly, if it hasn't been done properly you can use that fact to fight a speeding ticket.

yer i know that. you can request proof that its been calibrated in court of law. i thought that they may have changed that now though for a better system.

[dieselboy]

OK, look, go here:

http://www.youtube.com/results?searc...s&search_type=

Watch the top two videos.

IT ACTUALLY HAPPENED!

im at work cant do it. what is it?

[Slugsie]

the conveyor acts on the aircraft through the wheels.

But the amount of force it can apply is only equal to the friction within the wheel system.

[Slugsie]

im at work cant do it. what is it?

It is videos of the Mythbuster crew, with a plane, sat on as near to a conveyor as they can get, and watching the plane take off.

[dieselboy]

Err, so where exactly is all the thrust from the engines going? It's certainly not being directed into the conveyor, as that is not how an aircraft directs its thrust.

yer i know but the conveyor is acting a force on the plane. so the plane will have to give out the same force just to stay still. it will have to give the same force plus a bit more to accellerate

in real life this wont ever happen because there is no way of getting the two to be exactly the same 100% of the time

[Slugsie]

the conveyor acts on the aircraft through the wheels.
doesnt matter if its on ice either. if the jets have only enough power to move the plane forward at 600mph on ice, then if the ground was going the reverse at 600mph then the plane will not move.

the only thing is, that when the real planes get up to their top speed, its because of wind resistance and not resistance through the wheels.

this wont matter in this situation because the plane only has enough power to get to a certain speed whilst on the conveyor. it can be any speed you like, and it can be on rollerskates, ice blocks or wheels.

if the maximum force of the plane is 1200mph on ice blocks, and the conveyor was going the other way at 1200mph, then the plane still would not take off.

Basically, if the plane gained speed, and moved over the surface (be it ice, tarmac, conveyor, or rice pudding) in the way a car does, then you would be 100% correct. But planes don't work that way, so you are 100% wrong.

[dieselboy]

It is videos of the Mythbuster crew, with a plane, sat on as near to a conveyor as they can get, and watching the plane take off.

ill watch it when i get home.
ive seen them programs before and ive stopped watching them because a lot of times they have been wrong and ive felt like smashing the tv up.

i dont watch tv any more. but will do tonight because skins series two starts

[dieselboy]

Basically, if the plane gained speed, and moved over the surface (be it ice, tarmac, conveyor, or rice pudding) in the way a car does, then you would be 100% correct. But planes don't work that way, so you are 100% wrong.

but it doesnt matter because there is a force acting on the plane still and is counteracting its forward movement.

[Slugsie]

yer i know but the conveyor is acting a force on the plane. so the plane will have to give out the same force just to stay still. it will have to give the same force plus a bit more to accellerate

in real life this wont ever happen because there is no way of getting the two to be exactly the same 100% of the time

But the force given out to stay still will be minimal (law of physics/momentum 'a body at rest tends to stay at rest'), and only that necesary to overcome the friction of the wheels and bearings, and much much less than the maximum potential of the engines.

If you were to create perfect frictionless bearings, and tyres with no rolling resistance, then the aircraft would indeed stay still without the need of its engines if you tried to move the ground beneath it. I know that sounds a little silly, but it is the truth. A slightly different way of looking at this is the old pulling a table cloth off a table without disturbing the dishes. In this case the rapid acceleration of the cloth momentarily overcomes the friction, and the overwhelming force on the dishes is their (lack) of momentum.

[Slugsie]

but it doesnt matter because there is a force acting on the plane still and is counteracting its forward movement.

No, there isn't, not one of any significance. Not if you are working with an aircraft that is normally capable of flight.

[dieselboy]

But the force given out to stay still will be minimal (law of physics/momentum 'a body at rest tends to stay at rest'), and only that necesary to overcome the friction of the wheels and bearings, and much much less than the maximum potential of the engines.

If you were to create perfect frictionless bearings, and tyres with no rolling resistance, then the aircraft would indeed stay still without the need of its engines if you tried to move the ground beneath it. I know that sounds a little silly, but it is the truth. A slightly different way of looking at this is the old pulling a table cloth off a table without disturbing the dishes. In this case the rapid acceleration of the cloth momentarily overcomes the friction, and the overwhelming force on the dishes is their (lack) of momentum.

yes okay, but if the force coming out of the back of those engines was only enough to even make the plane go 10mph then the conveyor moving at 10mph would be enough to keep the plane stationary.

your question has no constants, and is partly why i was led to understand that the conveyor speed was relative to the plane.
that makes sense lol

[Chillitt]

[QUOTE=dieselboy;409833 the conveyor moving at 10mph would be enough to keep the plane stationary.

[/QUOTE]

Descibe/ define this force, how is it acting on the plane? The only contact it has with the plane is through the wheels, which turn freely. Also, how is this force changed by different levels of thrust from the engines acting on the air. Just tell us how exactly it affect the plane.

[Slugsie]

yes okay, but if the force coming out of the back of those engines was only enough to even make the plane go 10mph then the conveyor moving at 10mph would be enough to keep the plane stationary.

Only if the frictional drag of the wheels was sufficient to retard that 10mph force. But such a plane would never be able to take off, and one of the basic assumptions was that the plane was capable of takeoff under normal circumstances.

your question has no constants, and is partly why i was led to understand that the conveyor speed was relative to the plane.
that makes sense lol

But, it doesn't really need them. The only time you do need the constants is if you want to model exactly what happens each and every second, not what the outcome would be.

[BUSHWHACKER]

im at work cant do it. what is it?

You're gonna have to work on the week-end to make up time for today then.