Can an airplane on a conveyor belt take off? (resolved)

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Exnihiloest
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Re: EELV controversy on aviation and children's dreams (Mayor of Poitiers)




by Exnihiloest » 14/05/21, 21:42

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Christophe wrote:Ahmed if your crazy wheel theory was right you should be able to push a plane or a train just by touching it ... right? We must not have the same conception of the marginal ... : Cheesy: : Lol:

This is not "his" theory, it is Newton's first law! No force / energy is necessary to maintain a movement at constant speed, unless there are losses (friction, air resistance ...).
It takes an energy only to make it change speed, so if it was at rest either v = 0, to make it acquire a speed v> 0 (E = 1 / 2.m.v²), but this energy can be arbitrarily low if the final speed is arbitrarily low. So yes, touching an airplane or a train would set them in motion, as long as the friction had been eliminated, for example by sustaining them by a magnetic field rather than wheels or by assuming them to be weightless.

If your reasoning was correct then no freewheel could transmit power through a treadmill

It's the case. A wheelchair on a treadmill would stay put, if it were ideal (frictionless wheels). In practice, of course, there is always friction, the chair will be driven.

Newton's first law: no force (therefore no energy) is necessary to maintain uniform motion. An object at zero or constant speed remains like this as long as no force is exerted. In the cases we have seen, the force can only come from friction.
Are you really an engineer?
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Re: EELV controversy on aviation and children's dreams (Mayor of Poitiers)




by Christophe » 15/05/21, 01:53

blablabla ... According to Newton's 1st law no car should consume more than 0.2 / L per 100km in a frictionless world ... so excuse me for being an engineer who reasons in the real world ... and not the your physical care bears ... : Shock:

Then hold the care bears of the world without friction: lift is a phenomenon of friction it seems to me...

And so in your world of frictionless reasoning no plane would fly! And the deal should have been concluded very quickly: the plane will never take off ... : Mrgreen: : Mrgreen: and we would have agreed even if it is not for the same reasons ... case closed ...

You hadn't seen this one coming, eh, it's called a dantaface of nasty and ugly care bears pabo : Mrgreen: : Mrgreen: : Mrgreen:

In short you idealize part of the problem by forgetting the fundamental : Shock: So before shouting the absurd and the bias of others, look at yours ...

Are you really scientists? : Shock: : Shock: : Shock:
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Re: EELV controversy on aviation and children's dreams (Mayor of Poitiers)




by Ahmed » 15/05/21, 08:55

Bah! It is you who starts from the principle that the friction of the wheels on the carpet is able to transmit a considerable power likely to oppose the progress of the plane, therefore its takeoff, whereas I do not deny that a small influence can be observed, but by no means decisive ...

I am in the process of replacing a centrifugal clutch by a belt clutch on my shredder: for this I use a pressure roller which will tension the belts ... But the roller itself does not transmit any power and if it is rotary, this is to minimize the inevitable friction *, and therefore the power absorbed.

* Resistance of the ball bearing and deformation of the belts.
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Re: EELV controversy on aviation and children's dreams (Mayor of Poitiers)




by Christophe » 15/05/21, 10:32

Ahmed wrote:Bah! It is you who starts from the principle that the friction of the wheels on the carpet is able to transmit a considerable power likely to oppose the progress of the plane, therefore its takeoff, whereas I do not deny that a small influence can be observed, but by no means decisive ...


Take the problem differently then: blow a tail wind of 300 km / h on a Boeing ... will it manage to take off? Assuming that this wind does not de ... zinc! : Cheesy:
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Re: EELV controversy on aviation and children's dreams (Mayor of Poitiers)




by Ahmed » 15/05/21, 10:55

I am not walking in your scheme! 8) What do you imagine? :P
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Re: EELV controversy on aviation and children's dreams (Mayor of Poitiers)




by Christophe » 15/05/21, 11:05

Mouahahaha what bad faith !!!

Yet this is the initial statement of the effects on the aircraft, isn't it? Maybe you want me to paste it for the 3rd time?

Let us laugh here!
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Re: EELV controversy on aviation and children's dreams (Mayor of Poitiers)




by Ahmed » 15/05/21, 11:09

The statement is bogus ...
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Re: EELV controversy on aviation and children's dreams (Mayor of Poitiers)




by Christophe » 15/05/21, 11:25

Like this one ? : Cheesy: : Cheesy: : Cheesy:

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Re: EELV controversy on aviation and children's dreams (Mayor of Poitiers)




by Ahmed » 15/05/21, 11:38

... x is on a bad slope ... not even screwed to take off.
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Re: EELV controversy on aviation and children's dreams (Mayor of Poitiers)




by Christophe » 15/05/21, 12:33

Where is the conveyor belt? : Cheesy:

Good Ahmed: we will agree .... yes if yes!

I agree with the fact that an airplane (or whatever thrust on its chassis without a drive wheel) is moving on a conveyor belt ...and that it is not just necessary to counter the internal friction forces of the wheels (= f (mass, RPM))!

a) So you (I, we ..) consider thata freewheel cannot transmit power apart from internal friction ok ?

Say they represent 1% of the power of the treadmill? It doesn't matter what number: it can be 10%, 0.1% or 0.00001% ...

b) Nowhere does it say that the treadmill and the wheels had physical limitations in the statement : it is said that the conveyor belt compensates for the advancement of the plane, that's all!

It has never been said that the treadmill compensates for progress as if it were driving wheels!

The wheels can therefore turn at 1 RPM and the belt can move forward at 000 km / h ... and therefore induce sufficient internal friction to compensate for the thrust!

c) a) + b) = the plane does not move forward ... and does not take off on this "magic" carpet if it is not flying *!

So who is Exni the GOOD ENGINEER?

There is therefore only one correct answer and N reasoning to get there: the plane does not take off! I remind you that in your world without friction there is no lift possible! : Cheesy:

* in the real world everything will explode well before obviously ... and a carpet which would advance at 10 km / h would set in motion so much air with it that it would create the relative wind necessary and sufficient to make a wing take off at a few m from him !! Good STOP! My conclusion already said above is therefore still valid: in physical theory it cannot take off but in practice it takes off because of ... physical limits!
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