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Re: Ask me a question

Unread postby davep » Tue 02 Jan 2007, 22:01:37

*Cough* Who was right?
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Re: Ask me a question

Unread postby Chicken_Little » Tue 02 Jan 2007, 22:07:33

$this->bbcode_second_pass_quote('davep', '')$this->bbcode_second_pass_quote('Chicken_Little', '')$this->bbcode_second_pass_quote('davep', '')$this->bbcode_second_pass_quote('davep', 'U')nless there was something to actually brake it, the wheels would skid and the plane would advance anyway.


Given they are frictionless, this would certainly happen.


Assume the plane remains perfectly aligned relative to the conveyor belt.


How can you assume this? The mere contact between the tyres and the conveyor belt do not mean that they will remain aligned. Indeed, this is the crux of your (recently modified) question. I say that the thrust of the engines will mean that the plane will advance and that the conveyor belt will be unable to stop it.

So there.

Unless you're saying that the force of the friction on the tyres equals that of the engines (or something, any engineers that can bail me out here?)


You're too literal minded.

This is theory.

There is no friction either in the wheels or wheel bearings. There is no friction between the tyres and the conveyor belt.

The aircraft remains perfectly aligned with the conveyor belt. The speed of the conveyor belt matches the (notional) speed of the aircraft perfectly as it attempts to take off. There is no wind.

Assume these conditions.

Can the aircraft take off?
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Re: Ask me a question

Unread postby cynicalheretic » Tue 02 Jan 2007, 22:08:48

The answer is no
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Re: Ask me a question

Unread postby davep » Tue 02 Jan 2007, 22:12:46

$this->bbcode_second_pass_quote('Chicken_Little', '')$this->bbcode_second_pass_quote('davep', '')$this->bbcode_second_pass_quote('Chicken_Little', '')$this->bbcode_second_pass_quote('davep', '')$this->bbcode_second_pass_quote('davep', 'U')nless there was something to actually brake it, the wheels would skid and the plane would advance anyway.


Given they are frictionless, this would certainly happen.


Assume the plane remains perfectly aligned relative to the conveyor belt.


How can you assume this? The mere contact between the tyres and the conveyor belt do not mean that they will remain aligned. Indeed, this is the crux of your (recently modified) question. I say that the thrust of the engines will mean that the plane will advance and that the conveyor belt will be unable to stop it.

So there.

Unless you're saying that the force of the friction on the tyres equals that of the engines (or something, any engineers that can bail me out here?)


You're too literal minded.

This is theory.

There is no friction either in the wheels or wheel bearings. There is no friction between the tyres and the conveyor belt.

The aircraft remains perfectly aligned with the conveyor belt. The speed of the conveyor belt matches the (notional) speed of the aircraft perfectly as it attempts to take off. There is no wind.

Assume these conditions.

Can the aircraft take off?

Yes. As there is no friction between the conveyor belt and the tyres, it can be considered that the conveyor belt has no equivalent braking/frictional force to oppose the force of the thrust, therefore it is irrelevant.

Or something.
Last edited by davep on Tue 02 Jan 2007, 22:15:10, edited 1 time in total.
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Re: Ask me a question

Unread postby Chicken_Little » Tue 02 Jan 2007, 22:14:11

$this->bbcode_second_pass_quote('cynicalheretic', 'T')he answer is no


you may be right but we need an explanation. otherwise it's just a 50/50 guess.
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Re: Ask me a question

Unread postby Chicken_Little » Tue 02 Jan 2007, 22:17:17

$this->bbcode_second_pass_quote('davep', '')$this->bbcode_second_pass_quote('Chicken_Little', '')$this->bbcode_second_pass_quote('davep', '')$this->bbcode_second_pass_quote('Chicken_Little', '')$this->bbcode_second_pass_quote('davep', '')$this->bbcode_second_pass_quote('davep', 'U')nless there was something to actually brake it, the wheels would skid and the plane would advance anyway.


Given they are frictionless, this would certainly happen.


Assume the plane remains perfectly aligned relative to the conveyor belt.


How can you assume this? The mere contact between the tyres and the conveyor belt do not mean that they will remain aligned. Indeed, this is the crux of your (recently modified) question. I say that the thrust of the engines will mean that the plane will advance and that the conveyor belt will be unable to stop it.

So there.

Unless you're saying that the force of the friction on the tyres equals that of the engines (or something, any engineers that can bail me out here?)


You're too literal minded.

This is theory.

There is no friction either in the wheels or wheel bearings. There is no friction between the tyres and the conveyor belt.

The aircraft remains perfectly aligned with the conveyor belt. The speed of the conveyor belt matches the (notional) speed of the aircraft perfectly as it attempts to take off. There is no wind.

Assume these conditions.

Can the aircraft take off?

Yes. As there is no friction between the conveyor belt and the tyres, it can be considered that the conveyor belt has no equivalent braking force to oppose the force of the thrust, therefore it is irrelevant.

Or something.

nice going. personally i have no clue what the answer to this question is, by the way.
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Re: Ask me a question

Unread postby davep » Tue 02 Jan 2007, 22:18:12

I've got to get to bed. Let me know if I'm right or if you've changed the rules again. :!:
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Re: Ask me a question

Unread postby davep » Tue 02 Jan 2007, 22:19:38

$this->bbcode_second_pass_quote('Chicken_Little', 'n')ice going. personally i have no clue what the answer to this question is, by the way.


I want to strangle you slowly. With no friction. Will it work?
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Re: Ask me a question

Unread postby cynicalheretic » Tue 02 Jan 2007, 22:21:33

with no friction or lift, the plane will not take off. The plane taxi's down the run way to get lift, otherwise it is all for nada
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Re: Ask me a question

Unread postby davep » Tue 02 Jan 2007, 22:23:28

$this->bbcode_second_pass_quote('cynicalheretic', 'w')ith no friction or lift, the plan will not take off. The plane taxi's down the run way to get lift, otherwise it is all for nada


You're way behind here, O Great Oracle. No friction - check. No lift - why not?
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Re: Ask me a question

Unread postby Chicken_Little » Tue 02 Jan 2007, 22:25:57

$this->bbcode_second_pass_quote('cynicalheretic', 'w')ith no friction or lift, the plane will not take off. The plane taxi's down the run way to get lift, otherwise it is all for nada


the plane will have lift. assuming a frictionless conveyor belt and frictionless wheels and wheel bearings, the aircraft will take off due to the thrust generated by its engines.

In fact, with no friction, it's irrelevant how fast the conveyor belt is moving.
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Re: Ask me a question

Unread postby davep » Tue 02 Jan 2007, 22:30:59

< kicks cynicalheretic aside >

I'll be answering further questions tomorrow. 8)
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Re: Ask me a question

Unread postby cynicalheretic » Tue 02 Jan 2007, 22:36:10

$this->bbcode_second_pass_quote('davep', '')$this->bbcode_second_pass_quote('cynicalheretic', 'w')ith no friction or lift, the plan will not take off. The plane taxi's down the run way to get lift, otherwise it is all for nada


You're way behind here, O Great Oracle. No friction - check. No lift - why not?



a wing generates lift because it deflects the airflow
or just look up the Bernoulli principle -- This is all just freshmen physics.

You are just wasting my time with silly questions.
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Re: Ask me a question

Unread postby Chicken_Little » Tue 02 Jan 2007, 22:39:46

$this->bbcode_second_pass_quote('cynicalheretic', '')$this->bbcode_second_pass_quote('davep', '')$this->bbcode_second_pass_quote('cynicalheretic', 'w')ith no friction or lift, the plan will not take off. The plane taxi's down the run way to get lift, otherwise it is all for nada


You're way behind here, O Great Oracle. No friction - check. No lift - why not?



a wing generates lift because it deflects the airflow
or just look up the Bernoulli principle -- This is all just freshmen physics.

You are just wasting my time with silly questions.



lift will be generated because assuming frictionless wheels etc the plane will take off due to engine thrust, regardless of any conveyor belts.
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Re: Ask me a question

Unread postby cynicalheretic » Tue 02 Jan 2007, 22:44:14

Yes, you are right... I was looking at the damn question all wrong. Yes the plane will take off. I feel like a damn idiot now that I think about it. In a vaccum though the plane would never take off. So I am going to pretend I thought it was in a vaccum
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Re: Ask me a question

Unread postby cynicalheretic » Tue 02 Jan 2007, 22:45:57

Physics plays tricks on us. The planes engines are not turning the wheels but pushing/pulling the fuselage of the plane. The plane will move foreword regardless of the speed of the conveyor.

Wheel speed= w = p+c = p2 = c2
Plane speed = p = c
conveyor speed = c = p
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Re: Ask me a question

Unread postby cynicalheretic » Tue 02 Jan 2007, 22:52:23

New question.
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Re: Ask me a question

Unread postby Chicken_Little » Tue 02 Jan 2007, 22:56:09

$this->bbcode_second_pass_quote('cynicalheretic', 'P')hysics plays tricks on us. The planes engines are not turning the wheels but pushing/pulling the fuselage of the plane. The plane will move foreword regardless of the speed of the conveyor.

Wheel speed= w = p+c = p2 = c2
Plane speed = p = c
conveyor speed = c = p



No it won't unless we assume (as we did earlier) that most aspects of the interaction between the plane's wheels and the conveyor belt are frictionless.

Think of it this way. Why do we bother with runways if planes could take off from much shorter conveyor belts?
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Re: Ask me a question

Unread postby cynicalheretic » Tue 02 Jan 2007, 22:58:31

Trust me, unless the wheels explode it will work. I am willing to bet you $50,000.00 that I am correct. I just screwed up my logic earlier.

You are thinking in terms of a car, but with a plane you have air friction and regardless what direction and how fast the tires are going in reverse the plane itself will take off
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Re: Ask me a question

Unread postby Chicken_Little » Tue 02 Jan 2007, 23:08:34

$this->bbcode_second_pass_quote('cynicalheretic', 'T')rust me, unless the wheels explode it will work. I am willing to bet you $50,000.00 that I am correct. I just screwed up my logic earlier.

You are thinking in terms of a car, but with a plane you have air friction and regardless what direction and how fast the tires are going in reverse the plane itself will take off


the plane will certainly take off if we assume no friction between the conveyor belt and the wheels or in the wheel bearings etc, due to newtonian physics (engine thrust makes it take off).

if we're talking about a normal plane trying to take off on a conveyor belt moving in the opposite direction, perfectly matched to the aircraft's notional ground speed, then the aircraft can't get any lift because it's not moving relative to the surrounding air and its energy is being absorbed just keeping up with the conveyor belt + friction effects.
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