Riddle Me This......... - Page 14

bob^ · 01-12-2005, 10:58 PM

Quote:

Originally Posted by Casper

its irrelevant
fact is that there is only one answer that can be convincingly stated without a logic flaw.. the plane will take off.. conveyor is irrelevant.

Exactly, its as relevant as the friction in the wheels. I don't see why its so hard to understand that the plane will take off.

Sourbastard · 01-12-2005, 11:11 PM

Quote:

Originally Posted by 42.57lb

Just before you do that, explain to me how a plane stops when it lands????

Reverse Thrust, air brakes, Flaps. How do you stop a plane? Harsh language?

42.57lb · 01-12-2005, 11:13 PM

Quote:

Originally Posted by sourbastard

Reverse Thrust, air brakes, Flaps. How do you stop a plane? Harsh language?

so the wheels have absolutely no bearing on whether the plane stops or not? By the way, all those things generate friction. Maybe not directly with the tarmac, but they do.

I used to swear at planes, now I just swear at bell ends that can't drive

Sourbastard · 01-12-2005, 11:20 PM

Engines, flaps and air brakes generate friction against the atmosphere not the ground.

The brakes on an aircraft are for precise maneuvering at low speed when the engines are at very low or no power, they are not major components of slowing the aircraft when landing.

flappist · 01-12-2005, 11:23 PM

Quote:

Originally Posted by 42.57lb

so the wheels have absolutely no bearing on whether the plane stops or not? By the way, all those things generate friction. Maybe not directly with the tarmac, but they do.

I used to swear at planes, now I just swear at bell ends that can't drive

http://www.aeroclub.com.au/queryao-70.html

Why don't you go and find out?

42.57lb · 01-12-2005, 11:23 PM

The plane with not fly.The plane with not fly.The plane with not fly.The plane with not fly.The plane with not fly.The plane with not fly.The plane with not fly.The plane with not fly.The plane with not fly.The plane with not fly.The plane with not fly.The plane with not fly.The plane with not fly.The plane with not fly.The plane with not fly.The plane with not fly.The plane with not fly.The plane with not fly.The plane with not fly.

42.57lb · 01-12-2005, 11:23 PM

ok. Now, please excuse me while I go and smash my face on a brick wall.

Won't be a tick!

42.57lb · 01-12-2005, 11:26 PM

Quote:

Originally Posted by flappist

http://www.aeroclub.com.au/queryao-70.html

Why don't you go and find out?

do you think they have one of those coveyerbelt run ways?

Sourbastard · 01-12-2005, 11:27 PM

Quote:

Originally Posted by 42.57lb

do you think they have one of those coveyerbelt run ways?

no but they might have a sturdy brick wall for you to brain yourself on.

**Charliewool** · 01-12-2005, 11:33 PM

Quote:

Originally Posted by PetesV8

This has been a very amusing thread!!!! With what appear to be logical arguments on both sides.
As many have pointed out, this question is purely theoretical, as in practice you could not replicate the conditions as stated in the question.

Perhaps the following scenarios will enlighten

a) car on the 1/4 , 100 kph trap speed. (ss commodore LOL)

Q1. What would happen if at the end of the 1/4 this theoretical conveyor system was turning in the opposite direction @ 150kph? ie car @ 150 meets conveyor @ 150?
Q2. Same scenario above but car @ 300 and conveyor @ 150?
Q3. Same scenario but car @ 150 and conveyor @ 300

Before people start jumping up and down about how a car drives through its wheels, replace car with rocket powered drag car!

Uh huh!.. But in our scenario the wheels are on the above said conveyor constantly..NOT at the end.
And, I reckon in YOUR scenario (all 3), I'd put my foot on the clutch or throw it into angel gear quickly!... Just keep them wheels freewheeling (which would ALSO encompass your rocket car thingo)

eb91xr6 · 01-12-2005, 11:41 PM

Malakai got it first so for every one who repeted what he said give him some credit

**Charliewool** · 01-12-2005, 11:54 PM

What.. Like a medal?? ... Please!
And I don't think anyone "repeted" what he said?..

**Charliewool** · 02-12-2005, 12:17 AM

I should amend that by saying that.. If ANYONE deserves a medal here, It's Casper for plugging away, and attempting to instill some reasoning into some of the boneheads here. Still though, I think FRY big pete for starting this!
(apologies to eb91xr6... NO malice directed at you mate)

THORNSPAWN · 02-12-2005, 05:38 AM

Ok I believe I have solved it
Those who thought it WILL take off are still correct, although some of the arguements
are not (including mine)

The conveyor is running at the same speed as the plane but in the opposite direction.

OK Simple. The conveyor never moves and the plane takes off as normal.

Want to hear more?
Look out the window of your car while you're driving, what is the ground and every
other stationary object doing in relation to the car? It's moving in the opposite direction
at the exact speed as the car.
So imagine you were on the plane on the conveyor doing 100kph and look out
the window at the conveyor, what speed is it doing? In relation to the plane it will be moving
at 100kph in the opposite direction along with the ground, the air, the
airport, sourbastards teapots and the 1st AFF Big Pete BBQ.

It is not, as I originally thought, going twice as fast relative to the plane
and the same speed relative to the ground as the plane is, also relative to the ground,
as then the conveyor will be doing double the speed of the plane when the question states
it does the same speed in the opposite direction.

The conveyor doesn't move in relation to the ground, it moves in relation to the plane.
Just like everything else will.
The same scenario will still be true with or without the conveyor.
Say the plane is on a normal runway, as the plane accelerates so does the ground
in the opposite direction, in relation to the plane, no matter what speed the plane
was doing the runway will be doing the same speed in the opposite direction, in
relation to the plane.

Plane...................------100-------> relative to everything else
conveyor.............<-----100-------- relative to the plane
air......................<-----100-------- relative to the plane
ground................<-----100-------- relative to the plane
airport.................<-----100------- relative to the plane
teapots...............<-----100------- relative to the plane
BBQ....................<-----100------- relative to the plane

Now, what is the conveyor doing relative to the plane?
100 in the opposite direction (the SAME speed as the plane).
what is the conveyor doing in relation to everything else?
0 it's stationary compared to everything other than the plane.

I've been pondering this all day and I'm surprised I didn't think of this before.
What do you all think of THAT one?

02-12-2005, 06:01 AM

Quote:

Originally Posted by 42.57lb

dude, I've already conceded that I can't explain it. Show me the numbers, go on, get yourself a model plane and a treadmill, then hook up the throttle of the plane to a sensor in the treadmill, tape it, post it on geocities and BAM, I'm completely shot down.

Just before you do that, explain to me how a plane stops when it lands???? Has it going ANYTHING AT ALL to do with friction.

I dare you to say no

It doesn't need numbers, it is simple mathematics! Twice the wheel speed, twice the wheel friction to overcome. If that is enough to stop the plane moving, then at half wheel speed (a normal takeoff) half of the plane's energy is being used to overcome wheel / bearing friction, which is a ridiculous concept.

In regards to the plane stopping when it lands, as mentioned, the wheels play a very small part in this again. Even if you do consider the braking force from the wheels, it is a completely different scenario, as they now have some effect on the plane's speed as the brakes are applied, and therefore the wheels cannot spin freely. In the same way that if the brakes were applied while the plane sat stationary on the moving conveyor, it would move backwards. You are changing the wheels from a part that has no baring on the plane to one which does WHEN the brakes are applied. When they brakes are not applied, the wheel speed has no bearing whatsoever on the planes motion.

FTGAutosalvage · 02-12-2005, 09:16 AM

think of it this way. chuck a car on a dyno... you can red line it in 5th and not get anywhere... the dyno is behaving like our conveyer belt.

now get a tow rope and attach it to the car and start towing... your car will move off the dyno, even though the dyno is stopping wheelspeed from moving you. the towing car is acting like the jet engines... applying force that is independant of anything the ground can do

LTDHO · 02-12-2005, 10:53 AM

Quote:

Originally Posted by FTGAutosalvage

think of it this way. chuck a car on a dyno... you can red line it in 5th and not get anywhere... the dyno is behaving like our conveyer belt.

now get a tow rope and attach it to the car and start towing... your car will move off the dyno, even though the dyno is stopping wheelspeed from moving you. the towing car is acting like the jet engines... applying force that is independant of anything the ground can do

Umm, no. the towing car has direct contact with the ground. not floationg in the air

I contacted the Business Development Manager of Strategic Data Pty Ltd for his professional oppinion

Quote:

Ok.. think its time I give up on this little hyperthetical...

but ...

soem comments from an engineer - who doesnt work in this area (you
knonw, the area of trying to get planes to take off while standing
still!).. but I knew he'd be into thinking about it and making comments.

I think we are confusing a car with a plane. The wheels on a plane are
free moving - so unless the engines push the wings & body of the plane
forward the wheels aren't going to turn anyway. . . hence your
hypothetical conveyor can modify the rotation speed of the wheels - but
doesn't impact on the speed of the wings.

Addressing the point of the engines creating airflow over the wings:
* I haven't seen any plane that has been built in such a way as to
create airflow over the wings (generally they have a significant
physical separation from the wing - and in the case of jets are
positioned behind the wing (its never a good idea to melt the thing you
are using to keep you up in the air)

* There are significant inefficiencies in the conversion of airflow to
lift, which means that you would need really big propellers to create
sufficient airflow to create sufficient lift - it would end up being
more effective as another design you are familiar with - a helicopter.

To two peaople in the field say No.

FTGAutosalvage · 02-12-2005, 11:32 AM

ok then

use a winch on the front of a 4wd to pull the car . it WILL move forward

Black XR6 · 02-12-2005, 11:49 AM

I love these hypothetical what if scenarios.

I would like to now admit the plane would indeed take off. The wheels are only there to support the plane and stop it crashing on landing. I just thought it throw in another against argument to continue the debate further.

Cheers

Heard a good one on the telly not too long ago though.

It goes, If you try to fail and a succeed, which one have you done?

cArSiK · 02-12-2005, 12:11 PM

Once again the Plain Will Take Off

http://www.airliners.net/discussions...d.main/136068/

From a forum full of Commercial Pilots / Engineers

cArSiK · 02-12-2005, 12:26 PM

Quote:

Originally Posted by cArSiK

Once again the Plain Will Take Off

http://www.airliners.net/discussions...d.main/136068/

From a forum full of Commercial Pilots / Engineers

I should add , provided the gear can take the stresses :eclipsee_

THORNSPAWN · 02-12-2005, 02:39 PM

:

:
Did anyone bother to read my previous post?
THE CONVEYOR DOESN'T MOVE AT ALL!!!
It was a trick question!!!

Casper · 02-12-2005, 02:58 PM

Quote:

Originally Posted by THORNSPAWN

:

:
Did anyone bother to read my previous post?
THE CONVEYOR DOESN'T MOVE AT ALL!!!
It was a trick question!!!

Read post 390... we've already been there about 30 posts before you got there.

THORNSPAWN · 02-12-2005, 03:03 PM

Quote:

Originally Posted by Casper

Read post 390... we've already been there about 30 posts before you got there.

My appologies Casper let me rephrase that

THE CONVEYOR DOESN'T MOVE AT ALL AND THE PLANE TAKES OFF AS PER NORMAL!!!

AU1FORME · 02-12-2005, 03:03 PM

Quote:

Originally Posted by BlackLS

It will take off.. A plane uses air for displacement to move forward. The wheels of it would just be spinning like crazy tho...

It uses air flow to create lift, if the thing is not moving in a forward direction it cannot create airflow over the wings do there for cannot creat lift

thanks for listening

Casper · 02-12-2005, 03:09 PM

Quote:

Originally Posted by AU1FORME

It uses air flow to create lift, if the thing is not moving in a forward direction it cannot create airflow over the wings do there for cannot creat lift

thanks for listening

Do I REALLY need to go through this again?

Ok. here we go.

The conveyor will move at the same forward speed as the plane countering all movement right?

And the conveyor is designed to travel exactly at the same speed the plane is moving forward thus making the plane stand still right? Therefore making no lift.

How fast is the plane moving forward? The answer has to be zero mph because its stuck on a conveyor.

Do you agree with this?

FTGAutosalvage · 02-12-2005, 03:12 PM

the question is will the plane take off.

the answer to this is YES

THORNSPAWN · 02-12-2005, 03:27 PM

You could have 10 planes on the conveyor all doing different speeds
What speed is the conveyor doing In relation to each plane?
It's going the same speed as each plane in the opposite direction
relative to each plane NOT the ground.
The conveyor is not even moving at all relative to the ground.

Casper · 02-12-2005, 03:30 PM

Quote:

Originally Posted by THORNSPAWN

You could have 10 planes on the conveyor all doing different speeds
What speed is the conveyor doing In relation to each plane?
It's going the same speed as each plane in the opposite direction
relative to each plane NOT the ground.
The conveyor is not even moving at all relative to the ground.

lets, for humour sake, assume the conveyor is moving the exact speed of the plane in reverse relative to the actual ground. Therefore if the plane is going 100mph forward the converyor is going 100mph backwards.. in relation to a fixed point on the real ground. I think this is how the riddle was intended.

42.57lb · 02-12-2005, 03:41 PM

this is what happens