Airplane on Conveyor Belt Mythbusters 12/12

[ponyfool]

Southern, Rondo, Xviper. You are wrong. Period. It's been proven time and time again in physics classes throughout the US and probably the world.

Here's more proof for you. But it doesn't matter, because you won't admit you are wrong.

Additional fodder for proof

But, just to throw one more point home, where does the restricting force come from? Why is it you think there's resistance to the forward thrust of the airplane that is completely independent of the treadmill? Or, do you actually think the thrust of a jet engine can't overcome the resistance offered by the wheels contact with the treadmill and the friction in the wheel bearings?

 

[JimLor]

Because the motive force propelling you (guy on the skateboard) forward is not affected by the treadmill. The rope is attached to a something that is not moving with the treadmill. The treadmill could be going 200mph opposite your intended direction and as long as the wheels stay on, you can pull yourself forward. Really.

 

[exskibum]

We all agree that the plane has to move forward to generate airspeed (assuming not a helicopter and no wind), which will generate lift, right?

We all agree that the airplane's prop or jet engine will move the airplane without needing an engine to turn the wheels, and that the thrust of the prop or jet can overcome any backwards directional force of the treadmill, right?

So . . .

Will someone please explain how the airplane can move forward on a treadmill while on the ground and still have the wheels and treadmill turn at the SAME SPEED????**

THAT is what the problem constrains us to. Definitionally, the airplane must be sitting still to satisfy the problem's "same speed" requirement. No?

** (See post nos. 1, 2, 191 and 197)

 

[CDN_FJR]

Logic tells me the plane will take off without a problem. The plane pushes itself forward off of the density of the air, not off of it's traction/friction between the wheel and the ground.

Ding, Ding... we have a winner... the prop is grabbing air as it cork screws through the "fluid" (yes air is considered a fluid). If I was riding a skate board on a treadmill and had something like a rope (or propeller with engine instead of rope strapped to my back) to pull myself forward, I would be able to pull myself off the front of the treadmill. Forward motion would be achieved completely independent of what the skate board or treadmill was doing.

Original problem: " . . . the hypothetical situation of the ability of an airplane to take off if it was on a conveyor belt spinning in the opposite direction of the wheels at the same speed of the wheels."

Please explain how one stays within the parameters of the problem (see highlighted portion above) with forward motion of the plane. If the plane is moving forward (to achieve lift via air moving over and under the wings), then the wheels MUST BE moving at GREATER SPEED than the treadmill. NO???

I'm not arguing that you couldn't throttle up the plane to overcome the rearward force of the treadmill. Of course you could, BUT the wheels would NECESSARILY be moving faster than the treadmill then, AND THAT ISN'T THE WAY THE PROBLEM WAS DEFINED!

Now I know why this is a pointless thread...

 

[madmike2]

Because the motive force propelling you (guy on the skateboard) forward is not affected by the treadmill. The rope is attached to a something that is not moving with the treadmill. The treadmill could be going 200mph opposite your intended direction and as long as the wheels stay on, you can pull yourself forward. Really.

SO, to put this back into the framework of the airplane discusion:

Since the airplane wheels are independent of the power source, even if the treadmill goes in reverse @ 140 mph, the airplane will still move forward at whatever speed the prop determines?

The aircraft would still move forward @ 140 mph but the wheels would then be traveling @ 280 mph "ground" speed? Because the wheels are independent of the power source for the actual movement of the airplane?

I think I'm beginning to see the failure of my original thought process.

_______________________________________________________________________

[SIZE=12pt]As an aside:[/SIZE]

This has been an interesting discussion. Surely something to keep our brains exercised during the Winter "lay-off". But, Gentlemen:

There is no freakin' reason for childish name calling!

We can get along and not take things "personal". Jeez, aren't there enough games played by the cagers with whom we share the road, workplace or other organizations? This should be a place to come in, put your feet up, open your favorite beverage (mine is "iced tea") and enjoy stimulating conversation and the exchange of information.

Perhaps some of you need to do a Google search for "skin thickening agents" of "open minded tonic"?

 

[exskibum]

Logic tells me the plane will take off without a problem. The plane pushes itself forward off of the density of the air, not off of it's traction/friction between the wheel and the ground.

Ding, Ding... we have a winner... the prop is grabbing air as it cork screws through the "fluid" (yes air is considered a fluid). If I was riding a skate board on a treadmill and had something like a rope (or propeller with engine instead of rope strapped to my back) to pull myself forward, I would be able to pull myself off the front of the treadmill. Forward motion would be achieved completely independent of what the skate board or treadmill was doing.

Original problem: " . . . the hypothetical situation of the ability of an airplane to take off if it was on a conveyor belt spinning in the opposite direction of the wheels at the same speed of the wheels."

Please explain how one stays within the parameters of the problem (see highlighted portion above) with forward motion of the plane. If the plane is moving forward (to achieve lift via air moving over and under the wings), then the wheels MUST BE moving at GREATER SPEED than the treadmill. NO???

I'm not arguing that you couldn't throttle up the plane to overcome the rearward force of the treadmill. Of course you could, BUT the wheels would NECESSARILY be moving faster than the treadmill then, AND THAT ISN'T THE WAY THE PROBLEM WAS DEFINED!

Now I know why this is a pointless thread...

[SIZE=18pt]EXACTLY!!!!![/SIZE] [SIZE=12pt] It's a "trick" hidden in the problem. And we spent how many replies to get here?!?[/SIZE]

Whaddya say we find Randy (who started this) and lynch him now that our blood lust is up?? :evil:

 

[Rondo777]

Logic tells me the plane will take off without a problem. The plane pushes itself forward off of the density of the air, not off of it's traction/friction between the wheel and the ground.

Ding, Ding... we have a winner... the prop is grabbing air as it cork screws through the "fluid" (yes air is considered a fluid). If I was riding a skate board on a treadmill and had something like a rope (or propeller with engine instead of rope strapped to my back) to pull myself forward, I would be able to pull myself off the front of the treadmill. Forward motion would be achieved completely independent of what the skate board or treadmill was doing.

CDN, you cant compare a teather to the prop, the teather (without tugging on it) is already keeping you motionless no matter how fast the treadmill moves because the other end is attached to somthing stationary . so any additional force you apply to the teather is whats making you move forward, your forgetting the force the teather is already using to keep you still to begin with. The teather is attached to somthing in front of you and your just pulling yourself along it. essentially your climbing a rope only horizontally. On the other hand, the prop or jet of the plane would have to at least compensate for the movement of the treadmill to keep the plane from going backwards. Take your teather, turn it vertical and climb on, now stop. Now your not moving, just like the plane. Do you think that the rope is doing nothing? Maybe you can let go and just float there. The rope is exerting enough force to keep you suspended, the teather is doing the same thing for the plane on the treadmill even before you give it the tug. If you untied the rope you were climbing you would fall on your ***, if you cut the teather holding the plane it would move backwards as it is sitting on a moving treadmill and now theres no teather to COMPENSATE for that motion.

 

[JimLor]

It's amazing how clarity comes when you read the f...ing premise! I think I must now apologize for calling myself a dolt and go back to my original answer, however, that answer was arrived at without a complete understanding of the starting point - IOW, right answer but wrong logic! And my second answer, while correct to the situation I layed out, was wrong in regards to the original situation.

You know what, I'm going down to the garage to ride ole' Maxine home and cogitate on this some more. I'll be back in about 50 miles!

And I'm with you Mike!

 

[Rondo777]

Logic tells me the plane will take off without a problem. The plane pushes itself forward off of the density of the air, not off of it's traction/friction between the wheel and the ground.

Ding, Ding... we have a winner... the prop is grabbing air as it cork screws through the "fluid" (yes air is considered a fluid). If I was riding a skate board on a treadmill and had something like a rope (or propeller with engine instead of rope strapped to my back) to pull myself forward, I would be able to pull myself off the front of the treadmill. Forward motion would be achieved completely independent of what the skate board or treadmill was doing.

Original problem: " . . . the hypothetical situation of the ability of an airplane to take off if it was on a conveyor belt spinning in the opposite direction of the wheels at the same speed of the wheels."

Please explain how one stays within the parameters of the problem (see highlighted portion above) with forward motion of the plane. If the plane is moving forward (to achieve lift via air moving over and under the wings), then the wheels MUST BE moving at GREATER SPEED than the treadmill. NO???

I'm not arguing that you couldn't throttle up the plane to overcome the rearward force of the treadmill. Of course you could, BUT the wheels would NECESSARILY be moving faster than the treadmill then, AND THAT ISN'T THE WAY THE PROBLEM WAS DEFINED!

Now I know why this is a pointless thread...

[SIZE=18pt]EXACTLY!!!!![/SIZE] [SIZE=12pt] It's a "trick" hidden in the problem. And we spent how many replies to get here?!?[/SIZE]

Whaddya say we find Randy (who started this) and lynch him now that our blood lust is up?? :evil:

I think when they say the wheels are moving at the same speed as the treadmill they actually mean the the wheel is spinning at a rate that would keep the plane stationary. The actual SPEED that the wheel is spinning would be completly arbitrary depending on the circomfrence of the tire.

 

[RadioHowie]

EDIT:

Delete...delete...delete.

I can't believe I fell for this topic AGAIN!

 

[germany]

 

[SouthernCruizer]

*****************

Yes, I have seen that video...its great....its the one where the plane is travellling at approx. 0 mph while the treadmill is spinning, and then it lifts straight up like a helicopter....cooooool

 

[germany]

This is what was happening inside the airplane when it took off. This guy couldn't handle it.

Clicky

:crazy:

 

[ponyfool]

OK, here's the clincher. This will show you the fault in your logic.

Replace the wheels of an airplane with skids, like on a sled. When the plane is stopped, the treadmill is stopped. The plane applies thrust, but doesn't go anywhere because the friction between the skids and treadmill are still too great. It applies more thrust and finally achieves enough thrust to overcome the stationary friction and starts to move forward. But, the treadmill starts to turn to match the speed of the plane. However, since the skids are sliding along the treadmill, and because sliding friction is LESS than stationary friction, the plane will continue to move regardless of how fast the treadmill is spinning. When the plane reaches normal liftoff speed, it will be flying.

Does that help you understand the fault in your link between the wheels and the treadmill? Or do you somehow think that by having the treadmill spinning faster the plane with the skids will somehow still stand still?

It's ok to acknowledge you are wrong. It's simply foolish to insist you aren't!

 

[Fred W]

Winter has not even officially arrived yet and there seem to be an inordinate number of severe cases of the dreaded PMS (Parked Motorcycle Syndrome) :dribble:

 

[Toecutter]

Or, do you actually think the thrust of a jet engine can't overcome the resistance offered by the wheels contact with the treadmill and the friction in the wheel bearings?

It totally depends on the ABEC rating of those bearings, dude....

Given enough interest and action, every NEPRT thread will eventually be locked down.

Why can't we all just see it my way?

 

[germany]

[SIZE=12pt]As an aside:[/SIZE]
This has been an interesting discussion. Surely something to keep our brains exercised during the Winter "lay-off". But, Gentlemen:

There is no freakin' reason for childish name calling!

If you are going to call each other names, it is best to use the Admin approved names like:

******, 'Tard, Dickless Wonder, ********, and Weasel-**** as used here.

 

[Rondo777]

EDIT:
Delete...delete...delete.

I can't believe I fell for this topic AGAIN!

Me neither. I was just looking over all the times i've participated in this thread. Although I know I did'nt say anything offensive I hope I havn't come off as a know it all. I just got really got rapped up in this topic. I think the episode is airing on like the 20th or 21st. I'm sure the busters will screw it up and there will never be resolution. I'm done, I have babbled my final Babble. Have a Great weekend everyone. The weather is supposed to be in the 60's and sunny here in AZ this weekend and I look forward to riding. Of course if I come across a tread mill I'll just ride right on and report how much throttle I had to crank in to get the Feejer airborn!

 

[rayban]

This is simple. Take some private pilot ground school lessons (better yet, get your license, it's easy, I soloed at 11 hours and got my ticket at the minimum).

Lift requires airflow, period, end of story. Lift is generated by a differential in pressures above and below the wing. That differential can only be generated by flow passing over the airfoil. In fixed wing craft, that requires forward progress (or one HELL of a headwind!) The reason aircraft carriers turn into the wind and why private pilots pick which end of the runway to use based on the windsock (and automated weather reporting over the radio) is to maximize airflow speed by flying into the wind instead of away from it. More headwind = more airflow velocity over the airfoils. Same reason you land into the wind. More flow = more control up to the last minute when you flare up to kill off vertical descent and bleed off a bit more forward velocity as you (hopefully) gracefully kiss the earth with your tires.

In rotary-wing craft, the "wings" are spun in a circle to get the air flowing over them. Faster spin and/or more angle of attack to the foil (to a point) = more lift. The forward ground speed, both absolute and relative to wind flow, is totally pointless except from the aforementioned "headwind/tailwind" factor.

If wheel velocity had anything to do with generating pressure differential and, in turn, lift, then every car that gets smog inspected by spinning those rollers is at risk of eventually spontaneously lifting off into the air....LOL

Either way, "wheel velocity" is pointless. I'd love to meet the idiots who espouse that theory and sell them a few bridges...

To the other point, it is somewhat amusing that some of the participants who scold others for name calling are themselves often guilty of having some of the most caustic, sarcastic, bossy and generally snooty snotball posts in the last 6 months. Glass houses, stones thrown, enough said.

 

[Fred W]

[SIZE=12pt]As an aside:[/SIZE]
This has been an interesting discussion. Surely something to keep our brains exercised during the Winter "lay-off". But, Gentlemen:

There is no freakin' reason for childish name calling!

If you are going to call each other names, it is best to use the Admin approved names like:

******, 'Tard, Dickless Wonder, ********, and Weasel-**** as used here.

Yeah, so FYYFF's! :****: