Going to settle the plane on a treadmill once and for all. - Page 2

ballz2wallz · 01-22-2007, 05:05 PM

Originally Posted by nbiggershaft

NO IT DOESN'T. FRICTION HAS ABSOLUTELY NOTHING TO DO WITH ACCELERATING A PLANE. A car, which has a drive train attached to the wheels uses friction to accelerate, a person uses friction to accelerate. A PLANE PUSHES AIR TO ACCELERATE. It acts the same as a rocket. Push air one way, you move the other.

Look, when the jets propel the plane, how does it move? The wheels...if the plane begins to push forward, but the friction of the tires moves the treadmill under the plane instead of the plane through the air, then it will not create lift. You're thinking of this in the wrong way; yes, you're right, the tires create no friction themselves as there is no engine, but the jet propels the plane across the ground via THE TIRES, friction from the tires on the ground, which gives it enough lift. If the ground moves intead of the plane, there is no lift created!

nbiggershaft · 01-22-2007, 05:12 PM

Originally Posted by ballz2wallz

Look, when the jets propel the plane, how does it move? The wheels...if the plane begins to push forward, but the friction of the tires moves the treadmill under the plane instead of the plane through the air, then it will not create lift. You're thinking of this in the wrong way; yes, you're right, the tires create no friction themselves as there is no engine, but the jet propels the plane across the ground via THE TIRES, friction from the tires on the ground, which gives it enough lift. If the ground moves intead of the plane, there is no lift created!

sigh....
Plane Problem (explained by Moz) | Playing ignorant..
Plane Problem (explained by Moz) | Playing ignorant..
Plane Problem (explained by Moz) | Playing ignorant..
Plane Problem (explained by Moz) | Playing ignorant..
Plane Problem (explained by Moz) | Playing ignorant..
Plane Problem (explained by Moz) | Playing ignorant..
Plane Problem (explained by Moz) | Playing ignorant..

ballz2wallz · 01-22-2007, 05:14 PM

Dude I'm not clicking that link anymore as it freezes up my comp everytime I do. aka I can't read it.

ballz2wallz · 01-22-2007, 05:18 PM

I have a question: is the treadmill on or off? Cause I was under the impression it was on and moving, and the jets were only causing a balance force. If the treadmill was off and left to the jets, then yes, the plane would be able to take off, and the treadmill would not move.

sorry. I could be wrong if I didn't understand what you were talking about.

Silly me...I was picturing a treadmill like the ones at the gym. I think the plane would take off.

nbiggershaft · 01-22-2007, 05:25 PM

Originally Posted by ballz2wallz

I have a question: is the treadmill on or off? Cause I was under the impression it was on and moving, and the jets were only causing a balance force. If the treadmill was off and left to the jets, then yes, the plane would be able to take off, and the treadmill would not move. sorry. I could be wrong if I didn't understand what you were talking about.

Silly me...I was picturing a treadmill like the ones at the gym. I think the plane would take off.

No you still have the right idea. The treadmill runs like the one at the gym. You just have the wrong idea about causes a plane to move forward.

motivez · 01-22-2007, 05:29 PM

Man, we should write Mythbusters and get them to do this.

7960 · 01-22-2007, 05:30 PM

Originally Posted by nbiggershaft

You guys aren't visualizing this right. Imagine you have a toy car on a treadmill. You push it with your finger(the planes jet engines) while the treadmill is running opposite to you. The wheels freely spin but the car moves forward because the force of your finger is much higher than the friction in the bearings of the toy cars wheels.

this is the best example to try to get the example through to people.

ballz, a treadmill is running. put a matchbox car on the treadmill with your finger behind the car so it's stationary. speed up the treadmill, slow it down, whatever...you will be able to push the car faster than the treadmill is spinning so you will be able to move the car forward.

that's analogous to the plane...the wheels are free-spinning. as you turn up the thrust on the plane the treadmill spins and the wheels go at an equal and opposite speed. but as you turn up the thrust on the plane it moves forward even as the treadmill spins even faster (just like the car, the wheels just turn faster).

all that assumes no friction............... add in friction and the whole game changes.

ballz2wallz · 01-22-2007, 05:32 PM

Originally Posted by 7960

this is the best example to try to get the example through to people.

ballz, a treadmill is running. put a matchbox car on the treadmill with your finger behind the car so it's stationary. speed up the treadmill, slow it down, whatever...you will be able to push the car faster than the treadmill is spinning so you will be able to move the car forward.

that's analogous to the plane...the wheels are free-spinning. as you turn up the thrust on the plane the wheels don't do shit. the treadmill spins, the wheels go at an equal and opposite speed, but as you turn up the thrust on the plane it moves forward even as the treadmill spins even faster (just like the car, the wheels just turn faster).

all that assumes no friction............... add in friction and the whole game changes.

Yes, I know you can get the plane faster than the treadmill, but you have to reach a certain speed in order to create the right amount of wind to create lift. This is done based on the speed of which it moves ON THE GROUND. The jets may be at full power, but if the plane only advances 1 ft. per min it won't take off.

ballz2wallz · 01-22-2007, 05:32 PM

Originally Posted by nbiggershaft

No you still have the right idea. The treadmill runs like the one at the gym. You just have the wrong idea about causes a plane to move forward.

Then no, it won't work.

7960 · 01-22-2007, 05:35 PM

Originally Posted by ballz2wallz

Yes, I know you can get the plane faster than the treadmill, but you have to reach a certain speed in order to create the right amount of wind to create lift. This is done based on the speed of which it moves ON THE GROUND. The jets may be at full power, but if the plane only advances 1 ft. per min it won't take off.

with absolutely no friction in the wheels/bearings the plane will take off becuase there will be nothing to drag it backwards as the plane accelerates.

the only question is what role friction plays.

ballz2wallz · 01-22-2007, 05:37 PM

Originally Posted by 7960

with absolutely no friction in the wheels/bearings the plane will take off becuase there will be nothing to drag it backwards as the plane accelerates.

the only question is what role friction plays.

Friction is always a factor.

7960 · 01-22-2007, 05:39 PM

Originally Posted by ballz2wallz

Friction is always a factor.

... that's why I've said three times now friction is the key. IF THERE IS NO FRICTION in the wheels/bearings then the plane takes off. BECAUSE THERE IS FRICTION in the wheels/bearings then the problem gets muddied.

ballz2wallz · 01-22-2007, 05:48 PM

Originally Posted by 7960

... that's why I've said three times now friction is the key. IF THERE IS NO FRICTION in the wheels/bearings then the plane takes off. BECAUSE THERE IS FRICTION in the wheels/bearings then the problem gets muddied.

But even then I disagree...even in a frictionless system, if the treadmill is on, and the plane is only moving a little bit faster than the treadmill, enough lift won't be achieved. It seems simple to me, but then again I'm not physics man.

7960 · 01-22-2007, 05:59 PM

Originally Posted by ballz2wallz

But even then I disagree...even in a frictionless system, if the treadmill is on, and the plane is only moving a little bit faster than the treadmill, enough lift won't be achieved.

I'll draw a picture (not as nice as nbigger's

)

if there was no friction in the wheels/bearing the plane would take off at the EXACT SAME SPOT as a traditional plane if the treadmill was turned off and locked.

Ardentfrost · 01-22-2007, 06:51 PM

Wait, why would the treadmill move at all? I mean, isn't the thrust of the jets propelling the plane, therefore the treadmill would have no effect whatsoever? A treadmill affecting the movement of the plane would mean that the motile function of the plane generated from its wheels, but it actually generates from it's wings, right?

I'm not an aerospace engineer, that's just how it seems to me.

ballz2wallz · 01-22-2007, 08:02 PM

Originally Posted by 7960

I'll draw a picture (not as nice as nbigger's )

if there was no friction in the wheels/bearing the plane would take off at the EXACT SAME SPOT as a traditional plane if the treadmill was turned off and locked.

You've not accounted for the force of wind needed to create enough lift to take off. You're placing too much emphasis on the wheels and not enough on the wind.

imind · 01-22-2007, 09:10 PM

7960 · 01-22-2007, 11:15 PM

Originally Posted by ballz2wallz

You've not accounted for the force of wind needed to create enough lift to take off. You're placing too much emphasis on the wheels and not enough on the wind.

no

if there was no friction in the wheels/bearings then the plane would accelerate and take off EXACTLY like a plane on a regular runway. The pilot wouldn't notice a thing unless he looked directly down at the runway, the passengers would see the trees go by EXACTLY like any other "normal" flight.......... the plane would behave EXACTLY like any other plane.

wheels/friction are what put a twist in but let's get past this no-friction problem first, ok?

7960 · 01-22-2007, 11:17 PM

Originally Posted by Ardentfrost

Wait, why would the treadmill move at all?

the scenario says the treadmill is set to go exactly the same speed as the plane only in the other direction

Kytro · 01-22-2007, 11:20 PM

Seaplanes have no wheels and they take off fine.

Unless the treadmill was matching the wheel speed the friction on the bearings would unlikely to bee effective