Physics Puzzle

[Softus]

So the only constraint is friction? So which of us knows whether there is enough friction in the wheels to slow the plane down to the degree that is causes sufficient drag to ****** the plane's speed for take-off?

If the answer is none of us - then we may as well forget the question as it has no answer.

Unaldulterated and faultless logic from joe-90 - I agree completely.

kendor, if you're unwilling to open your mind to the problem and how to think about it, then why keep posting? I, for one, am happy to accept that you have a different answer to every mathematician and engineer on the planet.

 

[kendor]

So the only constraint is friction? So which of us knows whether there is enough friction in the wheels to slow the plane down to the degree that is causes sufficient drag to ****** the plane's speed for take-off?

If the answer is none of us - then we may as well forget the question as it has no answer.


joe

no you misunderstood me i meant the friction of the wheels attaching to the ground they have to have friction otherwise they would not spin at the same speed as the runway does although they wouldn't spin at all in that case because the runway speed is determined by the speed that the wheels are spinning at.

 

[kendor]

So the only constraint is friction? So which of us knows whether there is enough friction in the wheels to slow the plane down to the degree that is causes sufficient drag to ****** the plane's speed for take-off?

If the answer is none of us - then we may as well forget the question as it has no answer.

Unaldulterated and faultless logic from joe-90 - I agree completely.

kendor, if you're unwilling to open your mind to the problem and how to think about it, then why keep posting? I, for one, am happy to accept that you have a different answer to every mathematician and engineer on the planet.

Softus your comments are not wanted if you have no constructive criticism, if you think you know anything then explain why my argument isn't sound.
to just argue, wrongly that mathmeticians and the like disagree with me without showing any proof is one of your usual throwaway statements that personally i think deserve no more than they deserve.
I posted as i believe no-one here has as yet answered the question correctly.
Why don't you open your mind to the fact that you are an interfering no nothing idiot? I've accepted that you are and so should you by now! either that or stop posting your idiotic comments.

 

[kendor]

Now where were we?

 

[Softus]

Softus your comments are not wanted

Yes they are - they're wanted by me.

if you have no constructive criticism, if you think you know anything then explain why my argument isn't sound.

Well get prepared to eat your words, because I already did - you'll find my correct and familarly faultless analysis of the problem on page 4 of this topic.

to just argue, wrongly that mathmeticians and the like disagree with me without showing any proof is one of your usual throwaway statements

I didn't argue it - I stated it, and I stated that I accepted it.

personally i think deserve no more than they deserve.

Would you like to try that disparouging remark again - it didn't really work.

I posted as i believe no-one here has as yet answered the question correctly.

And as I've said, I'm happy for you to believe that, since you seem to operate in a crazy world of your own laws of physics and mathematics that only non-engineers can comprehend.

Why don't you open your mind to the fact that you are an interfering no nothing idiot?

Well, for two reasons: (a) I'm not an idiot and (b) I know an awful lot.

And if we're talking about interference, you were the one who came into the topic rather late.

Roll the dice again kendor - come right up and try your luck!

 

[kendor]

Softus your comments are not wanted

Yes they are - they're wanted by me.

if you have no constructive criticism, if you think you know anything then explain why my argument isn't sound.

Well get prepared to eat your words, because I already did - you'll find my correct and familarly faultless analysis of the problem on page 4 of this topic.

to just argue, wrongly that mathmeticians and the like disagree with me without showing any proof is one of your usual throwaway statements

I didn't argue it - I stated it, and I stated that I accepted it.

personally i think deserve no more than they deserve.

Would you like to try that disparouging remark again - it didn't really work.

I posted as i believe no-one here has as yet answered the question correctly.

And as I've said, I'm happy for you to believe that, since you seem to operate in a crazy world of your own laws of physics and mathematics that only non-engineers can comprehend.

Why don't you open your mind to the fact that you are an interfering no nothing idiot?

Well, for two reasons: (a) I'm not an idiot and (b) I know an awful lot.

And if we're talking about interference, you were the one who came into the topic rather late.

Roll the dice again kendor - come right up and try your luck!

As i said you are an idiot. you think it's a vertical takeoff plane from your banal answer what a prick!

 

[kendor]

So going back to the problem the only way the plane would move forwards is with the ground static which it isn't.
A treadmill wouldn't work if you were able to move forwards when running on one you'd keep hitting the control panel that's why they have speed controls so you can adjust the treadmill speed if you wish to run slower/faster.
In the plane Problem any gain in forward motion is cancelled by the runway moving you may gain a few inches each time the thrust is increased for a moment until the time lag of the sensing circuit compensates. therefore you may see a juttering forward but not enough constant speed in order to take off. but if the sensing and correcting was instantaneous then the plane would be static.

 

[hermes]

you have a different answer to every mathematician and engineer on the planet.

I'm really surprised that they all agreed to let you be their spokesman.

 

[kendor]

Bas are you going to come back on this one?

 

[Softus]

Would you like to try that disparouging remark again - it didn't really work.

As i said you are an idiot. you think it's a vertical takeoff plane from your banal answer what a p***k!

Well done kendor, not bad at all - the direct approach type of insult obviously works for you. Accuracy is still left wanting though; e.g. the following is the post that you appear to regard as banal:

Leaving aside the pun, it's not true that the wheels have no effect.

The forward thrust of a jet plane results from the jet engines, which effect can be explained using Newton's third law of motion (For every action, there is an equal and opposite reaction.).

The air resistance to the plane is the same in both scenarios, so can discounted, but the wheels encounter frictional forces, both in rubber squidging on the tarmac and in friction within the bearings.

Since the frictional force will double in the imaginary scenario of the conveyor belt (because the "ground" velocity is equal in magnitude and opposite direction to that of the plane), the only answer to be determined is whether or not the motive force of the jet engine is more than double the usual frictional force of the wheels.

I'm sure that this can be calculated, but I really can't be bothered to do that. However, the intuitive answer is that the jet force is hugely greater than the frictional force, therefore the plane will reach lift-off velocity.

Care to say which part of that was banal? Or to do with vertical take-off? Or wrong? Or superfluous? Or anything except wholly accurate and correct?

As i said you are an idiot. you think it's a vertical takeoff plane from your banal answer what a p***k!

Yup - you've certainly repeated your assertion that I'm an idiot; that much is in no doubt. The fact that you think I'm talking about vertical take-off reveals precisely who is actually the idiot though.

 

[Softus]

I'm really surprised that they all agreed to let you be their spokesman.

you have a different answer to every mathematician and engineer on the planet.

I, for one, am happy to accept that you have a different answer to every mathematician and engineer on the planet.

 

[ban-all-sheds]

Bas are you going to come back on this one?

All I can say is what's been said before.

Your analogy of the treadmill is utterly flawed, because on that your motion is caused by you acting against the treadmill, so when that moves, you remain stationary with respect to items outside the treadmill, but not to the treadmill belt itself.

Please read agan the analogy of the plane being pulled by a winch. Can you really not see that if you are winching it forward, then no matter what the runway conveyor belt does, whether it moves backwards in relattion to the plane to make the wheels spin faster, or forwards in relation to the plane to make them spin slower, or remain stationary, or even go backwards, the plane will continue to move forwards under the pull of the winch, unaffected by the motion of the runway?

Consider again my analogy of the little cart on the factory conveyor belt. Imagine the cart is so light, and has such exquisitely engineered wheels that you can push it along with hardly any effort.

Imagine you are walking along, doing just that, and then imagine the conveyor belt starting up.

If you are right, then at that point you would become incapable of pushing the cart any more. PLEASE EXPLAIN WHY.

 

[kendor]

Yup - you've certainly repeated your assertion that I'm an idiot; that much is in no doubt.

Glad to see you are finally realising it , perhaps from now on you'll keep your crass remarks to yourself

 

[kendor]

Bas are you going to come back on this one?

All I can say is what's been said before.

Your analogy of the treadmill is utterly flawed, because on that your motion is caused by you acting against the treadmill, so when that moves, you remain stationary with respect to items outside the treadmill, but not to the treadmill belt itself.

Please read agan the analogy of the plane being pulled by a winch. Can you really not see that if you are winching it forward, then no matter what the runway conveyor belt does, whether it moves backwards in relattion to the plane to make the wheels spin faster, or forwards in relation to the plane to make them spin slower, or remain stationary, or even go backwards, the plane will continue to move forwards under the pull of the winch, unaffected by the motion of the runway?

Consider again my analogy of the little cart on the factory conveyor belt. Imagine the cart is so light, and has such exquisitely engineered wheels that you can push it along with hardly any effort.

Imagine you are walking along, doing just that, and then imagine the conveyor belt starting up.

If you are right, then at that point you would become incapable of pushing the cart any more. PLEASE EXPLAIN WHY.

the treadmill is a good example bas but you are missing the point again in what you have just pointed out, ie you mention the person running acting against the treadmill, this is the energy expended in order to keep stationary(the thrust) as you said but there is the answer, the person is stationary in airspace bar the up and down motion associated with running.

the winch analogy doesn't help the problem as that it is a forward acting force not a rear acting force propelling the plane and doesn't allow the plane any backward motion, look at it this way the thrust is like a hand holding the plane from moving backwards do you agree the plane woul;d go backwards if their was no thrust but the runway control gear was set to moving, the wheels of the plane would be static and the whole craft would move backwards. the thrust is what is trying to counteract this backwards force and because of it the wheels turn. now because the wheels are turning they are gaining ground ie the circumference of the wheel is being applied to the ground each revolution, if the ground was static the plane would move forward , the trouble is for every revolution gained the ground has shifted backwards the same, hence the plane in effect has gained no ground it is in exactly the same place it was when it started. no air going over the wings means no lift.
Think of surveyors walking around measuring distance, they do it by pushing a wheel on a stick around, it's a physical thing, the mechanics of the wheel are a measuring device in effect.
the cart example i'm not sure i agree with what you say about not being able to push it anymore from what you are saying i would be on the conveyor too? if so i would have to run faster to compensate for the speed of the conveyor as i'm fixed to the cart by my hands.
if i was beside the conveyor standing on static ground then i could hold the cart stationary but it's wheels would spin ever faster and i would expend more energy in trying to do so until eventually i could not balance the equation anymore same as the thrust on the plane there would be a time when the balance could not be maintained either the conveyor would give up or you would reach maximum thrust. but we are talking ideals here and assuming that both the thrust and the conveyor have no limitations ot that they both can attain the balance ie when the plane is at max thrust the conveyor still manages to balance the equation.

If that is confusing then forget all about the thrust and forces and just think mechanics, the wheel is a measuring device but in the example what is it measuring? distance travelled of course, on solid ground it would measure the distance it has travelled over this ground and as the solid ground is static it can be used as a reference, so you can tell by the amount of revolutions what distance they have travelled over the ground.
The conveyor is moving the starting reference has shifted you can only say the wheels have travelled over distance in relation to the belt but the physical effect only relates to the belt and wheels.
you as an observer standing on static ground would perceive the ground moving under the plane also the wheels turning but the plane itself would be static to you.
maybe the confusion is coming from peoples perception that the wheels are somehow powered? they are freewheeling but the closed loop sensing of the system is looking at what speed these wheels are turning at and adjusting the conveyor accordingly. The only part that we can get a speed refence from regarding how fast the plane is wanting to move is the wheels, ie how fast they are spinning

 

[Softus]

Care to say which part of that was banal? Or to do with vertical take-off? Or wrong? Or superfluous? Or anything except wholly accurate and correct?

That would be a "no" then.

...keep your crass remarks to yourself

Simply tell me which of my remarks have been crass, and I'll gladly restate them in a less crass fashion.

For my part, I wholly retract my suggestion that you should stop posting on this topic. Your quaint analogy of the ground measuring wheel is a delight to read - I was transfixed in absolute wonder at your apparent belief that you know what you're talking about. This postulate, for example, surely deserves the Nobel Prize:

...look at it this way the thrust is like a hand holding the plane from moving backwards...

...or this one:

...it's a physical thing, the mechanics of the wheel are a measuring device in effect

And still, despite the intellectual contortions that are surely involved in creating your New Laws of Motion, through it all you continue to show empathy with the reader who may be losing grip on your frock coat tails, viz:

If that is confusing then forget all about the thrust and forces and just think mechanics...

Ever the approachable genius!

I mean, it's sheer brilliance. I reckon you must be fooling us all and you're actually a physics teacher after all. I can't tell you how much I'd like to be a student in your class.

So, kendor, please continue to set out your elegant theories of mechanics and poetic descriptions of How Stuff Works. They're really quite, er, um, ground-breaking.