Jet vs Conveyor question

[Aerovette]

After years of dissmissive replies to this question, simply stating the jet will not take off, I find myself in an actual on line debate on the topic. I am firm in my conviction that the plane cannot take off, but the guy stating it will is equally insistant that it will and bragging about his expertise like Yaddie on his birthday.

The example he posed is this...

Place a model car (passive wheels) on a treadmill. You can easily push it forward (jet thrust) in spite of the opposition of the treadmill.

I argued that once you apply thrust (pushing the model) you have created a differential between the conveyor speed and the wheel speed, which according to the question posed, are always a match in the opposite direction. Therefore, applying a push to the model, also requires and equal increase in opposition from the conveyor. In a static position, there is no airflow or pressure differential over the wings, and therefore no lift.

I also compared putting your hand out the window of a car going 120mph and putting your hand out the window of a car on a dyno reading 120mph. There will be no wind on the hand on the dyno.

Now I come to you good people to dispell this myth that the plane will take off.

As an extra challenge, the other party states it was proven on Mythbusters and I myself consulted ChatGPT which claims the plain will take off.

[higgyburners]

I apply the same logic to ***** farts.... I hope this helps

[Unsuspicious]

The plane will take off because the plane will move forward.

Wheel speed and conveyor speed is irrelevant because they are decoupled from the plane. Only the speeds are matched, not the force.

Think of it this way- can a plane remain in place while the wheels spin? Yes, regardless of wheel spin direction and speed. Since the plane could remain in place regardless of wheel spin or speed, it follows that the plane can move regardless of wheel and conveyor.

Wheel speed is not plane speed. If that were the case, we could land a 747 on a dime if we had a conveyor matching air speed as it touched down. People who think a conveyor belt can stop a plane from moving must concede that it's possible to land a plane on a dime, basically. And from that, we know they're wrong.

[Aerovette]

The plane will take off because the plane will move forward.

Wheel speed and conveyor speed is irrelevant because they are decoupled from the plane. Only the speeds are matched, not the force.

Think of it this way- can a plane remain in place while the wheels spin? Yes, regardless of wheel spin direction and speed. Since the plane could remain in place regardless of wheel spin or speed, it follows that the plane can move regardless of wheel and conveyor.

Wheel speed is not plane speed. If that were the case, we could land a 747 on a dime if we had a conveyor matching air speed as it touched down. People who think a conveyor belt can stop a plane from moving must concede that it's possible to land a plane on a dime, basically. And from that, we know they're wrong.

Thrust from the jet, rolls the plane forward. No thrust would cause the conveyor to move the plane backward. That means there is a point of equilibrium. The thrust translates to wheel speed on a runway. That speed on a conveyor is cancelled.

[Unsuspicious]

Thrust from the jet, rolls the plane forward. No thrust would cause the conveyor to move the plane backward. That means there is a point of equilibrium. The thrust translates to wheel speed on a runway. That speed on a conveyor is cancelled.

That's the sticking point between ideal theoretical condition and reality. You either grant that the wheel bearings are truly frictionless as is the spirit of the question, or you get caught up on a conveyor that slowly increases speed to overcome the resting inertia of the plane, when the problem is more like yanking a tablecloth out from under plates.

[lrobe22]

Simple. Airspeed (indicated … actual…) is all that matters. If a plane in a given configuration requires 120 knots to provide enough lift for takeoff , you need 120 knots airflow across the wing. That’s why speed is measured in different ways.
Indicated
Calibrated
True
Ground

[A/E]

Inertia and Astro Physics with Jet Propulsion and Jet Fuel which is just Glorified Diesel . .

Stale Peanuts ~ Tiny Liquor Bottles ~ Small Cramped Seats ~ Blue Liquid in the On Board Outhouse

Seat Belt Technology from a '72 Pinto

Homo Stewardesses

Obese Fuggars Spilling Over the 3/4" Wide Armrest into yer Seat Space

Times ( X ) MC Squared Divided by / Milage Points Per Flight = Answer to whatever the Fuq dis Tread be about

U R Welcome

[vettemed]

Inertia and Astro Physics with Jet Propulsion and Jet Fuel which is just Glorified Diesel . .

Stale Peanuts ~ Tiny Liquor Bottles ~ Small Cramped Seats ~ Blue Liquid in the On Board Outhouse

Seat Belt Technology from a '72 Pinto

Homo Stewardesses

Obese Fuggars Spilling Over the 3/4" Wide Armrest into yer Seat Space

Times ( X ) MC Squared Divided by / Milage Points Per Flight = Answer to whatever the Fuq dis Tread be about

U R Welcome


Don't forget Rayshawnda goin' off on dat Spirit airlines employee

[A/E]

Important Factor into the Equation

Rayshawnda also Didn't Flush the Blue Fluid Surprise she left in the Stainless Steel Bowl inside the On Board Out House ~

The Waffing Aromas were not part of the Equation ~

Also . .

The Pre-Board Wheel Chair Scammers on Southwest are Related to Rayshawnda which means she boards with her GrandMammy before Southwest Rapid Rewards Members who paid $15 to Upgrade their Seating Position to A15 or Better

[Vandelay Industries]

This thread makes Daniel Bernoulli cry.

:waiting:

[vettemed]

I run on a treadmill all the time, never became airborne.



You also don't have a jet engine coming out of your ass. Probably.

[The_Dude]

Six

[Steve_R]

Six

24 :slap:

[jw38]

Important Factor into the Equation

Rayshawnda also Didn't Flush the Blue Fluid Surprise she left in the Stainless Steel Bowl inside the On Board Out House ~

The Waffing Aromas were not part of the Equation ~

Also . .

The Pre-Board Wheel Chair Scammers on Southwest are Related to Rayshawnda which means she boards with her GrandMammy before Southwest Rapid Rewards Members who paid $15 to Upgrade their Seating Position to A15 or Better

* $40

[RedLS1GTO]

It will take off. It's not a debate. It's physics.

Wheel speed has absolutely nothing to do with an aircraft flying.

[slewfoot]

Isaac Newton.

[Loco Vette]

I argued that once you apply thrust (pushing the model) you have created a differential between the conveyor speed and the wheel speed, which according to the question posed, are always a match in the opposite direction. Therefore, applying a push to the model, also requires and equal increase in opposition from the conveyor. In a static position, there is no airflow or pressure differential over the wings, and therefore no lift.

Emphasized section takes the question out of the realm of physics into the realm of magic, where anything can happen and therefore all answers to this question are correct.

[slewfoot]

It will take off. It's not a debate. It's physics.

Wheel speed has absolutely nothing to do with an aircraft flying.


Or Speed of the aircraft along with planes mounted with skis.

Don't forget the 5 different measurements of Indicated, True, Ground, Calibrated & Mach


:D

[Frankie the Fink]

It will take off. It's not a debate. It's physics.

Wheel speed has absolutely nothing to do with an aircraft flying.

So. No wheels needed. Who knew?

[RedLS1GTO]

So. No wheels needed. Who knew?

Everybody who has ever flown a self propelled aircraft, going back to the very first time with the Wright Brothers?

https://spacecenter.org/wp-content/uploads/2019/12/206311main_wright_brothers_full-1024x637.jpg

[Mick]

It will take off. It's not a debate. It's physics.

Wheel speed has absolutely nothing to do with an aircraft flying.

Well, in this case, the wheel speed does have an effect. The only force the treadmill is facing to keep the airplane from moving forward is the rolling resistance of the wheels, since we are assuming that the treadmill succeeds in keeping the plane stationary, so there is not air resistance of the body/wings of the plane to overcome.

If there is no airflow over the wings, there is no lift, so it does not take off.

[RedLS1GTO]

...since we are assuming that the treadmill succeeds in keeping the plane stationary.

Who is "we"?

That's not an "assumption". It's an incorrect statement. A treadmill won't keep it stationary. The forward movement of the aircraft relative to air has absolutely nothing to do with the wheels outside of the minimal amount of rolling resistance generated.

Because physics.

[Unsuspicious]

assuming that the treadmill succeeds in keeping the plane stationary

This is the bad assumption.
A treadmill can keep a car stationary by matching its wheel speed like on a dyno because the wheels are the source of thrust.
You would need a wind tunnel to keep a thrusting plane stationary, because the source of thrust is against the air, not ground. (And a stationary plane in a wind tunnel takes off just fine)

No friction between the plane's wheels and the plane is like asking if a car with a perfectly frictionless body can be moved by blowing air at it.

[lrobe22]

This is the bad assumption.
A treadmill can keep a car stationary by matching its wheel speed like on a dyno because the wheels are the source of thrust.
You would need a wind tunnel to keep a thrusting plane stationary, because the source of thrust is against the air, not ground. (And a stationary plane in a wind tunnel takes off just fine)

No friction between the plane's wheels and the plane is like asking if a car with a perfectly frictionless body can be moved by blowing air at it.

I’ve flown with a Pilot prankster that had his passengers “push start” the fuselage of the helicopter.

[RedLS1GTO]

You would need a wind tunnel to keep a thrusting plane stationary, because the source of thrust is against the air, not ground.

But what if you have a treadmill moving forward in a wind tunnel? :leaving:

[Unsuspicious]

Can Heather Graham on rollerskates pull herself forward with a rope if she was on a treadmill moving in the opposite direction?

https://imgix.bustle.com/uploads/image/2021/4/22/84b2d9a1-2057-41f2-9810-f6e25b042922-5885055ah.jpg?w=414&h=736&fit=crop&crop=focalpoint&fp-x=0.5038759689922481&fp-y=0.18138424821002386&dpr=2

(Yes)

[The_Dude]

24 :slap:

https://www.youtube.com/watch?v=iUAYeN3Rp2E

[GTOguy]

Good grief- you know why they tested at Kitty Hawk instead of Ohio ?

Cuz they wanted Yadkin's license plates to say 'First In Flight'?:leaving:

[Burro (He/Haw)]

Heather Graham

https://imgix.bustle.com/uploads/image/2021/4/22/84b2d9a1-2057-41f2-9810-f6e25b042922-5885055ah.jpg?w=414&h=736&fit=crop&crop=focalpoint&fp-x=0.5038759689922481&fp-y=0.18138424821002386&dpr=2

(Yes)

I’d rip into her ass like a $50.00 Taco Bell order.

[RedLS1GTO]

Good grief- you know why they tested at Kitty Hawk instead of Ohio ?

Yea. I do.

I also know why a treadmill won't stop an aircraft from flying. :shrug:

[Loco Vette]

Well, in this case, the wheel speed does have an effect. The only force the treadmill is facing to keep the airplane from moving forward is the rolling resistance of the wheels, since we are assuming that the treadmill succeeds in keeping the plane stationary, so there is not air resistance of the body/wings of the plane to overcome.

If there is no airflow over the wings, there is no lift, so it does not take off.

Bolded - Which is also the only resistance the thrust of the airplane has to overcome before it starts moving forward through the air and generating both lift and resistance.

since we are assuming that the treadmill succeeds in keeping the plane stationary,

How? Magic? If so this whole discussion is moot.

[Vandelay Industries]

What if the treadmill is facing backwards on the back of a truck going backwards through a wind tunnel that's generating air flow that's half the speed of the truck?

[RedLS1GTO]

TRUTH. If you run on a treadmill and it has an unlimited speed capacity you can run like hell you still won’t run off the front of the machine Duh.

1.) When a person is running (on a treadmill or otherwise), where does the forward force come from and where on the person is it applied?

Conversely, what is providing the "equal and opposite" force?

2.) When a jet aircraft is being propelled forward, where does the forward force come from and where on the aircraft is it applied?

Conversely, what is providing the "equal and opposite" force?


Answer those questions correctly and you will have the explanation as to why a treadmill wouldn't prevent a jet from taking off. :seasix:


Again, this is not a debate. It's not a question. It's basic physics.

[RedLS1GTO]

Thought better of that deleted post? :rofl:

[RedLS1GTO]

Just to clarify, it is really the argument of some that if you put a treadmill under this, it would... sit still with the wheels spinning?

https://imgproc.airliners.net/photos/airliners/3/1/7/0339713.jpg?v=v40

https://i.ytimg.com/vi/lpGXLOm4b80/maxresdefault.jpg

OK then. :leaving:

[KenHorse]

It will take off. It's not a debate. It's physics.

Wheel speed has absolutely nothing to do with an aircraft flying.

Bingo

It's all about airflow over the wings and control surfaces.

(did MythBusters really do a segment on this one? Seems like kindergarten stuff)

[Mick]

Bingo

It's all about airflow over the wings and control surfaces.

(did MythBusters really do a segment on this one? Seems like kindergarten stuff)

But if the action of the treadmill on the wheels holds the plane stationary relative to the ground, where does the airflow over the wings come from?

[Mick]

Who is "we"?

That's not an "assumption". It's an incorrect statement. A treadmill won't keep it stationary. The forward movement of the aircraft relative to air has absolutely nothing to do with the wheels outside of the minimal amount of rolling resistance generated.

Because physics.

The whole premise of the problem is that the treadmill prevents the airplane from moving forward relative to the ground. Once we violate that premise, yes, the whole problem is trivial. If the treadmill CAN NOT stop the plane from moving forward, then of course, the plane will hop off the treadmill in a few seconds, and then it will continue moving forward just like a regular take-off.

[Loco Vette]

But if the action of the treadmill on the wheels holds the plane stationary relative to the ground
That's the part that doesn't happen with physics.

[Unsuspicious]

The whole premise of the problem is that the treadmill prevents the airplane from moving forward relative to the ground. Once we violate that premise, yes, the whole problem is trivial. If the treadmill CAN NOT stop the plane from moving forward, then of course, the plane will hop off the treadmill in a few seconds, and then it will continue moving forward just like a regular take-off.

Nah, your misunderstanding of the problem is literally distilled down to answering "can a plane take off without moving forward" as if that is what people are arguing about.

The premise isn't that the treadmill prevents the plane moving, the problem itself is literally asking CAN the treadmill prevent the plane from moving. (It can't. You assume it can and start your arguments after that bad premise.)

[Vandelay Industries]

This is great.

120475

[dvarapala]

I myself consulted ChatGPT which claims the plain will take off.

ChatGPT also says the answer is 6, so be sure to take that into consideration. :D

[dvarapala]

It will take off. It's not a debate. It's physics.


:yesnod:

YORCk1BN7QY
xUjcHW7SHaI

[Mick]

Nah, your misunderstanding of the problem is literally distilled down to answering "can a plane take off without moving forward" as if that is what people are arguing about.

I disagree. If the plane can simply hop off the treadmill in the first 2 seconds, we don't even have a discussion.

The premise isn't that the treadmill prevents the plane moving, the problem itself is literally asking CAN the treadmill prevent the plane from moving. (It can't. You assume it can and start your arguments after that bad premise.)

I don't agree with this either. First, if we assume "frictionless wheels", then of course this is true, but I don't think there is any such thing as frictionless wheels.

Second: I've played some with radio-controlled airplanes. Some of the smaller/cheaper models BARELY have enough power to get airborne, and they come with some pretty shitty wheels that are VERY far from frictionless. I've never tried it, but it doesn't seem like it would take much treadmill velocity to hold those cheap pieces of shit from moving forward to me.

If we limit ourselves to just F-16s or some shit, then I agree, a treadmill has no chance of stopping it from moving forward.

[Loco Vette]

First, if we assume "frictionless wheels", then of course this is true, but I don't think there is any such thing as frictionless wheels.
Since this is a real world discussion, I must point out that frictionless wheels don't exist and were never part of the question. All the wheel friction (and for that matter, wind and rolling resistance does) is up the thrust required to generate enough airflow over the wings for lift.
Second: I've played some with radio-controlled airplanes. Some of the smaller/cheaper models BARELY have enough power to get airborne, and they come with some pretty shitty wheels that are VERY far from frictionless. I've never tried it, but it doesn't seem like it would take much treadmill velocity to hold those cheap pieces of shit from moving forward to me.
So you just proved my response to your first point. Enough thrust must be available to overcome whatever resistance is in the system.

[lrobe22]

Everyone’s talking about spinning wheels but nobody is talking about tires. Planes use tires.

[lrobe22]

Since this is a real world discussion, I must point out that frictionless wheels don't exist and were never part of the question. All the wheel friction (and for that matter, wind and rolling resistance does) is up the thrust required to generate enough airflow over the wings for lift. So you just proved my response to your first point. Enough thrust must be available to overcome whatever resistance is in the system.

False on “wind resistance”. A static wing with 10 knots of headwind equals 10 knots of indicated airspeed.

[Mick]

So you just proved my response to your first point. Enough thrust must be available to overcome whatever resistance is in the system.

So then, you agree that if the plane DOES NOT have enough thrust to move itself forward relative to the treadmill, then the plane DOES NOT take off. Right?

Because THAT is my point.

[Mick]

Here is another one that confounds tons of folks on long distance running forums related to doing workouts on a treadmill:

Say you have a train that is 8 miles long, but is only one car. Said another way, it is an 8 mile long tube that can roll down the railroad track. It has a floor for a runner to run on, and windows on the sides so that observers beside the track can see inside.

The train starts rolling Southbound at 8 miles an hour. After a few minutes, when everything has reached a steady state, a guy standing at the South end of the train starts running North at 8 miles per hour. Just as he is starting, you are standing by the track, and see him running, but he is perfectly stationary relative to the ground. Now:

Is he expending (more, less, the same) energy per minute than a guy running by you on the ground at 8 miles per hour?

Is he experiencing (more, less, the same) air resistance than someone running by you on the ground at 8 miles per hour?

When he runs the length of the train, will he have had a(n) (easier, harder, the same intensity) workout than the guy who ran by you on the ground doing 8 miles in an hour?

[Mick]

:yesnod:

YORCk1BN7QY
xUjcHW7SHaI

Proved nothing. The plane was obviously moving at a much higher velocity to the right than the cloth was moving to the left.

Again, if we allow the plane to move relative to the ground, the problem is trivial: Of course the plane will take off.

[The_Dude]

Everyone’s talking about spinning wheels but nobody is talking about tires. Planes use tires.

https://www.youtube.com/watch?v=SFEewD4EVwU

[Loco Vette]

False on “wind resistance”. A static wing with 10 knots of headwind equals 10 knots of indicated airspeed.

I was talking about the resitance encountered by the wheels moving through the air.

[Loco Vette]

So then, you agree that if the plane DOES NOT have enough thrust to move itself forward relative to the treadmill, then the plane DOES NOT take off. Right?

Because THAT is my point.

If a plane does not have enough thrust to generate airflow over the wings sufficient to lift the plane, it will not take off under any circumstances, treadmill or not. Any plane that can take off from a static runway can take off from this treadmill setup.

[lrobe22]

I was talking about the resitance encountered by the wheels moving through the air.

The wheels cause very little drag because they’re inside the tires. :)

[Mick]

If a plane does not have enough thrust to generate airflow over the wings sufficient to lift the plane, it will not take off under any circumstances, treadmill or not.

I agree.

Any plane that can take off from a static runway can take off from this treadmill setup.

What treadmill setup? You are making an assumption that there is no treadmill that can stop a single airplane from moving forward. Like I said, if we are talking about F-16s and shit, I agree. If we are talking about small aircraft with relatively low power to weight ratios, I'm not ready to knee jerk to that assumption.

[Unsuspicious]

If a plane is moving at 50mph relative to the ground, and the conveyor is moving 50mph in the opposite direction, then the wheels would show 100mph if the plane had a speedometer for the wheels. Big whoop, it takes off.

[Vandelay Industries]

If a plane is moving at 50mph relative to the ground, and the conveyor is moving 50mph in the opposite direction, then the wheels would show 100mph if the plane had a speedometer for the wheels. Big whoop, it takes off.

120480

[RedLS1GTO]

What treadmill setup? You are making an assumption that there is no treadmill that can stop a single airplane from moving forward. Like I said, if we are talking about F-16s and shit, I agree. If we are talking about small aircraft with relatively low power to weight ratios, I'm not ready to knee jerk to that assumption.

What force caused by a treadmill is going to stop a plane? The only forces you are introducing are the friction between the tires and the treadmill and whatever internal friction the hub assemblies have. Both of which are multiple orders of magnitude less than the overall forces in the system as a whole. That’s it. Nothing else.

Again. This is very basic physics. :skep:

[The_Dude]

https://www.youtube.com/watch?v=-35W_FWCT9Q

[The_Dude]

https://www.youtube.com/watch?v=XrzVpvtsFf0

[Steve_R]

:popcorns:

[MadInNc]

Waiting for cliffs

[John E]

https://www.youtube.com/watch?v=SFEewD4EVwU

Sang that in 5th or 6th chorus. Also sang this one...
https://www.bing.com/videos/riverview/relatedvideo?q=Aquarius+-+5th+dimension&mid=A0FBE5325925ABE46AC6A0FBE5325925ABE46AC6&FORM=VIRE

Probably because Florence was a local! Imagine if it was Aquarius - Let the Son shine in! Good music era Dude.
ps. we gotta talk before you start the bp meds if it's not too late!

[The_Dude]

Sang that in 5th or 6th chorus. Also sang this one...
https://www.bing.com/videos/riverview/relatedvideo?q=Aquarius+-+5th+dimension&mid=A0FBE5325925ABE46AC6A0FBE5325925ABE46AC6&FORM=VIRE

Probably because Florence was a local! Imagine if it was Aquarius - Let the Son shine in! Good music era Dude.
ps. we gotta talk before you start the bp meds if it's not too late!
I've been taking them for about 6 weeks now.

[John E]

I've been taking them for about 6 weeks now.

:faint: Wish I'd written sooner. message sent. :cert:

[RedLS1GTO]

Waiting for cliffs

Here ya go:

Phiziks be hard.

[Loco Vette]

I argued that once you apply thrust (pushing the model) you have created a differential between the conveyor speed and the wheel speed, which according to the question posed, are always a match in the opposite direction. Therefore, applying a push to the model, also requires and equal increase in opposition from the conveyor. In a static position, there is no airflow or pressure differential over the wings, and therefore no lift.

Emphasized section takes the question out of the realm of physics into the realm of magic, where anything can happen and therefore all answers to this question are correct.


What treadmill setup? You are making an assumption that there is no treadmill that can stop a single airplane from moving forward. I am doing no such thing. The only force applied by the treadmill to the plane in opposition to the thrust is the friction associated with rotating the landing gear, which is negligible. Any plane capable of taking off into a mild headwind can overcome that.

[Unsuspicious]

What treadmill setup? You are making an assumption that there is no treadmill that can stop a single airplane from moving forward.

Because it's a correct assumption. There is no way any treadmill that matches the plane's speed can prevent ANY plane with wheels from moving forward.

I don't think you even need wheels- a damn seaplane on a treadmill will break the friction. You don't need a fighter jet. What you need for your belief to work is if the plane is bolted down to the treadmill.

[A/E]

120585

But when we Factor in Short Orange Polyester Shorts and Pantyhose with the Cotton Panel ~

Divided by the Nautical Miles from Gary Indiana Air Port to all Routes Flown by H(o)(o)ters Air . . .

120586

You get some just " OK " Wings that all short a feels bit Slighted Purchasing due to the Lack of Bare Skin on the Legs, ~

But the Push Up Bras and Camel Toes can Compensate for any Feelings of Regret

X 3.14 - Mc Squared

[Vette40th]

Same thing with speed of light. Turn your lights on at the speed of light, will the light travel faster? Radio waves travel at the speed of light, so would making a transmission to something in front of your vessel going the speed of light make it faster?

[Unsuspicious]

Same thing with speed of light. Turn your lights on at the speed of light, will the light travel faster? Radio waves travel at the speed of light, so would making a transmission to something in front of your vessel going the speed of light make it faster?

Anything with mass can't travel at the speed of light, so anything making or receiving signals would be slower