think about this... [Archive] - Two Plus Two Older Archives

MelK

11-23-2005, 09:41 AM

[ QUOTE ]
Airspeed = 0 the plane cannot take off. This would be the same if the plane had a tail wind that was = to it's forward motion.

[/ QUOTE ]

Good answer, but just seconds too slow. /images/graemlins/grin.gif

edit:
I see Ray has altered the OP to provide some of the lacking information. My "insufficient information" answer was clearly the correct one. /images/graemlins/wink.gif

mostsmooth

11-23-2005, 09:42 AM

this doesnt require much thought

Slow Play Ray

11-23-2005, 09:42 AM

[ QUOTE ]
this doesnt require much thought

[/ QUOTE ]

so what's your answer? maybe it requires more thought than you're giving it credit for.

mostsmooth

11-23-2005, 09:49 AM

[ QUOTE ]
[ QUOTE ]
this doesnt require much thought

[/ QUOTE ]

so what's your answer? maybe it requires more thought than you're giving it credit for.

[/ QUOTE ]
if im reading your question right, it will absolutely take off
maybe im stupid
/images/graemlins/confused.gif

mostsmooth

11-23-2005, 09:52 AM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
this doesnt require much thought

[/ QUOTE ]

so what's your answer? maybe it requires more thought than you're giving it credit for.

[/ QUOTE ]
if im reading your question right, it will absolutely take off
maybe im stupid
/images/graemlins/confused.gif

[/ QUOTE ]
and if im stupid, im stupid!!!

Slow Play Ray

11-23-2005, 09:53 AM

[ QUOTE ]
Airspeed = 0 the plane cannot take off. This would be the same if the plane had a tail wind that was = to it's forward motion.

[/ QUOTE ]

this is not true.

Blarg

11-23-2005, 09:53 AM

If the plane is not moving, no air is being forced under its wings. If no air is being forced under its wings, there is no lift. So it stays grounded.

If a car were going 60 miles an hour and you stuck your head out the window, you'd feel a strong breeze in your face. Put the car on a treadmill that equalizes the speed, stick your head out the window, and you won't feel the wind rush through your hair.

FouTight

11-23-2005, 09:54 AM

The problem with this scenario is that the drive isn't created by the wheels, so this belt wouldn't result in the plane not moving, it would mean the wheels would be moving REALLY quickly, but the thrust would still push teh plane forward.

This scenario is impossible.

stigmata

11-23-2005, 09:55 AM

http://wwwsam.brooks.af.mil/af/files/fsguide/HTML/Graphics/fig_28-10.gif

Slow Play Ray

11-23-2005, 10:00 AM

[ QUOTE ]
If the plane is not moving, no air is being forced under its wings. If no air is being forced under its wings, there is no lift. So it stays grounded.

[/ QUOTE ]

When did I say the plane wasn't moving?

Eurotrash

11-23-2005, 10:03 AM

[ QUOTE ]
[ QUOTE ]
If the plane is not moving, no air is being forced under its wings. If no air is being forced under its wings, there is no lift. So it stays grounded.

[/ QUOTE ]

When did I say the plane wasn't moving?

[/ QUOTE ]

you essentially gave us two velocity vectors of equal magnitude that work in exactly opposite directions. the plane has zero velocity relative to somebody standing on the ground observing it. it is going nowhere.

i think.

Slow Play Ray

11-23-2005, 10:05 AM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
If the plane is not moving, no air is being forced under its wings. If no air is being forced under its wings, there is no lift. So it stays grounded.

[/ QUOTE ]

When did I say the plane wasn't moving?

[/ QUOTE ]

you essentially gave us two velocity vectors of equal magnitude that work in exactly opposite directions.

[/ QUOTE ]

All I really told you is that the conveyor belt velocity and the wheels' tangential velocity are equal, essentially. But does this address the plane's velocity?

FouTight

11-23-2005, 10:07 AM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
If the plane is not moving, no air is being forced under its wings. If no air is being forced under its wings, there is no lift. So it stays grounded.

[/ QUOTE ]

When did I say the plane wasn't moving?

[/ QUOTE ]

you essentially gave us two velocity vectors of equal magnitude that work in exactly opposite directions. the plane has zero velocity relative to somebody standing on the ground observing it. it is going nowhere.

i think.

[/ QUOTE ]

Everyone seems to be figuring this from the standpoint that the plane's wheels are where the thrust is comming from. The wheels do not push the plane forward, the props do.

Eurotrash

11-23-2005, 10:09 AM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
If the plane is not moving, no air is being forced under its wings. If no air is being forced under its wings, there is no lift. So it stays grounded.

[/ QUOTE ]

When did I say the plane wasn't moving?

[/ QUOTE ]

you essentially gave us two velocity vectors of equal magnitude that work in exactly opposite directions.

[/ QUOTE ]

All I really told you is that the conveyor belt velocity and the wheels' rotational velocity are equal, essentially. But does this address the plane's velocity?

[/ QUOTE ]

i'm misunderstanding the way you're phrasing this, I suppose. the comments I made above assumed that the forward velocity of the plane was exactly canceled by the reverse velocity of the conveyor.

I thought your original post was implying that with a setup like this one could get the plane to take off vertically like a harrier jet without the vertical engines

11-23-2005, 10:12 AM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
If the plane is not moving, no air is being forced under its wings. If no air is being forced under its wings, there is no lift. So it stays grounded.

[/ QUOTE ]

When did I say the plane wasn't moving?

[/ QUOTE ]

you essentially gave us two velocity vectors of equal magnitude that work in exactly opposite directions. the plane has zero velocity relative to somebody standing on the ground observing it. it is going nowhere.

i think.

[/ QUOTE ]

Everyone seems to be figuring this from the standpoint that the plane's wheels are where the thrust is comming from. The wheels do not push the plane forward, the props do.

[/ QUOTE ]

Why is that relevant? The thrust from the props = X. The "thrust" from the moving conveyor-runway = -X. The aircraft is not moving relative to the air. Hence, no airspeed, so no lift.

Slow Play Ray

11-23-2005, 10:13 AM

so do you get it now?

Slow Play Ray

11-23-2005, 10:13 AM

[ QUOTE ]
The thrust from the props = X. The "thrust" from the moving conveyor-runway = -X.

[/ QUOTE ]

this is wrong.

Eurotrash

11-23-2005, 10:13 AM

[ QUOTE ]
Everyone seems to be figuring this from the standpoint that the plane's wheels are where the thrust is comming from. The wheels do not push the plane forward, the props do.

[/ QUOTE ]

no. I understand what causes the plane to move forward.

Running Bad

11-23-2005, 10:18 AM

What everyone is missing is that the plane is attached to a hook on a launching arm, and the runway is oiled and there is a very low coefficient of friction. The wheels are just spinning wildly, it just happens to be the same speed as the conveyor belt. I hope this makes it easier to understand. /images/graemlins/grin.gif

Cheers,
Rube Goldberg

Mars357

11-23-2005, 10:22 AM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
If the plane is not moving, no air is being forced under its wings. If no air is being forced under its wings, there is no lift. So it stays grounded.

[/ QUOTE ]

When did I say the plane wasn't moving?

[/ QUOTE ]

you essentially gave us two velocity vectors of equal magnitude that work in exactly opposite directions. the plane has zero velocity relative to somebody standing on the ground observing it. it is going nowhere.

i think.

[/ QUOTE ]

Everyone seems to be figuring this from the standpoint that the plane's wheels are where the thrust is comming from. The wheels do not push the plane forward, the props do.

[/ QUOTE ]

Why is that relevant? The thrust from the props = X. The "thrust" from the moving conveyor-runway = -X. The aircraft is not moving relative to the air. Hence, no airspeed, so no lift.

[/ QUOTE ]

I agree, ground speed has nothing to do with it. It's all about airspeed (the speed at which air passes over the wing). Nothing else matters.

If an plane is moving forward at 50 MPH into a headwind of 100 MPH, the net airspeed is 150 MPH BUT the plane would actually be moving backwards at a rate of 50 MPH groundspeed....

FouTight

11-23-2005, 10:27 AM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
If the plane is not moving, no air is being forced under its wings. If no air is being forced under its wings, there is no lift. So it stays grounded.

[/ QUOTE ]

When did I say the plane wasn't moving?

[/ QUOTE ]

you essentially gave us two velocity vectors of equal magnitude that work in exactly opposite directions. the plane has zero velocity relative to somebody standing on the ground observing it. it is going nowhere.

i think.

[/ QUOTE ]

Everyone seems to be figuring this from the standpoint that the plane's wheels are where the thrust is comming from. The wheels do not push the plane forward, the props do.

[/ QUOTE ]

Why is that relevant? The thrust from the props = X. The "thrust" from the moving conveyor-runway = -X. The aircraft is not moving relative to the air. Hence, no airspeed, so no lift.

[/ QUOTE ]

I agree, ground speed has nothing to do with it. It's all about airspeed (the speed at which air passes over the wing). Nothing else matters.

If an plane is moving forward at 50 MPH into a headwind of 100 MPH, the net airspeed is 150 MPH BUT the plane would actually be moving backwards at a rate of 50 MPH groundspeed....

[/ QUOTE ]

too bad, i'm right.

Slow Play Ray

11-23-2005, 10:29 AM

[ QUOTE ]
i'm right.

[/ QUOTE ]

this is true - you seem to be the only one grasping it so far. out of curiosity, what is your job/major?

FouTight

11-23-2005, 10:30 AM

[ QUOTE ]
[ QUOTE ]
i'm right.

[/ QUOTE ]

this is true - you seem to be the only one grasping it so far. out of curiosity, what is your job/major?

[/ QUOTE ]

Computer tech/networking/misc

fnord_too

11-23-2005, 10:38 AM

If a plane (specifically its wings) is traveling with zero speed with respect to the air, then there can be no lift. If the props are forcing air over the wings, there can be lift (though then the plane is not traveling with zero speed wrt the air, so we don't contradict the above). If you have some VTOL capabilities (really just VT) you could take off. I think in the scenario you described, you cannot, though I am not sure how much air the props push over the wings.

The discussion in this thread makes me think perhaps your phrasing is awkward.

mostsmooth

11-23-2005, 10:43 AM

[ QUOTE ]
[ QUOTE ]
i'm right.

[/ QUOTE ]

this is true - you seem to be the only one grasping it so far. out of curiosity, what is your job/major?

[/ QUOTE ]
dude, i grasped it too!!!

FouTight

11-23-2005, 10:44 AM

[ QUOTE ]

The discussion in this thread makes me think perhaps your phrasing is awkward.

[/ QUOTE ]

I agree with this, the OP is a bit convoluted, but everyone is seeing this as some sort of runnign on a treadmill scenario, when it really isn't.

Slow Play Ray

11-23-2005, 10:47 AM

[ QUOTE ]
The discussion in this thread makes me think perhaps your phrasing is awkward.

[/ QUOTE ]

I think everyone here understands what makes a plane lift. The question is - can lift be created in this scenario?

My wording was intentional.

Slow Play Ray

11-23-2005, 10:49 AM

[ QUOTE ]
dude, i grasped it too!!!

[/ QUOTE ]

my bad.

fnord_too

11-23-2005, 10:49 AM

[ QUOTE ]
The problem with this scenario is that the drive isn't created by the wheels, so this belt wouldn't result in the plane not moving, it would mean the wheels would be moving REALLY quickly, but the thrust would still push teh plane forward.

This scenario is impossible.

[/ QUOTE ]

Yeah, the exact speed I think will be determined by the friction in the axels given that the wheels are not skidding in any way. It's hard to picture the forces in my head on this one, so I am not sure if there can even be any force acting on the plane to counter the force of the thrust, but I don't know that it is impossible. I was assuming it was possible since I was reading it as a given.

Slow Play Ray

11-23-2005, 10:54 AM

[ QUOTE ]
[ QUOTE ]
The problem with this scenario is that the drive isn't created by the wheels, so this belt wouldn't result in the plane not moving, it would mean the wheels would be moving REALLY quickly, but the thrust would still push teh plane forward.

This scenario is impossible.

[/ QUOTE ]

Yeah, the exact speed I think will be determined by the friction in the axels given that the wheels are not skidding in any way.

[/ QUOTE ]

I was thinking about this earlier, too. I think the wheel speed/conveyor speed would basically accelerate exponentially until the plane took off. Clearly this whole scenario is probably not physically possible, but it's an interesting theory to discuss.

fnord_too

11-23-2005, 10:55 AM

[ QUOTE ]
[ QUOTE ]
The discussion in this thread makes me think perhaps your phrasing is awkward.

[/ QUOTE ]

I think everyone here understands what makes a plane lift. The question is - can lift be created in this scenario?

My wording was intentional.

[/ QUOTE ]

So your basic question is "Is there a physical contradiction in the assumptions"? Thinking about it more, I think there is since you assume the wheels roll freely (i.e. no skidding). Angular momentum isn't a factor since those vectors will be perependicular to the direction of the plane.

CrazyEyez

11-23-2005, 10:55 AM

This scenario is no different than if there was no conveyor runway but instead the breaks were locked on or the wheels were blocked. Sure there is some lift but not enough to take off.

Slow Play Ray

11-23-2005, 10:58 AM

[ QUOTE ]
This scenario is no different than if there was no conveyor runway but instead the breaks were locked on or the wheels were blocked. Sure there is some lift but not enough to take off.

[/ QUOTE ]

No - it's actually more like if the wheels were locked, but the runway was basically frictionless. Or even better - if the plane had no wheels and was just able to hover in the air. And it can certainly take off in those scenarios, right?

11-23-2005, 11:01 AM

[ QUOTE ]
[ QUOTE ]
The discussion in this thread makes me think perhaps your phrasing is awkward.

[/ QUOTE ]

I think everyone here understands what makes a plane lift. The question is - can lift be created in this scenario?

My wording was intentional.

[/ QUOTE ]

The question fundamentally is what force is imparted on the aircraft by the conveyor-runway. You are saying that that force is less than the force of the props (are you saying that it is 0?). I don't see how that could be the case from a standing start, but I'm not an engineer.

IndieMatty

11-23-2005, 11:05 AM

One would think that reading a thread like this, where a riddle is being solved involving such things as physics/math etc would not make me dumber than I already was.

Thanks Ray!

BOTW

11-23-2005, 11:05 AM

The plane will take off on a frictionless runway. It will not take off on the conveyor system.

Wheels reduce friction; your conveyor system, in essence, removes the wheels.

CrazyEyez

11-23-2005, 11:11 AM

[ QUOTE ]
[ QUOTE ]
This scenario is no different than if there was no conveyor runway but instead the breaks were locked on or the wheels were blocked. Sure there is some lift but not enough to take off.

[/ QUOTE ]

No - it's actually more like if the wheels were locked, but the runway was basically frictionless. Or even better - if the plane had no wheels and was just able to hover in the air. And it can certainly take off in those scenarios, right?

[/ QUOTE ]
Yes, but I don't see how your original scenario is the same as these last scenarios. I'll go back and reread it. But per your OP, if the plane moves forward through the air, and the wheels are still in contact with the conveyor, then the wheels and conveyor can't be going the same speed, as I see it.

daryn

11-23-2005, 11:11 AM

http://www.dartmouth.edu/~physics/lecture_demo/images/mechanics/skateboard.l.jpg

when the fan is plugged in, what happens? will the skateboard move? provide reasoning!

CrazyEyez

11-23-2005, 11:14 AM

Damn you. My head is spinning now.

FouTight

11-23-2005, 11:15 AM

doubtful, that fan doesn't look very powerful.

if it did move, it would move backwards.

daryn

11-23-2005, 11:18 AM

[ QUOTE ]
doubtful, that fan doesn't look very powerful.

if it did move, it would move backwards.

[/ QUOTE ]

pretend it's powerful enough

Slow Play Ray

11-23-2005, 11:19 AM

[ QUOTE ]
The plane will take off on a frictionless runway. It will not take off on the conveyor system.

Wheels reduce friction; your conveyor system, in essence, removes the wheels.

[/ QUOTE ]

So then why won't it take off on my conveyor system???

And for simplicity's sake, please neglect the bearing friction and wheel slip for this problem. In other words, just assume that the wheels can keep up with the conveyor at any speed, and vice versa.

IndieMatty

11-23-2005, 11:20 AM

[ QUOTE ]
[ QUOTE ]
doubtful, that fan doesn't look very powerful.

if it did move, it would move backwards.

[/ QUOTE ]

pretend it's powerful enough

[/ QUOTE ]

Can we pretend it runs on batterys too?

mostsmooth

11-23-2005, 11:21 AM

[ QUOTE ]
[ QUOTE ]
doubtful, that fan doesn't look very powerful.

if it did move, it would move backwards.

[/ QUOTE ]

pretend it's powerful enough

[/ QUOTE ]
i have zero college training, but the forces should balance, no? no movement of the skateboard (assuming the sail and fan are secured to the board)

TheWorstPlayer

11-23-2005, 11:22 AM

I have seen this contraption work.

Slow Play Ray

11-23-2005, 11:23 AM

In a perfect world, that contraption should stand perfectly still, no?

P.S. Damn thread hijacker - not everyone understand the plane problem yet!

daryn

11-23-2005, 11:24 AM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
doubtful, that fan doesn't look very powerful.

if it did move, it would move backwards.

[/ QUOTE ]

pretend it's powerful enough

[/ QUOTE ]

Can we pretend it runs on batterys too?

[/ QUOTE ]

yes, whatever

IndieMatty

11-23-2005, 11:24 AM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
doubtful, that fan doesn't look very powerful.

if it did move, it would move backwards.

[/ QUOTE ]

pretend it's powerful enough

[/ QUOTE ]
i have zero college training, but the forces should balance, no? no movement of the skateboard (assuming the sail and fan are secured to the board)

[/ QUOTE ]

I can't believe you're seriously answering this. It's plugged into a friggin outlet. It's not going anywhere. Holy [censored]!

MelK

11-23-2005, 11:26 AM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
doubtful, that fan doesn't look very powerful.

if it did move, it would move backwards.

[/ QUOTE ]

pretend it's powerful enough

[/ QUOTE ]
i have zero college training, but the forces should balance, no? no movement of the skateboard (assuming the sail and fan are secured to the board)

[/ QUOTE ]

Don't think of the sail as an opposing force, but rather as a redirecting force.

If you blow into your cupped hands, you are redirecting the wind, not canceling it.

mostsmooth

11-23-2005, 11:26 AM

[ QUOTE ]
your conveyor system, in essence, removes the wheels.

[/ QUOTE ]
this is not right
youre right the wheels purpose is to remove friction, but the axles dont care how fast or slow the wheels spin, and the plane is essentially floating. now all you need is some thrust

MelK

11-23-2005, 11:27 AM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
doubtful, that fan doesn't look very powerful.

if it did move, it would move backwards.

[/ QUOTE ]

pretend it's powerful enough

[/ QUOTE ]
i have zero college training, but the forces should balance, no? no movement of the skateboard (assuming the sail and fan are secured to the board)

[/ QUOTE ]

I can't believe you're seriously answering this. It's plugged into a friggin outlet. It's not going anywhere. Holy [censored]!

[/ QUOTE ]

The question was "will it move?", not "how far will it move?"

Eurotrash

11-23-2005, 11:27 AM

[ QUOTE ]
In a perfect world, that contraption should stand perfectly still, no?

P.S. Damn thread hijacker - not everyone understand the plane problem yet!

[/ QUOTE ]

this entire thread is making me wish I paid more attention in the fluid mechanics course I took. I think now that your OP has been reworded, Ray, that I understand what the situation you're actually describing is

Slow Play Ray

11-23-2005, 11:28 AM

[ QUOTE ]
[ QUOTE ]
your conveyor system, in essence, removes the wheels.

[/ QUOTE ]
this is not right
youre right the wheels purpose is to remove friction, but the axles dont care how fast or slow the wheels spin, and the plane is essentially floating. now all you need is some thrust

[/ QUOTE ]

Ah, I misunderstood what he meant by "removes the wheels" - this is correct.

Slow Play Ray

11-23-2005, 11:31 AM

[ QUOTE ]
I think now that your OP has been reworded, Ray, that I understand what the situation you're actually describing is

[/ QUOTE ]

/images/graemlins/confused.gif I didn't reword the OP at all - I only generalized that it could be basically any kind of plane, and specified there is no wind.

IndieMatty

11-23-2005, 11:34 AM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
doubtful, that fan doesn't look very powerful.

if it did move, it would move backwards.

[/ QUOTE ]

pretend it's powerful enough

[/ QUOTE ]
i have zero college training, but the forces should balance, no? no movement of the skateboard (assuming the sail and fan are secured to the board)

[/ QUOTE ]

I can't believe you're seriously answering this. It's plugged into a friggin outlet. It's not going anywhere. Holy [censored]!

[/ QUOTE ]

The question was "will it move?", not "how far will it move?"

[/ QUOTE ]

/images/graemlins/crazy.gif I suck at smart kid threads. Im out of here.

Eurotrash

11-23-2005, 11:35 AM

[ QUOTE ]
[ QUOTE ]
I think now that your OP has been reworded, Ray, that I understand what the situation you're actually describing is

[/ QUOTE ]

/images/graemlins/confused.gif I didn't reword the OP at all - I only generalized that it could be basically any kind of plane, and specified there is no wind.

[/ QUOTE ]

well, I should have said that when your original situation was reworded by somebody in the thread (I just revisited this thread after not checking it for a while.) somebody likened the wheels on the conveyor belt to a removal of friction, which now makes a lot more sense. I'm not sure why I didn't think of it that way initially

Patrick del Poker Grande

11-23-2005, 11:43 AM

I haven't read any of this, but I can tell just from the number of replies that there's some stupid [censored] going on. I have two questions.

First, are we assuming a no-slip condition between the wheels and the treadmill runway?

Second, is the treadmill runway itself at rest relative to ground, or is it somehow zooming a hundred miles an hour along the ground?

jon_1van

11-23-2005, 11:45 AM

[ QUOTE ]

http://www.dartmouth.edu/~physics/lecture_demo/images/mechanics/skateboard.l.jpg

when the fan is plugged in, what happens? will the skateboard move? provide reasoning!

[/ QUOTE ]

The fan pushes a bunch of air to the left. And hense the fan wants to more right. But since the paper doesn't catch all of the moving air's energy (air moving left because of fan) the system is unbalanced. The skateboard moves right.

Slow Play Ray

11-23-2005, 11:48 AM

[ QUOTE ]
First, are we assuming a no-slip condition between the wheels and the treadmill?

Second, is the treadmill itself at rest relative to ground, or is it somehow zooming a hundred miles an hour along the ground?

[/ QUOTE ]

Yes - no slip, as well as perfect bearings all around.

The treadmill mechanism itself it not moving relative to the ground, the conveyor part is. Just picture a moving walkway like in an airport, but much bigger (and faster).

fnord_too

11-23-2005, 11:50 AM

If it moves, it will be backwards since not all of the momentum from the air being forced forward will be imparted to the board.

Hiding

11-23-2005, 11:54 AM

Equal and opposite reactions, the pressure on the board and the pressure on the fan are equal, in an ideal situation, so no motion.

If the planes wheels can't slip and the conveyor structure is motionless, with respect to the plane and air flow then there is no lift.

If a truck driver has a load of chickens at a weigh station and beats on all the cages so the chickens are flying at the moment he is weighed, does the truck weigh less?

BOTW

11-23-2005, 11:54 AM

A plane is stuck to the ground cuz gravity is pushing down on it.
To lift the plane, we need airspeed.
There is no wind so airspeed = ground speed.
To get ground speed, we need to move forward compared to the ground.
We apply thrust to the plane.
Relative to the wheels contact on the conveyor, the plane moves forward, so the wheels start spinning.
However, our conveyor spins beneath our wheels at the exact speed our wheels turn.
Hence, if the conveyor itself isn't moving, the plane isn't moving and we have no ground speed.

Patrick del Poker Grande

11-23-2005, 11:56 AM

The plane can take off. The wheels and runway will accelerate like a mofo as it does. The wheels have nothing to do with the lift. The wheels do nothing for the plane other than provide a minimum altitude relative to the ground.

fnord_too

11-23-2005, 11:57 AM

[ QUOTE ]
A plane is stuck to the ground cuz gravity is pushing down on it.
To lift the plane, we need airspeed.
There is no wind so airspeed = ground speed.
To get ground speed, we need to move forward compared to the ground.
We apply thrust to the plane.
Relative to the wheels contact on the conveyor, the plane moves forward, so the wheels start spinning.
However, our conveyor spins beneath our wheels at the exact speed our wheels turn.
Hence, if the conveyor itself isn't moving, the plane isn't moving and we have no ground speed.

[/ QUOTE ]

The props/jet are creating a force on the plan. How does the conveyor create an opposte force if the wheels don't skid? That is the crux of the problem.

Hiding

11-23-2005, 12:00 PM

[ QUOTE ]
The plane can take off. The wheels and runway will accelerate like a mofo as it does. The wheels have nothing to do with the lift.

[/ QUOTE ]

At what point does airflow start over the wings? No props, use a jet.

Slow Play Ray

11-23-2005, 12:01 PM

[ QUOTE ]
Hence, if the conveyor itself isn't moving, the plane isn't moving and we have no ground speed.

[/ QUOTE ]

You were doing good right up until this part.

Patrick del Poker Grande

11-23-2005, 12:01 PM

Alright, kids. I'm going to let you in on a little rocket science secret. Prop planes do not generate lift by blowing air over the wings.

4_2_it

11-23-2005, 12:04 PM

[ QUOTE ]
Alright, kids. I'm going to let you in on a little rocket science secret. Prop planes do not generate lift by blowing air over the wings.

[/ QUOTE ]

Yea right! Next you are going to tell me that Santa Claus and the Easter Bunny don't exist.

Patrick del Poker Grande

11-23-2005, 12:06 PM

I suggest everyone draw a Free Body Diagram. Use MS Paint - it'll be fun.

Slow Play Ray

11-23-2005, 12:06 PM

[ QUOTE ]
At what point does airflow start over the wings? No props, use a jet.

[/ QUOTE ]

It starts as soon as the plane starts moving.

And why would it matter if its props or jet??

Slow Play Ray

11-23-2005, 12:07 PM

[ QUOTE ]
Alright, kids. I'm going to let you in on a little rocket science secret. Prop planes do not generate lift by blowing air over the wings.

[/ QUOTE ]

way to take half the fun out of this thread!

kevyk

11-23-2005, 12:07 PM

If you are saying that the runway moves backward at the speed the wheels’ center of mass translates forward, the plane is not moving forward with respect to the air, and will never take off.

If the runway moves backward at the tangential speed at which the edge of the wheels move, then the plane can achieve forward movement with respect to the air, and presumably take off.

The plane moves a distance d equal to the circumference of its wheels in time t. The time t is the period of rotation of the plane’s wheels, which is equal to 1/w, the angular speed of the wheels’ rotation.

Vplane=(2*pi*rwheel)*w

Omega is equal to the speed of the edge of the wheel divided by their radius by geometry.

Vedge=rwheel*w

Thus, Vplane=2*pi*Vedge.

So the plane speed with respect to the air = Vplane-Vrunway = Vplane-Vplane/(2*pi) = Vplane*(1-1/(2*pi)). (Vplane is the speed of the plane with respect to the runway...)

Eurotrash

11-23-2005, 12:08 PM

[ QUOTE ]
I suggest everyone draw a Free Body Diagram. Use MS Paint - it'll be fun.

[/ QUOTE ]

oh, sweet. I was going to suggest drawing free body diagrams earlier in the thread. I don't know if I'm up for the challenge at this point, though

Slow Play Ray

11-23-2005, 12:11 PM

Patrick del Poker Grande

11-23-2005, 12:12 PM

[ QUOTE ]
If you are saying that the runway moves backward at the speed the wheels’ center of mass translates forward, the plane is not moving forward with respect to the air, and will never take off.

If the runway moves backward at the tangential speed at which the edge of the wheels move, then the plane can achieve forward movement with respect to the air, and presumably take off.

The plane moves a distance d equal to the circumference of its wheels in time t. The time t is the period of rotation of the plane’s wheels, which is equal to 1/w, the angular speed of the wheels’ rotation.

Vplane=(2*pi*rwheel)*w

Omega is equal to the speed of the edge of the wheel divided by their radius by geometry.

Vedge=rwheel*w

Thus, Vplane=2*pi*Vedge.

So the plane speed with respect to the air = Vplane-Vrunway = Vplane-Vplane/(2*pi) = Vplane*(1-1/(2*pi)). (Vplane is the speed of the plane with respect to the runway...)

[/ QUOTE ]
I hope you had fun doing all this crap.

Patrick del Poker Grande

11-23-2005, 12:12 PM

[ QUOTE ]
[ QUOTE ]
Alright, kids. I'm going to let you in on a little rocket science secret. Prop planes do not generate lift by blowing air over the wings.

[/ QUOTE ]

way to take half the fun out of this thread!

[/ QUOTE ]
Nah, I just shifted the fun. MS Paint is fun!

4_2_it

11-23-2005, 12:14 PM

Is this a pre-lude to a Coanda vs. Bernouilli effect argument? I am not a scientist, but will amke an attempt to answer your question, the Coanda effect causes the air that moves over the wing is deflected downward and creates lift. I don't see how a conveyor belt can prevent this from occurring.

Patrick del Poker Grande

11-23-2005, 12:17 PM

[ QUOTE ]
Is this a pre-lude to a Coanda vs. Bernouilli effect argument? I am not a scientist, but will amke an attempt to answer your question, the Coanda effect causes the air that moves over the wing is deflected downward and creates lift. I don't see how a conveyor belt can prevent this from occurring.

[/ QUOTE ]
No. Go hit MS Paint like everyone else is right now.

BoogerFace

11-23-2005, 12:26 PM

http://img194.imageshack.us/img194/5650/oot2qv.jpg

Eurotrash

11-23-2005, 12:35 PM

Ok, so far I have this, Patrick. note that you are riding on top of the plane.

edit: i suppose I shouldnt have included the tangential velocity of the wheel, i don't really know. but i threw it in there for some reason anyway. deal with it.

http://img455.imageshack.us/img455/8931/plane8wy.jpg

Patrick del Poker Grande

11-23-2005, 12:37 PM

[ QUOTE ]
Ok, so far I have this, Patrick. note that you are riding on top of the plane.

http://img455.imageshack.us/img455/8931/plane8wy.jpg

[/ QUOTE ]
Very nice. That's a good start.

IndieMatty

11-23-2005, 12:38 PM

im crying. this is awesome.

Eurotrash

11-23-2005, 12:39 PM

[ QUOTE ]
im crying. this is awesome.

[/ QUOTE ]

this is just the beginning my friend. it gets better!

razor

11-23-2005, 12:45 PM

[ QUOTE ]
Prop planes do not generate lift by blowing air over the wings.

[/ QUOTE ]

/images/graemlins/shocked.gif

Voltron87

11-23-2005, 12:52 PM

[ QUOTE ]
gravity lol

[/ QUOTE ]

so good.

how is this that complicated though? the plane is not going to take off. the conveyor will push it backwards with the same force that the wheels push it forward, and the plane will stay stationary relative to the ground. and LMAO to the person who thought the propellors were the source of the air that blows over the wings. AWESOME. i got a 1 on the ap C physics test, so maybe I am a physics idiot. but that was for lack of effort not intellegince.

daryn

11-23-2005, 12:55 PM

this is the problem with these threads.. you get people saying

"how is this that complicated? the ...." and then they just go on to list a ton of incorrect assumptions.

codewarrior

11-23-2005, 12:55 PM

I can't believe this thread got this long.

I'm going on my gut instinct upon my first reading of the OP.

There is thrust, but no air flow being generated, therefore no lift. Therefore, no, it ain't taking off.

Patrick del Poker Grande

11-23-2005, 12:55 PM

[ QUOTE ]
[ QUOTE ]
gravity lol

[/ QUOTE ]

so good.

how is this that complicated though? the plane is not going to take off. the conveyor will push it backwards with the same force that the wheels push it forward, and the plane will stay stationary relative to the ground. and LMAO to the person who thought the propellors were the source of the air that blows over the wings. AWESOME. i got a 1 on the ap C physics test, so maybe I am a physics idiot. but that was for lack of effort not intellegince.

[/ QUOTE ]
No. <font color=" white">You need to re-think the source of thrust. This isn't a car.</font>

Patrick del Poker Grande

11-23-2005, 12:57 PM

[ QUOTE ]
this is the fun with these threads.. you get people saying

"how is this that complicated? the ...." and then they just go on to list a ton of incorrect assumptions.

[/ QUOTE ]

Voltron87

11-23-2005, 12:58 PM

ok, is this because the wheels have no friction to push forward or something? or is the answer somewhere back in the thread. i just assumed that the force to the left would be equal to the force to the right and it would be stationary and not lift off.

Eurotrash

11-23-2005, 12:58 PM

um, a brief update I guess.

http://img399.imageshack.us/img399/1418/plane8oz.jpg

Vavavoom

11-23-2005, 12:58 PM

[ QUOTE ]
um, a brief update I guess.

http://img399.imageshack.us/img399/1418/plane8oz.jpg

[/ QUOTE ]

I THINK I LOVE OOT !!!!

Patrick del Poker Grande

11-23-2005, 12:59 PM

[ QUOTE ]
um, a brief update I guess.

http://img399.imageshack.us/img399/1418/plane8oz.jpg

[/ QUOTE ]
BIMO. 5 Stars!

BOTW

11-23-2005, 01:14 PM

I assumed the conveyor would be just like sticking the plane on a dynamometer and the plane would never be able to move forward. I was wrong. What you're describing is more like a Harrier or frictionless runway.
http://img410.imageshack.us/img410/2661/rayharrier1ey.jpg
Or maybe the conveyor ramps up to infinite speed and the universe collapses?

Slow Play Ray

11-23-2005, 01:18 PM

This thread is moving in a brilliant direction I never foresaw.

And the beautiful part is, people are still chiming in with the wrong answer to the OP. /images/graemlins/grin.gif

Patrick del Poker Grande

11-23-2005, 01:20 PM

[ QUOTE ]
Or maybe the conveyor ramps up to infinite speed and the universe collapses?

[/ QUOTE ]
You can use kevyk's work to figure out the speed of the wheels and conveyor... how do I say this without giving it away... no, that's all. However, this still has nothing to do with the plane's ability to take off, given the parameters here.

mmbt0ne

11-23-2005, 01:24 PM

[ QUOTE ]
[ QUOTE ]
gravity lol

[/ QUOTE ]

so good.

how is this that complicated though? the plane is not going to take off. the conveyor will push it backwards with the same force that the wheels push it forward, and the plane will stay stationary relative to the ground. and LMAO to the person who thought the propellors were the source of the air that blows over the wings. AWESOME. i got a 1 on the ap C physics test, so maybe I am a physics idiot. but that was for lack of effort not intellegince.

[/ QUOTE ]

I love when people say this. It's like a foolproof excuse for being afraid of trying and failing.

kevyk

11-23-2005, 01:29 PM

Yeah, except I realized right after I posted that I made a big mistake...

Namely, the speed of the wheel where it touches the ground is zero if there is no slipping. Duh...in that case you've got no treadmill-runway at all.

In any case it doesn't matter. The moving runway doesn't exert any force on the plane, so the engines will accelerate it to normal airspeed and it will take off. The wheels will just spin faster than they would otherwise.

Voltron87

11-23-2005, 01:32 PM

I got a 5 on BC calc, im not just making it up. i have tons of evidence to say that im a smart person.

and yes, intelligence was spelled incorrectly on purpose.

mmbt0ne

11-23-2005, 01:37 PM

[ QUOTE ]
I got a 5 on BC calc, im not just making it up. i have tons of evidence to say that im a smart person.

[/ QUOTE ]

You can be great at one thing, but not at another. I'm not saying you aren't smart overall, you've made sure to make that fact clear many times before /images/graemlins/tongue.gif, just that your excuse for your physics grade is weak at best.

[ QUOTE ]

and yes, intelligence was spelled incorrectly on purpose.

[/ QUOTE ]

I didn't even notice. Of course, I only got a 1 on my AP English exam, but that's because I didn't try. /images/graemlins/smile.gif

Patrick del Poker Grande

11-23-2005, 01:38 PM

[ QUOTE ]
[ QUOTE ]
I got a 5 on BC calc, im not just making it up. i have tons of evidence to say that im a smart person.

[/ QUOTE ]

You can be great at one thing, but not at another. I'm not saying you aren't smart overall, you've made sure to make that fact clear many times before /images/graemlins/tongue.gif, just that your excuse for your physics grade is weak at best.

[ QUOTE ]

and yes, intelligence was spelled incorrectly on purpose.

[/ QUOTE ]

I didn't even notice. Of course, I only got a 1 on my AP English exam, but that's because I didn't try. /images/graemlins/smile.gif

[/ QUOTE ]
How'd you two bitches do on your AP art exam? Get some MS Paint!

Eurotrash

11-23-2005, 01:42 PM

ok, I think I'm still missing some stuff, but I tried to be as thorough as possible. I demand a lot of partial credit for showing formulas

http://img474.imageshack.us/img474/6564/plane4vg.jpg

LetYouDown

11-23-2005, 01:43 PM

[ QUOTE ]
opposite direction of the plane

[/ QUOTE ]
Define "opposite" if the plane isn't moving.

Patrick del Poker Grande

11-23-2005, 01:44 PM

Alright, now what if it's a jet?

mmbt0ne

11-23-2005, 01:45 PM

[ QUOTE ]
Alright, now what if it's a jet?

[/ QUOTE ]

The owl better stay in the cockpit.

Patrick del Poker Grande

11-23-2005, 01:45 PM

[ QUOTE ]
[ QUOTE ]
opposite direction of the plane

[/ QUOTE ]
Define "opposite" if the plane isn't moving.

[/ QUOTE ]
Oohh! I think you're on to something!

Senor Cardgage

11-23-2005, 01:46 PM

How bout some normal forces up in this!

Slow Play Ray

11-23-2005, 01:47 PM

[ QUOTE ]
[ QUOTE ]
opposite direction of the plane

[/ QUOTE ]
Define "opposite" if the plane isn't moving.

[/ QUOTE ]

no.

Eurotrash

11-23-2005, 01:47 PM

[ QUOTE ]
Alright, now what if it's a jet?

[/ QUOTE ]

/images/graemlins/frown.gif

i've got no more ideas right now. i poured my heart and soul into that diagram.

DaffyDuck

11-23-2005, 01:51 PM

The proposed scenario is physically impossible. As soon as the plane starts to move forward relative to the ground by thrusting with it's props or jets, the wheels will move faster than the conveyor belt.

If the conveyor tries to speed up to compensate for this then the wheels, which are touching the conveyor belt, will also speed up, up to infinity, and maintain their relative speed compared to the conveyor. So, if the plane is moving forward 200 MPH relative to the ground, it's wheels will always move 200 MPH faster than the conveyor belt.

Bob

Patrick del Poker Grande

11-23-2005, 01:53 PM

[ QUOTE ]
The proposed scenario is physically impossible. As soon as the plane starts to move forward relative to the ground by thrusting with it's props or jets, the wheels will move faster than the conveyor belt.

If the conveyor tries to speed up to compensate for this then the wheels, which are touching the conveyor belt, will also speed up, up to infinity, and maintain their relative speed compared to the conveyor. So, if the plane is moving forward 200 MPH relative to the ground, it's wheels will always move 200 MPH faster than the conveyor belt.

Bob

[/ QUOTE ]
This is at the same time both the most wrong and the most right (outside of Ray, blinden84, and myself) I've seen anybody be in this thread.

IndieMatty

11-23-2005, 02:00 PM

[ QUOTE ]
ok, I think I'm still missing some stuff, but I tried to be as thorough as possible. I demand a lot of partial credit for showing formulas

http://img474.imageshack.us/img474/6564/plane4vg.jpg

[/ QUOTE ]

wow where is the 10 star option?

elwoodblues

11-23-2005, 02:07 PM

Is this really any different than asking if a plane can take off on a sheet of ice (or something frictionless)? If I'm standing on roller skates on a treadmill (which I do often) and somebody pushes me forward I'm still going to move forward, just as the plane will still move forward because the props are propelling it forward --- the wheels seem irrelevant.

Patrick del Poker Grande

11-23-2005, 02:09 PM

[ QUOTE ]
Is this really any different than asking if a plane can take off on a sheet of ice (or something frictionless)?

[/ QUOTE ]
Well, the wheels do help keep it from sliding sideways and from yawing.

daryn

11-23-2005, 02:12 PM

[ QUOTE ]
[ QUOTE ]
ok, I think I'm still missing some stuff, but I tried to be as thorough as possible. I demand a lot of partial credit for showing formulas

http://img474.imageshack.us/img474/6564/plane4vg.jpg

[/ QUOTE ]

wow where is the 10 star option?

[/ QUOTE ]

baaaahahahahahhaha

Slow Play Ray

11-23-2005, 02:13 PM

[ QUOTE ]
Is this really any different than asking if a plane can take off on a sheet of ice (or something frictionless)?

[/ QUOTE ]

Only in the sense that it is far more confusing for those who cannot separate wheel velocity from plane velocity in their minds! /images/graemlins/grin.gif

Patrick del Poker Grande

11-23-2005, 02:14 PM

NLSoldier

11-23-2005, 02:21 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Is this really any different than asking if a plane can take off on a sheet of ice (or something frictionless)?

[/ QUOTE ]

Only in the sense that it is far more confusing for those who cannot separate wheel velocity from plane velocity in their minds! /images/graemlins/grin.gif

[/ QUOTE ]
This ought to blow someone's mind: The wheels could be spinning backward and it wouldn't matter!

[/ QUOTE ]

yeah it def. blew my mind. now give the answer plz? and the answer to daryns skateboard thing too. me and my friend have a bet on both.

Slow Play Ray

11-23-2005, 02:22 PM

[ QUOTE ]
yeah it def. blew my mind. now give the answer plz? and the answer to daryns skateboard thing too. me and my friend have a bet on both.

[/ QUOTE ]

The plane can take off - this has already been established.

For Darryn's - as pictured, the skateboard would go backwards. If it were a perfect sail instead of that board, it would stand still.

fnord_too

11-23-2005, 02:23 PM

[ QUOTE ]
[ QUOTE ]
yeah it def. blew my mind. now give the answer plz? and the answer to daryns skateboard thing too. me and my friend have a bet on both.

[/ QUOTE ]

The plane can take off - this has already been established.

[/ QUOTE ]

I thought we determined it was a physically impossible scenario (contradicting assumptions)

NLSoldier

11-23-2005, 02:25 PM

[ QUOTE ]
[ QUOTE ]
yeah it def. blew my mind. now give the answer plz? and the answer to daryns skateboard thing too. me and my friend have a bet on both.

[/ QUOTE ]

The plane can take off - this has already been established.

For Darryn's - as pictured, the skateboard would go backwards. If it were a perfect sail instead of that board, it would stand still.

[/ QUOTE ]

when was it established?

Slow Play Ray

11-23-2005, 02:26 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
yeah it def. blew my mind. now give the answer plz? and the answer to daryns skateboard thing too. me and my friend have a bet on both.

[/ QUOTE ]

The plane can take off - this has already been established.

[/ QUOTE ]

I thought we determined it was a physically impossible scenario (contradicting assumptions)

[/ QUOTE ]

Huh? Noone thinks you can actually build such a contraption, but theoretically it could take off.

What contradicting assumptions are you speaking of?

Slow Play Ray

11-23-2005, 02:26 PM

[ QUOTE ]
when was it established?

[/ QUOTE ]

Patrick's original response was the cleanest answer:

[ QUOTE ]
The plane can take off. The wheels and runway will accelerate like a mofo as it does.

[/ QUOTE ]

CrazyEyez

11-23-2005, 02:27 PM

[ QUOTE ]
Is this really any different than asking if a plane can take off on a sheet of ice (or something frictionless)? If I'm standing on roller skates on a treadmill (which I do often) and somebody pushes me forward I'm still going to move forward, just as the plane will still move forward because the props are propelling it forward --- the wheels seem irrelevant.

[/ QUOTE ]
Yeah except that if the plane is moving forward then the wheels can't be going the same speed as the conveyor so the original conditions are not met.

I fullyadmit I'm wrong about this, but I don't understand why. How long do we have to wait until one of the people who "gets it" tries to offer a clear explanation instead of a "You are wrong - do you see why?"
In each of the analogies mentioned for why the plane can take off, I fail to see how the original conditions of the wheels and conveyor moving at the same speed are met. Even though intuitively I believe the wheels should be irrelevant to the problem.

11-23-2005, 02:34 PM

Wow. This thread is brilliant! How is it possible that only 3 or 4 people in this thread actually understand the answer to this question?

The answer has already been given in this thread a couple of times but here's a hint, how do you think rockets take off if they have no wings?

Patrick del Poker Grande

11-23-2005, 02:37 PM

I could give the answer, but that would kill the thread and we don't have enough MS Paint yet. Eurotrash has been brilliant so far... I'm waiting for more entries.

NLSoldier

11-23-2005, 02:38 PM

[ QUOTE ]
how do you think rockets take off if they have no wings?

[/ QUOTE ]

the rocket thrust is downward...

NLSoldier

11-23-2005, 02:41 PM

[ QUOTE ]
I could give the answer, but that would kill the thread and we don't have enough MS Paint yet. Eurotrash has been brilliant so far... I'm waiting for more entries.

[/ QUOTE ]

ppl are claiming you already gave it...which it appears you did.

can you just PM the answer with a short explanation that will settle it so my friend will buy my lunch?

edit-ok now its lunch+$400

LetYouDown

11-23-2005, 02:41 PM

[ QUOTE ]
I fail to see how the original conditions of the wheels and conveyor moving at the same speed are met

[/ QUOTE ]
It's a matter of relative speed. As the plane moves forward, the conveyor belt (in a relative way) is moving faster. I've come to the conclusion that the plane will accelerate and take off as well. The wheels are not completely separate from the engine in the case of a plane, as opposed to cars where they are attached to an axle that moves.

daryn

11-23-2005, 02:42 PM

[ QUOTE ]
[ QUOTE ]
yeah it def. blew my mind. now give the answer plz? and the answer to daryns skateboard thing too. me and my friend have a bet on both.

[/ QUOTE ]

The plane can take off - this has already been established.

For Darryn's - as pictured, the skateboard would go backwards. If it were a perfect sail instead of that board, it would stand still.

[/ QUOTE ]

describe a perfect sail

11-23-2005, 02:42 PM

[ QUOTE ]
[ QUOTE ]
Is this really any different than asking if a plane can take off on a sheet of ice (or something frictionless)?

[/ QUOTE ]

Only in the sense that it is far more confusing for those who cannot separate wheel velocity from plane velocity in their minds! /images/graemlins/grin.gif

[/ QUOTE ]

You realize that in your OP, wheel speed = anything, plane speed = 0.

Obv, if the plane isn't moving forward relative to the air, it doesn't take off.

Unless, of course, your plan was to phrase a question with a clear answer, then try to confuse people so you would have a big thread.

CrazyEyez

11-23-2005, 02:43 PM

[ QUOTE ]
Wow. This thread is brilliant! How is it possible that only 3 or 4 people in this thread actually understand the answer to this question?

The answer has already been given in this thread a couple of times but here's a hint, how do you think rockets take off if they have no wings?

[/ QUOTE ]
I'm fully admitting I'm stupid because I can't understand the OP, but I'm pretty positive your rocket analogy doesn't apply here. The plane doesn't have rocket engines and they aren't aimed downward.

Patrick del Poker Grande

11-23-2005, 02:45 PM

[ QUOTE ]
[ QUOTE ]
Wow. This thread is brilliant! How is it possible that only 3 or 4 people in this thread actually understand the answer to this question?

The answer has already been given in this thread a couple of times but here's a hint, how do you think rockets take off if they have no wings?

[/ QUOTE ]
I'm fully admitting I'm stupid because I can't understand the OP, but I'm pretty positive your rocket analogy doesn't apply here. The plane doesn't have rocket engines and they aren't aimed downward.

[/ QUOTE ]
You know, there are rocket-propelled planes. Imagine that this plane is the Bell X-1 (first manned vehicle to break the sound barrier).

11-23-2005, 02:46 PM

[ QUOTE ]
Wow. This thread is brilliant! How is it possible that only 3 or 4 people in this thread actually understand the answer to this question?

The answer has already been given in this thread a couple of times but here's a hint, how do you think rockets take off if they have no wings?

[/ QUOTE ]

This is a great post for two reasons.

1. The tone of the post.
2. The way the author believes planes and rockets are the same, just tilted sideways, and goes so far as to say it's a "hint"

CrazyEyez

11-23-2005, 02:47 PM

[ QUOTE ]
I could give the answer, but that would kill the thread and we don't have enough MS Paint yet. Eurotrash has been brilliant so far... I'm waiting for more entries.

[/ QUOTE ]
Fine. I'm not giving up. I want to understand this.

The plane has to move forward to generate lift. I can't get my around how the plane can move forward while still maintaining wheel speed = conveyer speed. Give me a hint.

Patrick del Poker Grande

11-23-2005, 02:47 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Wow. This thread is brilliant! How is it possible that only 3 or 4 people in this thread actually understand the answer to this question?

The answer has already been given in this thread a couple of times but here's a hint, how do you think rockets take off if they have no wings?

[/ QUOTE ]
I'm fully admitting I'm stupid because I can't understand the OP, but I'm pretty positive your rocket analogy doesn't apply here. The plane doesn't have rocket engines and they aren't aimed downward.

[/ QUOTE ]
You know, there are rocket-propelled planes. Imagine that this plane is the Bell X-1 (first manned vehicle to break the sound barrier).

[/ QUOTE ]
I will agree, however, that the rocket analogy doesn't exactly apply here. It's not completely irrellevant, though.

CrazyEyez

11-23-2005, 02:48 PM

[ QUOTE ]
[ QUOTE ]
Wow. This thread is brilliant! How is it possible that only 3 or 4 people in this thread actually understand the answer to this question?

The answer has already been given in this thread a couple of times but here's a hint, how do you think rockets take off if they have no wings?

[/ QUOTE ]

This is a great post for two reasons.

1. The tone of the post.
2. The way the author believes planes and rockets are the same, just tilted sideways, and goes so far as to say it's a "hint"

[/ QUOTE ]

It is a hint and I never said they were the same.

4_2_it

11-23-2005, 02:48 PM

As long as the thrust of jet engines can overcome the drag of the conveyor belt then the plane will take off. Damn, I wish I could remember more from my high school physics class 20 years ago! Patrick, is one of Newton's Laws involved in this? I remember that seemed to be a theme in most high school physics exercises.

Patrick del Poker Grande

11-23-2005, 02:48 PM

[ QUOTE ]
[ QUOTE ]
I could give the answer, but that would kill the thread and we don't have enough MS Paint yet. Eurotrash has been brilliant so far... I'm waiting for more entries.

[/ QUOTE ]
Fine. I'm not giving up. I want to understand this.

The plane has to move forward to generate lift. I can't get my around how the plane can move forward while still maintaining wheel speed = conveyer speed. Give me a hint.

[/ QUOTE ]
I'm not sure what meaningful hint I can give you that wouldn't give away the explanation. I seriously suggest busting out a good free body diagram.

Eurotrash

11-23-2005, 02:50 PM

[ QUOTE ]
I'm not sure what meaningful hint I can give you that wouldn't give away the explanation. I seriously suggest busting out a good free body diagram.

[/ QUOTE ]

I'm surprised these simpletons still cannot grasp it despite the diagram I painstakingly laid out for them.

LetYouDown

11-23-2005, 02:51 PM

The key here is that the belt isn't able to prevent the plane from having forward motion. A car moves forward by applying energy to the ground, a plane moves forward by applying energy to the air. The wheels will spin significantly faster, but otherwise it will have no affect on the speed of the plane.

The interesting question to me at this point is if the brakes on the wheels are applied, what happens. Also, if the plane isn't using any thrust to move forward but the belt is moving backward, do the wheels just spin or does the entire plane move?

Slow Play Ray

11-23-2005, 02:52 PM

[ QUOTE ]
describe a perfect sail

[/ QUOTE ]

in this case, one big enough to catch all the wind from the fan and redirect the force with 100% efficiency.

BoogerFace

11-23-2005, 02:53 PM

[ QUOTE ]

Now you're just [censored]ing with us.

[/ QUOTE ]

Yeah - everybody knows that planes fly because of pixie dust.

Slow Play Ray

11-23-2005, 02:57 PM

[ QUOTE ]
You realize that in your OP, wheel speed = anything, plane speed = 0.

Obv, if the plane isn't moving forward relative to the air, it doesn't take off.

Unless, of course, your plan was to phrase a question with a clear answer, then try to confuse people so you would have a big thread.

[/ QUOTE ]

I've said this multiple times now - at no point in this thread did I say plane speed = zero.

I suggest following Patrick's advice and creating a FBD.

11-23-2005, 02:59 PM

hey, i dont post here often, but i do read OOT a bit, but this is the dumbest question ever; im the guy NLSoldier has a bet with.....i need a way to settle this bet......if anyone can help me out with this, it would be greatly appreciated; ive tried to explain the concept of lift, but he just doesnt get it

the only way a plane gets into the air is because of lift; its the only way....to get lift, you need wind over a wing, in this case there is wind, so no lift, so no takeoff

im an aerospace engineering student, and he wont take mine or anyone of my aerospace's buddies answer; please help me settle this! i got $400 on it

EDIT: ive offered to take a poll of 15 aerospace engineering professors, and even if one of them says the plane takes off, i would admit defeat...thoughts?

Stuey

11-23-2005, 02:59 PM

http://i2.photobucket.com/albums/y19/Stuey2plus2/second/HomerDreams1.gif

11-23-2005, 03:00 PM

[ QUOTE ]
im an aerospace engineering student

[/ QUOTE ]

not for long.

LetYouDown

11-23-2005, 03:01 PM

[ QUOTE ]
i had $400 on it

[/ QUOTE ]
FYP.

Patrick del Poker Grande

11-23-2005, 03:01 PM

[ QUOTE ]
The interesting question to me at this point is if the brakes on the wheels are applied, what happens. Also, if the plane isn't using any thrust to move forward but the belt is moving backward, do the wheels just spin or does the entire plane move?

[/ QUOTE ]
The answers to these questions all depend on your assumed friction coefficients, the exact workings of the conveyor, and assumptions about the plane's engines being strong enough to overcome these kinds of forces (which they probably are).

4_2_it

11-23-2005, 03:01 PM

[ QUOTE ]

http://img474.imageshack.us/img474/6564/plane4vg.jpg

[/ QUOTE ]

Why isn't El Diablo sitting in 1st Class?

Slow Play Ray

11-23-2005, 03:02 PM

a couple key words to think about:

thrust
accelerate

daryn

11-23-2005, 03:03 PM

[ QUOTE ]
Patrick, is one of Newton's Laws involved in this?

[/ QUOTE ]

"LOL"

Patrick del Poker Grande

11-23-2005, 03:04 PM

[ QUOTE ]
hey, i dont post here often, but i do read OOT a bit, but this is the dumbest question ever; im the guy NLSoldier has a bet with.....i need a way to settle this bet......if anyone can help me out with this, it would be greatly appreciated; ive tried to explain the concept of lift, but he just doesnt get it

the only way a plane gets into the air is because of lift; its the only way....to get lift, you need wind over a wing, in this case there is wind, so no lift, so no takeoff

im an aerospace engineering student, and he wont take mine or anyone of my aerospace's buddies answer; please help me settle this! i got $400 on it

[/ QUOTE ]
If it helps, I'm not sure NLSoldier is right, but you're wrong.

Patrick del Poker Grande

11-23-2005, 03:05 PM

[ QUOTE ]
EDIT: ive offered to take a poll of 15 aerospace engineering professors, and even if one of them says the plane takes off, i would admit defeat...thoughts?

[/ QUOTE ]
That's me. Pay up.

edit: I read fast and didn't see the word "professors".

Eurotrash

11-23-2005, 03:05 PM

[ QUOTE ]
Why isn't El Diablo sitting in 1st Class?

[/ QUOTE ]

it's obviously El Diablo's private jet. the entire cabin is extravagant

Patrick del Poker Grande

11-23-2005, 03:07 PM

[ QUOTE ]
[ QUOTE ]
Why isn't El Diablo sitting in 1st Class?

[/ QUOTE ]

it's obviously El Diablo's private jet. the entire cabin is extravagant

[/ QUOTE ]
Nice. I was going to suggest that he likes the exit row.

Senor Cardgage

11-23-2005, 03:07 PM

I had to think about this for like fifteen minutes before I realized how stupid I was.

Patrick, Ray, et al. are clearly correct. The rotation of the wheels doesn't have a damn thing to do with the plane's velocity.

daryn

11-23-2005, 03:07 PM

[ QUOTE ]
[ QUOTE ]
hey, i dont post here often, but i do read OOT a bit, but this is the dumbest question ever; im the guy NLSoldier has a bet with.....i need a way to settle this bet......if anyone can help me out with this, it would be greatly appreciated; ive tried to explain the concept of lift, but he just doesnt get it

the only way a plane gets into the air is because of lift; its the only way....to get lift, you need wind over a wing, in this case there is wind, so no lift, so no takeoff

im an aerospace engineering student, and he wont take mine or anyone of my aerospace's buddies answer; please help me settle this! i got $400 on it

[/ QUOTE ]
If it helps, I'm not sure NLSoldier is right, but you're wrong.

[/ QUOTE ]

after a brief convo on AIM, i have deduced that NLsoldier wins $400

CrazyEyez

11-23-2005, 03:11 PM

Tell me if this analogy makes sense:

I've got my daughter in a stroller going the wrong way on the moving walkway at the airport. I'm standing next to it on the ground, not on the walkway. I reach over and push the stroller hard enough that it moves forward relative to me. If the stroller had wings, there'd be lift. But at this point aren't the wheels moving faster than the walkway? Is this whole thing semantical?

Patrick del Poker Grande

11-23-2005, 03:11 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
hey, i dont post here often, but i do read OOT a bit, but this is the dumbest question ever; im the guy NLSoldier has a bet with.....i need a way to settle this bet......if anyone can help me out with this, it would be greatly appreciated; ive tried to explain the concept of lift, but he just doesnt get it

the only way a plane gets into the air is because of lift; its the only way....to get lift, you need wind over a wing, in this case there is wind, so no lift, so no takeoff

im an aerospace engineering student, and he wont take mine or anyone of my aerospace's buddies answer; please help me settle this! i got $400 on it

[/ QUOTE ]
If it helps, I'm not sure NLSoldier is right, but you're wrong.

[/ QUOTE ]

after a brief convo on AIM, i have deduced that NLsoldier wins $400

[/ QUOTE ]
And lunch too, right?

Eurotrash

11-23-2005, 03:12 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Why isn't El Diablo sitting in 1st Class?

[/ QUOTE ]

it's obviously El Diablo's private jet. the entire cabin is extravagant

[/ QUOTE ]
Nice. I was going to suggest that he likes the exit row.

[/ QUOTE ]

this could very well be why he chose that particular area of his jet to lounge in.

I have an urge to do more MS Paint.

11-23-2005, 03:13 PM

pat, the only upward force experienced on a plane when its taking off is lift, and to produce lift, you need wind over an airfoil, in this case theres no wind, thats the simplest explanation anyone can offer

11-23-2005, 03:13 PM

[ QUOTE ]
[ QUOTE ]
You realize that in your OP, wheel speed = anything, plane speed = 0.

Obv, if the plane isn't moving forward relative to the air, it doesn't take off.

Unless, of course, your plan was to phrase a question with a clear answer, then try to confuse people so you would have a big thread.

[/ QUOTE ]

I've said this multiple times now - at no point in this thread did I say plane speed = zero.

I suggest following Patrick's advice and creating a FBD.

[/ QUOTE ]

UHHHHHHHHHHH what is your point.

Either the conveyor belt is moving exactly opposite of the plane or it is not.

HOW is the plane moving? I would love to know, so I can throw my engineering degree in the trash.

Patrick del Poker Grande

11-23-2005, 03:13 PM

[ QUOTE ]
Tell me if this analogy makes sense:

I've got my daughter in a stroller going the wrong way on the moving walkway at the airport. I'm standing next to it on the ground, not on the walkway. I reach over and push the stroller hard enough that it moves forward relative to me. If the stroller had wings, there'd be lift. But at this point aren't the wheels moving faster than the walkway? Is this whole thing semantical?

[/ QUOTE ]
This is a good analogy. Go look at kevyk's post and you might be able to reconcile this.

11-23-2005, 03:14 PM

[ QUOTE ]
Tell me if this analogy makes sense:

[/ QUOTE ]
yes

[ QUOTE ]
Is this whole thing semantical?

[/ QUOTE ]

nope.

11-23-2005, 03:14 PM

[ QUOTE ]
[ QUOTE ]
hey, i dont post here often, but i do read OOT a bit, but this is the dumbest question ever; im the guy NLSoldier has a bet with.....i need a way to settle this bet......if anyone can help me out with this, it would be greatly appreciated; ive tried to explain the concept of lift, but he just doesnt get it

the only way a plane gets into the air is because of lift; its the only way....to get lift, you need wind over a wing, in this case there is wind, so no lift, so no takeoff

im an aerospace engineering student, and he wont take mine or anyone of my aerospace's buddies answer; please help me settle this! i got $400 on it

[/ QUOTE ]
If it helps, I'm not sure NLSoldier is right, but you're wrong.

[/ QUOTE ]

Dear god I hope you are not a practicing rocket scientist

tolbiny

11-23-2005, 03:15 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
The problem with this scenario is that the drive isn't created by the wheels, so this belt wouldn't result in the plane not moving, it would mean the wheels would be moving REALLY quickly, but the thrust would still push teh plane forward.

This scenario is impossible.

[/ QUOTE ]

Yeah, the exact speed I think will be determined by the friction in the axels given that the wheels are not skidding in any way.

[/ QUOTE ]

I was thinking about this earlier, too. I think the wheel speed/conveyor speed would basically accelerate exponentially until the plane took off. Clearly this whole scenario is probably not physically possible, but it's an interesting theory to discuss.

[/ QUOTE ]

Wait- How much money do we have in the crimson challenge fund? Lets give it a go!!!

11-23-2005, 03:15 PM

Subject line = my accredidation

To answer Daryn's question:
Let the system be the fan/board/block. There are no net external forces acting on the system. Thus, the system doesn't move. If you don't like that answer, then look at it a little more microscopically: The fan exerts a force on the air towards the left. By Newton's third law, the air exerts the same force on the fan to the right. The fan force pushes the block to the left with the same force. So the block pushes the skateboard to the left with some force, and the fan pushes the skateboard to the right with the same force (by friction) and the skateboard doesn't move. If htere's no friction, the skateboard will still not move, but the block will move to the left with some acceleration, and the fan will move to the right with some acceleration. The relative amount of acceleration depends on the relative masses of the block and fan- whichever has more mass, accelerates less.

For the plane example, if the belt is moving at some velocity v, then it appears to an observer stationed on the wheel of the plane that the plane is moving at a velocity equal to 2v *relative to the belt*. However, lift is generated by velocity of the air over the wing. The air is not attached to the belt, so the the observer on the wheel sees a velocity of 0 *relative to the air* and thus there is no lift. For those people confused about the two different relative velocities, think about driving a car- you don't think that the passenger is moving relative to you, but you're moving relative to the road.

Patrick del Poker Grande

11-23-2005, 03:16 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
You realize that in your OP, wheel speed = anything, plane speed = 0.

Obv, if the plane isn't moving forward relative to the air, it doesn't take off.

Unless, of course, your plan was to phrase a question with a clear answer, then try to confuse people so you would have a big thread.

[/ QUOTE ]

I've said this multiple times now - at no point in this thread did I say plane speed = zero.

I suggest following Patrick's advice and creating a FBD.

[/ QUOTE ]

UHHHHHHHHHHH what is your point.

Either the conveyor belt is moving exactly opposite of the plane or it is not.

HOW is the plane moving? I would love to know, so I can throw my engineering degree in the trash.

[/ QUOTE ]
This is a plane, not a car.

NLSoldier

11-23-2005, 03:17 PM

mmbt0ne

11-23-2005, 03:17 PM

Ok, I think this will help some people. The numbers aren't really forces, and it's really confusing, but I didn't feel like painting out the explanation on a laptop. Basically, the plane is still moving along the conveyer belt. Think of the engines like a rope pulling the plane.

http://www.f2f2s.com/images/plane.jpg

Eurotrash

11-23-2005, 03:18 PM

edit: nevermind

daryn

11-23-2005, 03:19 PM

[ QUOTE ]
Let the system be the fan/board/block. There are no net external forces acting on the system. Thus, the system doesn't move.

[/ QUOTE ]

my, that was easy. go umass!

11-23-2005, 03:19 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
You realize that in your OP, wheel speed = anything, plane speed = 0.

Obv, if the plane isn't moving forward relative to the air, it doesn't take off.

Unless, of course, your plan was to phrase a question with a clear answer, then try to confuse people so you would have a big thread.

[/ QUOTE ]

I've said this multiple times now - at no point in this thread did I say plane speed = zero.

I suggest following Patrick's advice and creating a FBD.

[/ QUOTE ]

UHHHHHHHHHHH what is your point.

Either the conveyor belt is moving exactly opposite of the plane or it is not.

HOW is the plane moving? I would love to know, so I can throw my engineering degree in the trash.

[/ QUOTE ]
This is a plane, not a car.

[/ QUOTE ]

NO. It IS a car, because it WONT take off.

11-23-2005, 03:19 PM

This is 100% wrong. Think about going to an airport and getting on the conveyer belt. Which direction should the conveyer belt run relative to the direction you're running so that you go faster?

Hiding

11-23-2005, 03:20 PM

Is it possible that the friction from the conveyor belt on the surrounding air creates enough air velocity to give the wings lift?

mmbt0ne

11-23-2005, 03:21 PM

[ QUOTE ]
This is 100% wrong. Think about going to an airport and getting on the conveyer belt. Which direction should the conveyer belt run relative to the direction you're running so that you go faster?

[/ QUOTE ]

WTF? We are entirely aware that the belt is moving in the opposite direction you want to go. You understand that too right?

11-23-2005, 03:23 PM

NLsoldier owes you $400.

daryn

11-23-2005, 03:24 PM

[ QUOTE ]
ok, so I thought I knew how a plane worked, but this thread has me second guessing myself.

I always thought the turbine engines on the plane drew air through them (and past the wings) and out the back, propelling the craft forward. is this correct?

[/ QUOTE ]

the propeller/engine/whatever just acts as if it was a hand pushing the plane forward. the air that moves over the wings (providing lift) is just regular air, usually just chilling.

you can look at it both ways.. either the plane is moving through still air or the air is flowing over the still wing. either way the same thing happens

Shajen

11-23-2005, 03:26 PM

[ QUOTE ]
I have an urge to do more MS Paint.

[/ QUOTE ]

Fire away, Cap'n.

goofball

11-23-2005, 03:26 PM

why didn't I find this thread sooner. The whole sum of the forces = 0 so acceleration = 0 is of course right re: the skateboard.

The airplane question is about the simplest question ever. How could a reasonable person think that the wheels spinning is what makes the plane fly? Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

Redd

11-23-2005, 03:27 PM

[ QUOTE ]
Alright, kids. I'm going to let you in on a little rocket science secret. Prop planes do not generate lift by blowing air over the wings.

[/ QUOTE ]
They don't? Do you mean that they don't make lift by blowing the air themselves, or that the airflow across the wings from whatever source doesn't generate any lift?

As for the OP's question, it looks to me like the plane will take off. If there's zero friction in the wheel bearings, they can't exact any forces tangential to gravity on the plane.

So we have a forward force provided by the thrust and that's it, resulting in forward acceleration. The runway can move at whatever speed it wants, and the wheels will spin faster but they can't apply that force to the plane. In this particular example, the wheels will just spin with twice the angular velocity than they would with a fixed runway.

It's very much like a float plane taking off from the water (where there's also negligible friction).

Slow Play Ray

11-23-2005, 03:28 PM

[ QUOTE ]
[ QUOTE ]
Let the system be the fan/board/block. There are no net external forces acting on the system. Thus, the system doesn't move.

[/ QUOTE ]

my, that was easy. go umass!

[/ QUOTE ]

Hey, why is my answer no good? I am UMass as well, damnit!

*Edit* The reason I said it would go backwards as pictured is because that block is not big enough to "catch" all of the wind from the fan. Hence the "perfect sail" statement.

codewarrior

11-23-2005, 03:29 PM

I retract my original answer. /images/graemlins/tongue.gif

It is so obvious it is complicated, if that makes sense.

I suck at life.

11-23-2005, 03:30 PM

[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

mmbt0ne

11-23-2005, 03:32 PM

[ QUOTE ]
[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

[/ QUOTE ]

Please let me know what company you end up working for so that I can stay off their planes.

11-23-2005, 03:33 PM

[ QUOTE ]
[ QUOTE ]

It's very much like a float plane taking off from the water (where there's also negligible friction).

[/ QUOTE ]

No it is not. It would be like a float plane taking off from a river that is moving at an opposite speed of the floats. WOULD NOT TAKE OFF

To simplify:

1. Plane on a runway. Takes off
2. Plane with locked wheels on ice. Takes off.
3. Plane with locked wheels on runway. Doesn't take off.

Note that #3 is the same problem that OP phrased.

Slow Play Ray

11-23-2005, 03:33 PM

[ QUOTE ]
[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

[/ QUOTE ]

Please explain specifically what FORCE is stopping the plane from moving forward (relative to the atmosphere, NOT the conveyor belt).

11-23-2005, 03:33 PM

[ QUOTE ]
[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

[/ QUOTE ]

I can't believe you're going to be an aerospace engineer /images/graemlins/crazy.gif

daryn

11-23-2005, 03:34 PM

mmbt0ne

11-23-2005, 03:34 PM

11-23-2005, 03:35 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

[/ QUOTE ]

Please explain specifically what FORCE is stopping the plane from moving forward (relative to the atmosphere, NOT the conveyor belt).

[/ QUOTE ]

isn't the whole premise of this post is that the plane isn't moving?

Eurotrash

11-23-2005, 03:36 PM

[ QUOTE ]
[ QUOTE ]
I have an urge to do more MS Paint.

[/ QUOTE ]

Fire away, Cap'n.

[/ QUOTE ]

no inspiration. I need a new topic.

Slow Play Ray

11-23-2005, 03:36 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

[/ QUOTE ]

Please explain specifically what FORCE is stopping the plane from moving forward (relative to the atmosphere, NOT the conveyor belt).

[/ QUOTE ]

isn't the whole premise of this post is that the plane isn't moving?

[/ QUOTE ]

oh my freaking god - how many times do i have to say this? NOWHERE in this thread did i say that the plane wasn't moving. you are ASSUMING that the plane isn't moving, and that's why you can't understand the problem.

11-23-2005, 03:36 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

[/ QUOTE ]

Please explain specifically what FORCE is stopping the plane from moving forward (relative to the atmosphere, NOT the conveyor belt).

[/ QUOTE ]

isn't the whole premise of this post is that the plane isn't moving?

[/ QUOTE ]

I suggest you start at page one and read the thread over again.

daryn

11-23-2005, 03:37 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]

It's very much like a float plane taking off from the water (where there's also negligible friction).

[/ QUOTE ]

No it is not. It would be like a float plane taking off from a river that is moving at an opposite speed of the floats. WOULD NOT TAKE OFF

To simplify:

1. Plane on a runway. Takes off
2. Plane with locked wheels on ice. Takes off.
3. Plane with locked wheels on runway. Doesn't take off.

Note that #3 is the same problem that OP phrased.

[/ QUOTE ]

#3 is nothing like what OP phrased. Explain how the wheels will move at the same speed as the plane in this example.

[/ QUOTE ]

i'm curious to know why the wheels have to be locked for the plane to take off on ice

mmbt0ne

11-23-2005, 03:37 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]

It's very much like a float plane taking off from the water (where there's also negligible friction).

[/ QUOTE ]

No it is not. It would be like a float plane taking off from a river that is moving at an opposite speed of the floats. WOULD NOT TAKE OFF

To simplify:

1. Plane on a runway. Takes off
2. Plane with locked wheels on ice. Takes off.
3. Plane with locked wheels on runway. Doesn't take off.

Note that #3 is the same problem that OP phrased.

[/ QUOTE ]

#3 is nothing like what OP phrased. Explain how the wheels will move at the same speed as the plane in this example.

[/ QUOTE ]

i'm curious to know why the wheels have to be locked for the plane to take off on ice

[/ QUOTE ]

Because otherwise the wheels would slip on the ice and keep you in the same place daryn!!

Hiding

11-23-2005, 03:37 PM

[ QUOTE ]
Please explain specifically what FORCE is stopping the plane from moving forward (relative to the atmosphere, NOT the conveyor belt).

[/ QUOTE ]

That actually cleared it up for me.

CrazyEyez

11-23-2005, 03:38 PM

[ QUOTE ]
[ QUOTE ]
Alright, kids. I'm going to let you in on a little rocket science secret. Prop planes do not generate lift by blowing air over the wings.

[/ QUOTE ]
They don't? Do you mean that they don't make lift by blowing the air themselves, or that the airflow across the wings from whatever source doesn't generate any lift?

As for the OP's question, it looks to me like the plane will take off. If there's zero friction in the wheel bearings, they can't exact any forces tangential to gravity on the plane.

So we have a forward force provided by the thrust and that's it, resulting in forward acceleration. The runway can move at whatever speed it wants, and the wheels will spin faster but they can't apply that force to the plane. In this particular example, the wheels will just spin with twice the angular velocity than they would with a fixed runway.

It's very much like a float plane taking off from the water (where there's also negligible friction).

[/ QUOTE ]
I get that. I mean I get how the plane can take off, I just don't get how you can say that the wheels are moving at the same speed as the conveyor. I guess I don't understand what speed means. /images/graemlins/confused.gif

jba

11-23-2005, 03:38 PM

this thread is seriously the bomb.

let's think a little about OP's original statement, that the conveyor belt is moving in the opposite direction as the wheels on the plane.

now imagine the plane is completely turned off, there is 0 thrust from the turbines/props. The conveyor belt is moving backwards at 100 feet/sec. The planes wheels are spinning forwards at the same rate. The plane is standing still, no??

now what happens when you turn on the turbines and start generating forward thrust, WTF do you think the plane is going to do???

Slow Play Ray

11-23-2005, 03:38 PM

[ QUOTE ]
Because otherwise the wheels would slip on the ice and keep you in the same place daryn!!

[/ QUOTE ]

LOL!

jman220

11-23-2005, 03:38 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
yeah it def. blew my mind. now give the answer plz? and the answer to daryns skateboard thing too. me and my friend have a bet on both.

[/ QUOTE ]

The plane can take off - this has already been established.

For Darryn's - as pictured, the skateboard would go backwards. If it were a perfect sail instead of that board, it would stand still.

[/ QUOTE ]

describe a perfect sail

[/ QUOTE ]

Apologies if this answer has ben posted ( i haven't gotten that far), but the fan/sail would have to be a closed system.

poincaraux

11-23-2005, 03:39 PM

wow! you win!

11-23-2005, 03:40 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

[/ QUOTE ]

Please explain specifically what FORCE is stopping the plane from moving forward (relative to the atmosphere, NOT the conveyor belt).

[/ QUOTE ]

Uh. The conveyor belt moves at the same speed as the
wheels as stated in the problem. Thus the plane cannot move forward.

Seriously how much physics do you understand? Are you familiar with reference frames?

Ulysses

11-23-2005, 03:41 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

[/ QUOTE ]

Please explain specifically what FORCE is stopping the plane from moving forward (relative to the atmosphere, NOT the conveyor belt).

[/ QUOTE ]

isn't the whole premise of this post is that the plane isn't moving?

[/ QUOTE ]

I just skimmed this thread.

The issue isn't whether or not the plane is moving on the runway.

It's about whether or not air is moving across the plane's wings.

Slow Play Ray

11-23-2005, 03:41 PM

[ QUOTE ]
Uh. The conveyor belt moves at the same speed as the
wheels as stated in the problem. Thus the plane cannot move forward.

[/ QUOTE ]

Seriously how much physics do you understand? Are you familiar with reference frames?

IndieMatty

11-23-2005, 03:41 PM

[ QUOTE ]
Ok, I think this will help some people. The numbers aren't really forces, and it's really confusing, but I didn't feel like painting out the explanation on a laptop. Basically, the plane is still moving along the conveyer belt. Think of the engines like a rope pulling the plane.

http://www.f2f2s.com/images/plane.jpg

[/ QUOTE ]

Me like funny picture. Ryan make no funny. Me sad.

mmbt0ne

11-23-2005, 03:42 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

[/ QUOTE ]

Please explain specifically what FORCE is stopping the plane from moving forward (relative to the atmosphere, NOT the conveyor belt).

[/ QUOTE ]

Uh. The conveyor belt moves at the same speed as the
wheels as stated in the problem. Thus the plane cannot move forward.

Seriously how much physics do you understand? Are you familiar with reference frames?

[/ QUOTE ]

Explain how the wheels will move at the same speed as the plane in this example.

11-23-2005, 03:43 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

[/ QUOTE ]

Please explain specifically what FORCE is stopping the plane from moving forward (relative to the atmosphere, NOT the conveyor belt).

[/ QUOTE ]

Uh. The conveyor belt moves at the same speed as the
wheels as stated in the problem. Thus the plane cannot move forward.

Seriously how much physics do you understand? Are you familiar with reference frames?

[/ QUOTE ]

Explain how the wheels will move at the same speed as the plane in this example.

[/ QUOTE ]

THIS JUST IN:

WHEELS ARE ATTACHED TO THE PLANE

11-23-2005, 03:43 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

[/ QUOTE ]

Please explain specifically what FORCE is stopping the plane from moving forward (relative to the atmosphere, NOT the conveyor belt).

[/ QUOTE ]

isn't the whole premise of this post is that the plane isn't moving?

[/ QUOTE ]

I just skimmed this thread.

The issue isn't whether or not the plane is moving on the runway.

It's about whether or not air is moving across the plane's wings.

[/ QUOTE ]

thats exactly what im basing my arguement on; if the plane isn't moving relative to the atmosphere, the plane doesn't take off....game over

11-23-2005, 03:43 PM

[ QUOTE ]
The runway moves in the opposite direction of the plane at the exact same speed as the plane's wheels.

[/ QUOTE ]

The plane itself and the plane's wheels are not moving at the same speed. Everyone who doesn't understand that the plane will take off seems to be missing this.

Eurotrash

11-23-2005, 03:45 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

[/ QUOTE ]

Please explain specifically what FORCE is stopping the plane from moving forward (relative to the atmosphere, NOT the conveyor belt).

[/ QUOTE ]

Uh. The conveyor belt moves at the same speed as the
wheels as stated in the problem. Thus the plane cannot move forward.

Seriously how much physics do you understand? Are you familiar with reference frames?

[/ QUOTE ]

Explain how the wheels will move at the same speed as the plane in this example.

[/ QUOTE ]

THIS JUST IN:

WHEELS ARE ATTACHED TO THE PLANE

[/ QUOTE ]

dude, one sec. if the plane's velocity is 100 mph in the +x direction and the conveyor's velocity is 100 mph in the -x direction (and the turbines are off), we agree that the plane is not moving relative to the ground, correct?

now what happens if you apply a force to the plane in the +x direction? is it locked in space? can it not move?

jba

11-23-2005, 03:46 PM

[ QUOTE ]

THIS JUST IN:

WHEELS ARE ATTACHED TO THE PLANE

[/ QUOTE ]

this just in:

wheels can spin

CrazyEyez

11-23-2005, 03:47 PM

[ QUOTE ]
this thread is seriously the bomb.

let's think a little about OP's original statement, that the conveyor belt is moving in the opposite direction as the wheels on the plane.

now imagine the plane is completely turned off, there is 0 thrust from the turbines/props. The conveyor belt is moving backwards at 100 feet/sec. The planes wheels are spinning forwards at the same rate. The plane is standing still, no??

now what happens when you turn on the turbines and start generating forward thrust, WTF do you think the plane is going to do???

[/ QUOTE ]
The plane is going to move forward and take off. But once that happens, the wheels are now moving faster than the conveyor, no? That's the only part I question.

mmbt0ne

11-23-2005, 03:47 PM

[ QUOTE ]
[ QUOTE ]
Explain how the wheels will move at the same speed as the plane in this example.

[/ QUOTE ]

THIS JUST IN:

WHEELS ARE ATTACHED TO THE PLANE

[/ QUOTE ]

LOL, you're really not thinking hard enough.

Sabrazack

11-23-2005, 03:47 PM

The wheels are infact moving at the exact same speed as the plane. Otherwise i think the plane might have a hard time rolling on the runway.

11-23-2005, 03:49 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

[/ QUOTE ]

Please explain specifically what FORCE is stopping the plane from moving forward (relative to the atmosphere, NOT the conveyor belt).

[/ QUOTE ]

Uh. The conveyor belt moves at the same speed as the
wheels as stated in the problem. Thus the plane cannot move forward.

Seriously how much physics do you understand? Are you familiar with reference frames?

[/ QUOTE ]

Explain how the wheels will move at the same speed as the plane in this example.

[/ QUOTE ]

THIS JUST IN:

WHEELS ARE ATTACHED TO THE PLANE

[/ QUOTE ]

dude, one sec. if the plane's velocity is 100 mph in the +x direction and the conveyor's velocity is 100 mph in the -x direction (and the turbines are off), we agree that the plane is not moving relative to the ground, correct?

now what happens if you apply a force to the plane in the +x direction? is it locked in space? can it not move?

[/ QUOTE ]

Yeah I totally agree with you here.

The thing is, as stated in the original problem, the runway speeds up to compensate for the extra +x force.

jba

11-23-2005, 03:50 PM

[ QUOTE ]
[ QUOTE ]
dude, one sec. if the plane's velocity is 100 mph in the +x direction and the conveyor's velocity is 100 mph in the -x direction (and the turbines are off), we agree that the plane is not moving relative to the ground, correct?

now what happens if you apply a force to the plane in the +x direction? is it locked in space? can it not move?

[/ QUOTE ]

Yeah I totally agree with you here.

The thing is, as stated in the original problem, the runway speeds up to compensate for the extra +x force.

[/ QUOTE ]

and the wind does too???

LAGmaniac

11-23-2005, 03:50 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

[/ QUOTE ]

Please explain specifically what FORCE is stopping the plane from moving forward (relative to the atmosphere, NOT the conveyor belt).

[/ QUOTE ]

Uh. The conveyor belt moves at the same speed as the
wheels as stated in the problem. Thus the plane cannot move forward.

Seriously how much physics do you understand? Are you familiar with reference frames?

[/ QUOTE ]

Explain how the wheels will move at the same speed as the plane in this example.

[/ QUOTE ]

THIS JUST IN:

WHEELS ARE ATTACHED TO THE PLANE

[/ QUOTE ]

You do realize that a plane's wheels spin freely like a car in neutral not a car in gear, right?

jba

11-23-2005, 03:51 PM

11-23-2005, 03:52 PM

[ QUOTE ]
The thing is, as stated in the original problem, the runway speeds up to

[/ QUOTE ]

Wait, you understand this point and still think it can't take off? Holy hell.

Edited for clarity

11-23-2005, 03:52 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
dude, one sec. if the plane's velocity is 100 mph in the +x direction and the conveyor's velocity is 100 mph in the -x direction (and the turbines are off), we agree that the plane is not moving relative to the ground, correct?

now what happens if you apply a force to the plane in the +x direction? is it locked in space? can it not move?

[/ QUOTE ]

Yeah I totally agree with you here.

The thing is, as stated in the original problem, the runway speeds up to compensate for the extra +x force.

[/ QUOTE ]

and the wind does too???

[/ QUOTE ]

the [censored] does that matter

Patrick del Poker Grande

11-23-2005, 03:52 PM

mmbt0ne

11-23-2005, 03:52 PM

[ QUOTE ]
Yeah I totally agree with you here.

The thing is, as stated in the original problem, the runway speeds up to compensate for the extra +x force.

[/ QUOTE ]

Why does the tangential velocity of the wheels increase with the thrust of the engines in this system?

housenuts

11-23-2005, 03:53 PM

[ QUOTE ]

http://www.dartmouth.edu/~physics/lecture_demo/images/mechanics/skateboard.l.jpg

when the fan is plugged in, what happens? will the skateboard move? provide reasoning!

[/ QUOTE ]

the skateboard will move in a rearwards circle (the radius of this circle being pi * length of skateboard) once it has completed 5 rotations it will continue on it's path only this time the force of the wind will push the rear end up and it will go around doing a nose manual

codewarrior

11-23-2005, 03:54 PM

[ QUOTE ]
The wheels center of gravity [is] infact moving at the exact same speed as the plane.

[/ QUOTE ]

The wheels don't exert any force on the plane.

11-23-2005, 03:54 PM

[ QUOTE ]
[ QUOTE ]
Yeah I totally agree with you here.

The thing is, as stated in the original problem, the runway speeds up to compensate for the extra +x force.

[/ QUOTE ]

Why does the tangential velocity of the wheels increase with the thrust of the engines in this system?

[/ QUOTE ]

Is this a serious question? Of course it increases. You are adding force in the tangential direction---> wheels spin faster.

Patrick del Poker Grande

11-23-2005, 03:55 PM

mmbt0ne

11-23-2005, 03:56 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Yeah I totally agree with you here.

The thing is, as stated in the original problem, the runway speeds up to compensate for the extra +x force.

[/ QUOTE ]

Why does the tangential velocity of the wheels increase with the thrust of the engines in this system?

[/ QUOTE ]

Is this a serious question? Of course it increases. You are adding force in the tangential direction---> wheels spin faster.

[/ QUOTE ]

How are we adding force in the tangential direction?

BTW, I'm not being a smartass, we're actually getting close.

jba

11-23-2005, 03:56 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
dude, one sec. if the plane's velocity is 100 mph in the +x direction and the conveyor's velocity is 100 mph in the -x direction (and the turbines are off), we agree that the plane is not moving relative to the ground, correct?

now what happens if you apply a force to the plane in the +x direction? is it locked in space? can it not move?

[/ QUOTE ]

Yeah I totally agree with you here.

The thing is, as stated in the original problem, the runway speeds up to compensate for the extra +x force.

[/ QUOTE ]

and the wind does too???

[/ QUOTE ]

the [censored] does that matter

[/ QUOTE ]

well I didn't mean wind I really meant air, I just meant so what if the runway speeds up, it isn't the planes velocity wrt to the runway that matters it is the velocity wrt the air, which does not speed up as the

on second thought I'm starting to get the feeling you are just not going to get this

goofball

11-23-2005, 03:59 PM

[ QUOTE ]
[ QUOTE ]
this thread is seriously the bomb.

let's think a little about OP's original statement, that the conveyor belt is moving in the opposite direction as the wheels on the plane.

now imagine the plane is completely turned off, there is 0 thrust from the turbines/props. The conveyor belt is moving backwards at 100 feet/sec. The planes wheels are spinning forwards at the same rate. The plane is standing still, no??

now what happens when you turn on the turbines and start generating forward thrust, WTF do you think the plane is going to do???

[/ QUOTE ]
The plane is going to move forward and take off. But once that happens, the wheels are now moving faster than the conveyor, no? That's the only part I question.

[/ QUOTE ]

Right. The OP's question specifically states that "The runway moves in the opposite direction of the plane at the exact same speed as the plane's wheels."

For this to be true it seems like the plane must be stationary with respect to the whole runway (or ground if that's easier. It won't be stationary relative to an individual point on the runway, just with whole conveyorbelt loop or whatever). Imagine the runway is moving backward at 10 m/s. In 1 second if the plane is stationary the wheels will ahve 'rolled' 10m same as the runway. I put rolled in quotes because it's ambiguous. The runway is moving, the wheels are spinning. The linear amount of wheel that has touched the ground is 10m, which likely represents many rotations of the wheel. Anyway, the wheel rolls 10m in that same second. Imagine the plane moves forward 1m in that second. Now the wheel has covered more runway conveyor in the same amount of time and is moving faster than the runway conveyor. According to the original question we can't have this happen.

Perhaps a better way to phrase the OP would have been "airplnae has top airspeed of x, wheels are frictionless, conveyor runway moves backward with speed 2x, can the airplane take off"

Patrick del Poker Grande

11-23-2005, 04:00 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

[/ QUOTE ]

Please explain specifically what FORCE is stopping the plane from moving forward (relative to the atmosphere, NOT the conveyor belt).

[/ QUOTE ]

isn't the whole premise of this post is that the plane isn't moving?

[/ QUOTE ]

I just skimmed this thread.

The issue isn't whether or not the plane is moving on the runway.

It's about whether or not air is moving across the plane's wings.

[/ QUOTE ]

thats exactly what im basing my arguement on; if the plane isn't moving relative to the atmosphere, the plane doesn't take off....game over

[/ QUOTE ]
While it is completely true that there is no lift if the plane isn't moving relative to the atmosphere, you've made quite an incrorrect assumption that the plane is not moving relative to the atmosphere.

Bluffoon

11-23-2005, 04:00 PM

Yes. Obviously.

LAGmaniac

11-23-2005, 04:02 PM

[ QUOTE ]

The thing is, as stated in the original problem, the runway speeds up to compensate for the extra +x force.

[/ QUOTE ]

But that's the issue here, CAN the runway compensate for the thrust of the engines? Imagine the wheels are frictionless, and the conveyor belt is spinning backwards at 100 mph and the plane is just sitting there, engines at idle. The conveyor belt has no effect on the plane and therefore has no way to counteract the thrust of the plane.

Of course in the real world there is friction in the wheels and the conveyor belt will exert a small rearward force, but it will never be enough to counteract the thrust of the plane.

Soul Daddy

11-23-2005, 04:02 PM

Is this close to getting wrapped up with a nice little bow? Apparently there are no more diagrams coming and my head hurts.

11-23-2005, 04:02 PM

[ QUOTE ]
[ QUOTE ]
The thing is, as stated in the original problem, the runway speeds up to

[/ QUOTE ]

Wait, you understand this point and still think it can't take off? Holy hell.

Edited for clarity

[/ QUOTE ]

OK I will spell it out.

Wheels moving in X with tangential velocity V.

Runway moving in X with -V.

Plane is stationary to observor (the atmosphere).

Engines apply force in +X which translates to increased wheel speed.

Plane is now moving in X with velocity (V + Vfromengine)

Runway speeds up to move in X with velocity
-(V + Vfromengine)

Plane is still stationary to observor(the atmosphere).

Plane does not take off.

MrWookie47

11-23-2005, 04:05 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
The thing is, as stated in the original problem, the runway speeds up to

[/ QUOTE ]

Wait, you understand this point and still think it can't take off? Holy hell.

Edited for clarity

[/ QUOTE ]

OK I will spell it out.

Wheels moving in X with tangential velocity V.

Runway moving in X with -V.

Plane is stationary to observor (the atmosphere).

Engines apply force in +X which translates to increased wheel speed.

Plane is moving in X with velocity (V + Vfromengine)

Runway speeds up to move in X with velocity
-(V + Vfromengine)

Plane is still stationary to observor(the atmosphere).

Plane does not take off.

[/ QUOTE ]

The bold part is incorrect.

11-23-2005, 04:06 PM

[ QUOTE ]

OK I will spell it out.

[/ QUOTE ]

Please check your spelling and get back to us. I am starting to think you are trolling.

11-23-2005, 04:07 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[/ QUOTE ]

this is it, you need wind over the wings for lift!! a plane cannot get in the air without lift! wtf, i can't believe noone gets this

[/ QUOTE ]

Please explain specifically what FORCE is stopping the plane from moving forward (relative to the atmosphere, NOT the conveyor belt).

[/ QUOTE ]

isn't the whole premise of this post is that the plane isn't moving?

[/ QUOTE ]

I just skimmed this thread.

The issue isn't whether or not the plane is moving on the runway.

It's about whether or not air is moving across the plane's wings.

[/ QUOTE ]

thats exactly what im basing my arguement on; if the plane isn't moving relative to the atmosphere, the plane doesn't take off....game over

[/ QUOTE ]
While it is completely true that there is no lift if the plane isn't moving relative to the atmosphere, you've made quite an incrorrect assumption that the plane is not moving relative to the atmosphere.

[/ QUOTE ]

thats the whole point of the conveyer belt....it stops the plane from going anywhere....you obviously don't move relative to the atmosphere when youre running on a treadmill, right? thats the whole point of a treadmill, so you can run WITHOUT MOVING.

Patrick del Poker Grande

11-23-2005, 04:07 PM

[ QUOTE ]
Is this close to getting wrapped up with a nice little bow? Apparently there are no more diagrams coming and my head hurts.

[/ QUOTE ]
I have to wait for Ray's permission to unleash the full fury on you guys. In the mean time, I've got actual rocket science work to do, so I'm going to have to let this thread go for a while. I can't keep up with it.

Let there be no doubt, though, the plane can take off. For all you retards out there who can't grasp this, think of the babystroller on the moving walkway example provided a while ago (was it 4_2_it or crazyeyes? I don't remember, sorry). It is a very good analogy and shows exactly what's going on here, sans lifting wings.

11-23-2005, 04:08 PM

[ QUOTE ]
[ QUOTE ]
Is this close to getting wrapped up with a nice little bow? Apparently there are no more diagrams coming and my head hurts.

[/ QUOTE ]
I have to wait for Ray's permission to unleash the full fury on you guys. In the mean time, I've got actual rocket science work to do, so I'm going to have to let this thread go for a while. I can't keep up with it.

Let there be no doubt, though, the plane can take off. For all you retards out there who can't grasp this, think of the babystroller on the moving walkway example provided a while ago (was it 4_2_it or crazyeyes? I don't remember, sorry). It is a very good analogy and shows exactly what's going on here, sans lifting wings.

[/ QUOTE ]

PLEASE dont do any rocket science work until you realize why the plane wont take off.

11-23-2005, 04:09 PM

[ QUOTE ]
[ QUOTE ]
Is this close to getting wrapped up with a nice little bow? Apparently there are no more diagrams coming and my head hurts.

[/ QUOTE ]
I have to wait for Ray's permission to unleash the full fury on you guys. In the mean time, I've got actual rocket science work to do, so I'm going to have to let this thread go for a while. I can't keep up with it.

Let there be no doubt, though, the plane can take off. For all you retards out there who can't grasp this, think of the babystroller on the moving walkway example provided a while ago (was it 4_2_it or crazyeyes? I don't remember, sorry). It is a very good analogy and shows exactly what's going on here, sans lifting wings.

[/ QUOTE ]

In this case, as stated in original problem, the speed of the moving walkway is VARIABLE.