That plane, and it taking off.

[NanoStuff]

The linear speed of the belt is determined by the linear speed of the car (or plane). So the belt will only move backwards if the object moves forwards. Same as with the plane. The only reason the belt moves backwards in the first place is because the plane is moving forwards.

If the linear speed of the car is 1MPH and the belt is 1MPH in reverse, the wheels are rotating at 2MPH, therefore there's 1MPH forward velocity

 

[PurdueRy]

Originally posted by: NanoStuff
The linear speed of the belt is determined by the linear speed of the car (or plane). So the belt will only move backwards if the object moves forwards. Same as with the plane. The only reason the belt moves backwards in the first place is because the plane is moving forwards.

If the linear speed of the car is 1MPH and the belt is 1MPH in reverse, the wheels are rotating at 2MPH, therefore there's 1MPH forward velocity

I see your point....hmm...I guess the belt would have to match the speed on the speedometer of the car. THEN it would stay in place.

 

[AlienCraft]

Originally posted by: PurdueRy

Originally posted by: AlienCraft

Originally posted by: D1gger

Originally posted by: LoKe

Originally posted by: msparish

Originally posted by: LoKe
Then can someone explain this to me real quick? I don't feel like digging in the other thread :

If the plane and conveyor are moving at the exact same speed, meaning, the plane isn't moving, is air still being moved?

The plane still moves, despite the conveyor belt. A plane doesn't get its thrust through the wheels. The wheels will just be rotating at twice their normal speed.

But I mean, if the planes wheels were matching the speed of the conveyor belt, it's practically the same as the plane being completely stationary on a cement floor. It's not actually moving, and no additional wind is being pushed under the wings.

You are working under the assumption that the wheels are what drive the plane forward, but that is simply not the case. The props or jet engine create the thrust that move the plane forward, regardless of the speed the wheels are spinning. Under your thinking, the minute a plane left the runway, and the wheels stopped spinning (which they do) the plane would fall out of the sky. Since planes do not generally fall out of the sky, it must be that the thrust comes from the engines working in the air, not the engines thrusting against the earth or the wheels providing force.

You're ignoring the effect of gravity at the inital stages of establishing thrust. Gravity is pushing down on the plane even as the wheels turn. Only when the thrust forward exceeds the friction holding it down it does it roll forward, ONLY then air is flowing over the wing.

A jet does not cause a plane to fly by sucking air across the wing. It does it by PUSHING it through the air. That push forward must greater than the force of gravity.
Since the mythical conveyor belt is able to accelerate infinitely, the plane is not rolling therefore there is ZERO airflow across the wing. No forward motion =No airflow otw. No airflow otw = no lift. No lift = no flight.

Forward motion is what gets air flowing over the wings. If that conveyor belt then starts turning in the reverse direction, gravity re-asserts as the predominate force and airflow ceases.

This is why cars (Formula1 and NASCAR) have ground effect aerodynamics calculated in so as to keep the wheels on the track. YES, once the wheels leave the ground, the lift is reduced and they come back down, but thatwsould have an oscillation adverse effect on performance.

The conveyor belt does not accelerate to infinity. We already disregarded this case as this is not the way it is predominantly posted accross the internet. It matches the speed of the PLANE. Not the rotational speed of the wheels.

Well, in that case , you're changing the stated problem to include parameters not mentioned.
In ot5her words, you're changing the problem to suit your answer.
That is not science.
\ As I understood the question, The conveyor is a perfect device capable of countering the forward motion of the plane sitting on it exactly, allowing for the effect of no forward motion. The other paramete I understood was the source of thrust was at the rear (as in a 737) so there was no direct airflow over the wings, caused by the engine.
Thus the remaining force was GRAVITY, and the crux of the question. How does a plane escape the force of gravity and fly?
Given that a JET ENGINE cannot accelerate to infinity is also disregarded.
If you're going to be loose with the "rules" you can make it say anything you want.
It still isn't science.

 

[NanoStuff]

Originally posted by: PurdueRy

Originally posted by: NanoStuff
The linear speed of the belt is determined by the linear speed of the car (or plane). So the belt will only move backwards if the object moves forwards. Same as with the plane. The only reason the belt moves backwards in the first place is because the plane is moving forwards.

If the linear speed of the car is 1MPH and the belt is 1MPH in reverse, the wheels are rotating at 2MPH, therefore there's 1MPH forward velocity

I see your point....hmm...I guess the belt would have to match the speed on the speedometer of the car. THEN it would stay in place.

Yup, that would be it right there. In this case the belt would double it's speed to match the angular velocity, or the rotational speed of the wheel, so the car sits still.

Furthermore, this again shows that no crazy 'infinite acceleration' phenomenon would take place if the belt attempted to match the rotation of the wheel. It simply means the belt would move in reverse twice as fast as in the original case. And again the confusion is perfectly understood as the belt would first have to 'see' the wheel begin to rotate to match it, so there is a timing delay here in the real world as you'd expect. But in the real world the belt could easily compensate for this initial examination and the end result would still be the same... so either it's only theoretical or some basic assumptions should be made.

 

[PurdueRy]

Originally posted by: AlienCraft

Originally posted by: PurdueRy

Originally posted by: AlienCraft

Originally posted by: D1gger

Originally posted by: LoKe

Originally posted by: msparish

Originally posted by: LoKe
Then can someone explain this to me real quick? I don't feel like digging in the other thread :

If the plane and conveyor are moving at the exact same speed, meaning, the plane isn't moving, is air still being moved?

The plane still moves, despite the conveyor belt. A plane doesn't get its thrust through the wheels. The wheels will just be rotating at twice their normal speed.

But I mean, if the planes wheels were matching the speed of the conveyor belt, it's practically the same as the plane being completely stationary on a cement floor. It's not actually moving, and no additional wind is being pushed under the wings.

You are working under the assumption that the wheels are what drive the plane forward, but that is simply not the case. The props or jet engine create the thrust that move the plane forward, regardless of the speed the wheels are spinning. Under your thinking, the minute a plane left the runway, and the wheels stopped spinning (which they do) the plane would fall out of the sky. Since planes do not generally fall out of the sky, it must be that the thrust comes from the engines working in the air, not the engines thrusting against the earth or the wheels providing force.

You're ignoring the effect of gravity at the inital stages of establishing thrust. Gravity is pushing down on the plane even as the wheels turn. Only when the thrust forward exceeds the friction holding it down it does it roll forward, ONLY then air is flowing over the wing.

A jet does not cause a plane to fly by sucking air across the wing. It does it by PUSHING it through the air. That push forward must greater than the force of gravity.
Since the mythical conveyor belt is able to accelerate infinitely, the plane is not rolling therefore there is ZERO airflow across the wing. No forward motion =No airflow otw. No airflow otw = no lift. No lift = no flight.

Forward motion is what gets air flowing over the wings. If that conveyor belt then starts turning in the reverse direction, gravity re-asserts as the predominate force and airflow ceases.

This is why cars (Formula1 and NASCAR) have ground effect aerodynamics calculated in so as to keep the wheels on the track. YES, once the wheels leave the ground, the lift is reduced and they come back down, but thatwsould have an oscillation adverse effect on performance.

The conveyor belt does not accelerate to infinity. We already disregarded this case as this is not the way it is predominantly posted accross the internet. It matches the speed of the PLANE. Not the rotational speed of the wheels.

Well, in that case , you're changing the stated problem to include parameters not mentioned.
In ot5her words, you're changing the problem to suit your answer.
That is not science.
\ As I understood the question, The conveyor is a perfect device capable of countering the forward motion of the plane sitting on it exactly, allowing for the effect of no forward motion. The other paramete I understood was the source of thrust was at the rear (as in a 737) so there was no direct airflow over the wings, caused by the engine.
Thus the remaining force was GRAVITY, and the crux of the question. How does a plane escape the force of gravity and fly?
Given that a JET ENGINE cannot accelerate to infinity is also disregarded.
If you're going to be loose with the "rules" you can make it say anything you want.
It still isn't science.

Listen dude,

The OP already specified that he made an error in wording. The problem as it is stated around the internet is as follows:

A plane is standing on a runway that can move (like a giant conveyor
belt). This conveyor has a control system that tracks the plane's
speed and tunes the speed of the conveyor to be exactly the same (but
in the opposite direction).

Will the plane be able to take off?

This is the question that you should answer

 

[PurdueRy]

Originally posted by: NanoStuff

Originally posted by: PurdueRy

Originally posted by: NanoStuff
The linear speed of the belt is determined by the linear speed of the car (or plane). So the belt will only move backwards if the object moves forwards. Same as with the plane. The only reason the belt moves backwards in the first place is because the plane is moving forwards.

If the linear speed of the car is 1MPH and the belt is 1MPH in reverse, the wheels are rotating at 2MPH, therefore there's 1MPH forward velocity

I see your point....hmm...I guess the belt would have to match the speed on the speedometer of the car. THEN it would stay in place.

Yup, that would be it right there. In this case the belt would double it's speed to match the angular velocity, or the rotational speed of the wheel, so the car sits still.

Furthermore, this again shows that no crazy 'infinite acceleration' phenomenon would take place if the belt attempted to match the rotation of the wheel. It simply means the belt would move in reverse twice as fast as in the original case.

eh, I still think that's not entirely correct. In the car example. The treadmill if it matched the speed on the speedometer is matching the LINEAR speed the car WOULD be traveling if it wasn't on the treadmill. It is not matching the rotational velocity. Yet the car would stay still. So I think there is still a error in wording if you specify the problem to meet the rotational speed of the wheels.

For instance, if the plane had its wheels spinning at 30 MPH then the belt would change to 30...but then the wheels would spin at 60...the belt would change to 60...but then your at 120...as you can see this is the infinite case everyone is talking about.

 

[AlienCraft]

Originally posted by: PurdueRy
[
Listen dude,

The OP already specified that he made an error in wording. The problem as it is stated around the internet is as follows:

A plane is standing on a runway that can move (like a giant conveyor
belt). This conveyor has a control system that tracks the plane's
speed and tunes the speed of the conveyor to be exactly the same (but
in the opposite direction).

Will the plane be able to take off?

This is the question that you should answer

No, because if it's matching the foward vector with a revers vector the net is zero foward motion. A wing relies on the forward motion of the body its attached to provide the pressure differential that results in lift. Without lift, it's not flying.

This is why when the headwind force confronting a propellor driven plane reaches the maximum speed capability of that plane, they cease to move forward and WILL STALL. That isn't flying either. dude.
Jets rarely have that problem, in natural flight, as they are capable of speeds far exceeding even the most "perfect storm". However when flying through the wake of another JET AIRCRAFT, that airflow can be disturbed enough to cause loss of lift resulting in flat spins. As an additional effect of that loss of air pressure that jet engines need to operate is they can be extinguished in flight. Jets don't work in negative air pressure or Vacuums. Those would be ROCKETS.
And if you'll recall that scene in "Top Gun" where "Maverick" looses "Goose", that isn't flying either, dude.

 

[NanoStuff]

Originally posted by: PurdueRy

Originally posted by: NanoStuff

Originally posted by: PurdueRy

Originally posted by: NanoStuff
The linear speed of the belt is determined by the linear speed of the car (or plane). So the belt will only move backwards if the object moves forwards. Same as with the plane. The only reason the belt moves backwards in the first place is because the plane is moving forwards.

If the linear speed of the car is 1MPH and the belt is 1MPH in reverse, the wheels are rotating at 2MPH, therefore there's 1MPH forward velocity

I see your point....hmm...I guess the belt would have to match the speed on the speedometer of the car. THEN it would stay in place.

Yup, that would be it right there. In this case the belt would double it's speed to match the angular velocity, or the rotational speed of the wheel, so the car sits still.

Furthermore, this again shows that no crazy 'infinite acceleration' phenomenon would take place if the belt attempted to match the rotation of the wheel. It simply means the belt would move in reverse twice as fast as in the original case.

eh, I still think that's not entirely correct. In the car example. The treadmill if it matched the speed on the speedometer is matching the LINEAR speed the car WOULD be traveling if it wasn't on the treadmill. It is not matching the rotational velocity. Yet the car would stay still. So I think there is still a error in wording if you specify the problem to meet the rotational speed of the wheels.

For instance, if the plane had its wheels spinning at 30 MPH then the belt would change to 30...but then the wheels would spin at 60...the belt would change to 60...but then your at 120...as you can see this is the infinite case everyone is talking about.

Ah yes. But if the wheels are spinning at 30MPH and the belt has to accelerate or 'change' to match that speed, that means the belt wasn't moving at 30MPH in the first place, which negates the static condition that the belt always matches the rotation of the wheels. If the wheels are spinning faster than the belt at any point, this condition breaks the rules of that particular question. If however the wheels are spinning at 30MPH and the belt is already moving backwards at 30MPH, the belt does not need to accelerate therefore it does not speed up the wheels.

So if the speedometer is showing 30MPH, the wheels are rotating at 30MPH, the belt is moving backwards at 30MPH and the car sits still.

And then if the car accelerates to 45MPH, the belt accelerates at exactly the same speed so that the belt never has to 'accelerate' to the speed of the wheels because it's always going at the speed of the wheels. (rotation that is)

 

[PurdueRy]

Originally posted by: AlienCraft

Originally posted by: PurdueRy
[
Listen dude,

The OP already specified that he made an error in wording. The problem as it is stated around the internet is as follows:

A plane is standing on a runway that can move (like a giant conveyor
belt). This conveyor has a control system that tracks the plane's
speed and tunes the speed of the conveyor to be exactly the same (but
in the opposite direction).

Will the plane be able to take off?

This is the question that you should answer

No, because if it's matching the foward vector with a revers vector the net is zero foward motion. A wing relies on the forward motion of the body its attached to provide the pressure differential that results in lift. Without lift, it's not flying.

This is why when the headwind force confronting a propellor driven plane reaches the maximum speed capability of that plane, they cease to move forward and WILL STALL. That isn't flying either. dude.
Jets rarely have that problem, in natural flight, as they are capable of speeds far exceeding even the most "perfect storm". However when flying through the wake of another JET AIRCRAFT, that airflow can be disturbed enough to cause loss of lift resulting in flat spins. As an additional effect of that loss of air pressure that jet engines need to operate is they can be extinguished in flight. Jets don't work in negative air pressure or Vacuums. Those would be ROCKETS.
And if you'll recall that scene in "Top Gun" where "Maverick" looses "Goose", that isn't flying either, dude.

You assume the treadmill can keep the plane stationary. However, this is an inaccurate conception. You can read ALL the posts in both threads to see exactly why...however I will give you the quick explanation.

Engine causes force on planes BODY. Treadmill causes force on planes wheel. Treadmill cannot counter force on planes body due to being in a completely different system. Plane rolls forward. Plane takes off.

Like I said, read the both threads and you will get some practical examples such as:

Take a toy car, set it on a treadmill slanted downwards. The force of gravity in this case represents the same force the engines would apply. Turn on treadmill...place car on treadmill...turn treadmill speed up as fast as you want...car rolls forward...note this is a toy car and not a real car as in a toy car the wheels are free to spin.

Think this example is unfair? Draw the FBD and tell me how the situations are any different.

 

[PurdueRy]

Originally posted by: NanoStuff

Originally posted by: PurdueRy

Originally posted by: NanoStuff

Originally posted by: PurdueRy

Originally posted by: NanoStuff
The linear speed of the belt is determined by the linear speed of the car (or plane). So the belt will only move backwards if the object moves forwards. Same as with the plane. The only reason the belt moves backwards in the first place is because the plane is moving forwards.

If the linear speed of the car is 1MPH and the belt is 1MPH in reverse, the wheels are rotating at 2MPH, therefore there's 1MPH forward velocity

I see your point....hmm...I guess the belt would have to match the speed on the speedometer of the car. THEN it would stay in place.

Yup, that would be it right there. In this case the belt would double it's speed to match the angular velocity, or the rotational speed of the wheel, so the car sits still.

Furthermore, this again shows that no crazy 'infinite acceleration' phenomenon would take place if the belt attempted to match the rotation of the wheel. It simply means the belt would move in reverse twice as fast as in the original case.

eh, I still think that's not entirely correct. In the car example. The treadmill if it matched the speed on the speedometer is matching the LINEAR speed the car WOULD be traveling if it wasn't on the treadmill. It is not matching the rotational velocity. Yet the car would stay still. So I think there is still a error in wording if you specify the problem to meet the rotational speed of the wheels.

For instance, if the plane had its wheels spinning at 30 MPH then the belt would change to 30...but then the wheels would spin at 60...the belt would change to 60...but then your at 120...as you can see this is the infinite case everyone is talking about.

Ah yes. But if the wheels are spinning at 30MPH and the belt has to accelerate or 'change' to match that speed, that means the belt wasn't moving at 30MPH in the first place, which negates the static condition that the belt always matches the rotation of the wheels. If the wheels are spinning faster than the belt at any point, this condition breaks the rules of that particular question. If however the wheels are spinning at 30MPH and the belt is already moving backwards at 30MPH, the belt does not need to accelerate therefore it does not speed up the wheels.

So if the speedometer is showing 30MPH, the wheels are rotating at 30MPH, the belt is moving backwards at 30MPH and the car sits still.

the wheels would not rotate at 30 MPH is that case. The net speed on the wheels is 60 MPH. Speedometers do not measure rotational speed. They measure linear speed. If you change the size of the tires on your car...your speedometer will be off.

 

[NanoStuff]

Originally posted by: PurdueRy

Originally posted by: NanoStuff

Originally posted by: PurdueRy

Originally posted by: NanoStuff

Originally posted by: PurdueRy

Originally posted by: NanoStuff
The linear speed of the belt is determined by the linear speed of the car (or plane). So the belt will only move backwards if the object moves forwards. Same as with the plane. The only reason the belt moves backwards in the first place is because the plane is moving forwards.

If the linear speed of the car is 1MPH and the belt is 1MPH in reverse, the wheels are rotating at 2MPH, therefore there's 1MPH forward velocity

I see your point....hmm...I guess the belt would have to match the speed on the speedometer of the car. THEN it would stay in place.

Yup, that would be it right there. In this case the belt would double it's speed to match the angular velocity, or the rotational speed of the wheel, so the car sits still.

Furthermore, this again shows that no crazy 'infinite acceleration' phenomenon would take place if the belt attempted to match the rotation of the wheel. It simply means the belt would move in reverse twice as fast as in the original case.

eh, I still think that's not entirely correct. In the car example. The treadmill if it matched the speed on the speedometer is matching the LINEAR speed the car WOULD be traveling if it wasn't on the treadmill. It is not matching the rotational velocity. Yet the car would stay still. So I think there is still a error in wording if you specify the problem to meet the rotational speed of the wheels.

For instance, if the plane had its wheels spinning at 30 MPH then the belt would change to 30...but then the wheels would spin at 60...the belt would change to 60...but then your at 120...as you can see this is the infinite case everyone is talking about.

Ah yes. But if the wheels are spinning at 30MPH and the belt has to accelerate or 'change' to match that speed, that means the belt wasn't moving at 30MPH in the first place, which negates the static condition that the belt always matches the rotation of the wheels. If the wheels are spinning faster than the belt at any point, this condition breaks the rules of that particular question. If however the wheels are spinning at 30MPH and the belt is already moving backwards at 30MPH, the belt does not need to accelerate therefore it does not speed up the wheels.

So if the speedometer is showing 30MPH, the wheels are rotating at 30MPH, the belt is moving backwards at 30MPH and the car sits still.

the wheels would not rotate at 30 MPH is that case. The net speed on the wheels is 60 MPH

If the car does not move and the belt spins, the wheels will always rotate at the speed of the belt. The belt will not allow the car to accelerate on the belt because it always matches the rotation of the wheels, so no laws of the universe are broken.

 

[NanoStuff]

Originally posted by: PurdueRy
They measure linear speed. If you change the size of the tires on your car...your speedometer will be off.

They measure 'linear' speed if the car is on a static surface. If you take the car out for a drive on the conveyor belt, the speedometer will show the incorrect speed. (well, correct in relationship to the belt, but not the world around it). If you change the size of the tires, you'd naturally also adjust the speedometer for those tires

 

[PurdueRy]

Originally posted by: NanoStuff

If the car does not move and the belt spins, the wheels will always rotate at the speed of the belt. The belt will not allow the car to accelerate on the belt because it always matches the rotation of the wheels, so no laws of the universe are broken.

ok, I thought hard about it...and I would have to agree with this. I think the confusion comes with the transition from a plane to a car...good point however.

I would say make a new thread about that question...but...I am going to have to say NO on that

 

[AlienCraft]

Originally posted by: PurdueRy

You assume the treadmill can keep the plane stationary. However, this is an inaccurate conception. You can read ALL the posts in both threads to see exactly why...however I will give you the quick explanation.

Engine causes force on planes BODY. Treadmill causes force on planes wheel. Treadmill cannot counter force on planes body due to being in a completely different system. Plane rolls forward. Plane takes off.

Like I said, read the both threads and you will get some practical examples such as:

Take a toy car, set it on a treadmill slanted downwards. The force of gravity in this case represents the same force the engines would apply. Turn on treadmill...place car on treadmill...turn treadmill speed up as fast as you want...car rolls forward...note this is a toy car and not a real car as in a toy car the wheels are free to spin.

If this is the same example for the plane, then you've changed the example to fit your answer. And introduced other parameters such as No enginee in your toy car.
\ Please keep the parameters equal in order to discuss the problem scientifically.
AGAIN, For the record, Humor me here please.... the conveyor belt is used to eliminate the forward motion of the plane ( a 737 type w/ engine not contributing to airflow over wings).
In this example the "perfect conveyor" is capable of counteracting the effect of the planes engine so as to cause for the unnatural effect of no relative forward motion. This forward motion is required for air to flow over the wings and cause the lift we are calling flight. If, in your example, the conveyor is tilted ( and is infinitly long) to allow for gravity to cause forward motion eventually that motion will result in enough forward speed for lift and thus flight.
The key to this problem is the event moment of forward motion. Without airflow over the wings (and it is not provided by any action of the engine in this problem), there will be no lift and no flight is possible without lift.
Since gravity is what is holding us down, gravity= Da Man. And you know the rule.....
Da Man is always keepin' a brother down.

 

[NanoStuff]

Originally posted by: PurdueRy

Originally posted by: NanoStuff

If the car does not move and the belt spins, the wheels will always rotate at the speed of the belt. The belt will not allow the car to accelerate on the belt because it always matches the rotation of the wheels, so no laws of the universe are broken.

ok, I thought hard about it...and I would have to agree with this. I think the confusion comes with the transition from a plane to a car...good point however.

I would say make a new thread about that question...but...I am going to have to say NO on that

Heh, no way I don't want to tear ATOT apart on my first week.

The plane/car thing is a tough barrier to get your mind across, confused the hell out of me the first time I saw the question too. I knew the plane would take off but even so I didn't understand exactly how, or what it would require for the plane to NOT take off. After a good night's sleep I put a car on this imaginary conveyor belt and realized that it doesn't matter what is attached to the wheels or what is pushing them forward. The only thing that mattered is the rotation of the wheels and/or translational velocity, and then it all became remarkably obvious.

It really is a fascinating problem

 

[WHAMPOM]

Originally posted by: blahblah99

Originally posted by: 91TTZ

Originally posted by: deathkoba


The plane will take off only if it's engine can generate enough thrust to push the plane even harder than it already is doing, (which is what's keeping it visually stationary in the first place) to the point where there is enough airspeed for take off. So the real answer is YES or NO depending on the performance of the engine and how fast that conveyor belt is moving and whether or not the conveyor belt is adjusting it's speed in realtime as the plane's engine makes adjustments. That plus other environmental factors that affect flight performance directly or indirectly. It's common sense folks.

For the most part, it doesn't matter what the belt is doing, since the plane is just rolling.

My previous example was taken to the extreme, and isn't realistic.

If a jet's takeoff speed is 200 mph, and the belt is moving backwards at 200 mph, the plane will still take off just as easily. The only difference will be that the wheels will be turning at 400 mph.

Bingo! Why is that so hard to comprehend for some people?

some people can add -200 + 200 = 0 movement. that plane is essentially sitting there with its' brakes on and engines running. It must reach a critical AIR-speed to acquire lift and so called "take off". All you are doing is confusing ground-speed and air-speed. You won't fly in 100mph winds unless in a high altitude Jet Stream. But take a plane with a top speed of 95mph and head wind of 100mph, you will be on a conveyor of air moving you backwards at 5mph.

 

[PurdueRy]

Originally posted by: AlienCraft

Originally posted by: PurdueRy

You assume the treadmill can keep the plane stationary. However, this is an inaccurate conception. You can read ALL the posts in both threads to see exactly why...however I will give you the quick explanation.

Engine causes force on planes BODY. Treadmill causes force on planes wheel. Treadmill cannot counter force on planes body due to being in a completely different system. Plane rolls forward. Plane takes off.

Like I said, read the both threads and you will get some practical examples such as:

Take a toy car, set it on a treadmill slanted downwards. The force of gravity in this case represents the same force the engines would apply. Turn on treadmill...place car on treadmill...turn treadmill speed up as fast as you want...car rolls forward...note this is a toy car and not a real car as in a toy car the wheels are free to spin.

If this is the same example for the plane, then you've changed the example to fit your answer. And introduced other parameters such as No enginee in your toy car.
\ Please keep the parameters equal in order to discuss the problem scientifically.
AGAIN, For the record, Humor me here please.... the conveyor belt is used to eliminate the forward motion of the plane ( a 737 type w/ engine not contributing to airflow over wings).
In this example the "perfect conveyor" is capable of counteracting the effect of the planes engine so as to cause for the unnatural effect of no relative forward motion. This forward motion is required for air to flow over the wings and cause the lift we are calling flight. If, in your example, the conveyor is tilted ( and is infinitly long) to allow for gravity to cause forward motion eventually that motion will result in enough forward speed for lift and thus flight.
The key to this problem is the event moment of forward motion. Without airflow over the wings (and it is not provided by any action of the engine in this problem), there will be no lift and no flight is possible without lift.
Since gravity is what is holding us down, gravity= Da Man. And you know the rule.....
Da Man is always keepin' a brother down.

There is no engine in the toy car but I told you...gravity acts on the toy car in the same way. In fact this example is VERY scientific. It seems you are unwilling to draw the FBD for each example, however, as that would probably be unscientific to you too....

Sure the treadmill can rotate at the same speed as the plane moves forward...but it CANNOT slow the planes forward movement. If you would draw the FBD you would understand...

 

[PurdueRy]

Originally posted by: WHAMPOM

Originally posted by: blahblah99

Originally posted by: 91TTZ

Originally posted by: deathkoba


The plane will take off only if it's engine can generate enough thrust to push the plane even harder than it already is doing, (which is what's keeping it visually stationary in the first place) to the point where there is enough airspeed for take off. So the real answer is YES or NO depending on the performance of the engine and how fast that conveyor belt is moving and whether or not the conveyor belt is adjusting it's speed in realtime as the plane's engine makes adjustments. That plus other environmental factors that affect flight performance directly or indirectly. It's common sense folks.

For the most part, it doesn't matter what the belt is doing, since the plane is just rolling.

My previous example was taken to the extreme, and isn't realistic.

If a jet's takeoff speed is 200 mph, and the belt is moving backwards at 200 mph, the plane will still take off just as easily. The only difference will be that the wheels will be turning at 400 mph.

Bingo! Why is that so hard to comprehend for some people?

some people can add -200 + 200 = 0 movement. that plane is essentially sitting there with its' brakes on and engines running. It must reach a critical AIR-speed to acquire lift and so called "take off". All you are doing is confusing ground-speed and air-speed. You won't fly in 100mph winds unless in a high altitude Jet Stream. But take a plane with a top speed of 95mph and head wind of 100mph, you will be on a conveyor of air moving you backwards at 5mph.

See post above...if this was a car....I would agree with you...however, the treadmill has no way to slow the forward progress of the car.

Note: My shift is up...where is Mugs of Jagec?

 

[Praxis1452]

Originally posted by: Banzai042
202 with a knowledge of how things really work, and 127 that think a plane is a car.

 

[WHAMPOM]

Forward motion is counteracted, what other forces are there? A stationary plane cannot take-off.

 

[PurdueRy]

Originally posted by: WHAMPOM
Forward motion is counteracted, what other forces are there? A stationary plane cannot take-off.

counteracted by what?

The FBD will show you the force of the treadmill does not oppose the body of the plane/engines...it only spins the wheels. Therefore there is no opposing force.

 

[AlienCraft]

Originally posted by: PurdueRy

Originally posted by: AlienCraft

Originally posted by: PurdueRy

You assume the treadmill can keep the plane stationary. However, this is an inaccurate conception. You can read ALL the posts in both threads to see exactly why...however I will give you the quick explanation.

Engine causes force on planes BODY. Treadmill causes force on planes wheel. Treadmill cannot counter force on planes body due to being in a completely different system. Plane rolls forward. Plane takes off.

Like I said, read the both threads and you will get some practical examples such as:

Take a toy car, set it on a treadmill slanted downwards. The force of gravity in this case represents the same force the engines would apply. Turn on treadmill...place car on treadmill...turn treadmill speed up as fast as you want...car rolls forward...note this is a toy car and not a real car as in a toy car the wheels are free to spin.

If this is the same example for the plane, then you've changed the example to fit your answer. And introduced other parameters such as No enginee in your toy car.
\ Please keep the parameters equal in order to discuss the problem scientifically.
AGAIN, For the record, Humor me here please.... the conveyor belt is used to eliminate the forward motion of the plane ( a 737 type w/ engine not contributing to airflow over wings).
In this example the "perfect conveyor" is capable of counteracting the effect of the planes engine so as to cause for the unnatural effect of no relative forward motion. This forward motion is required for air to flow over the wings and cause the lift we are calling flight. If, in your example, the conveyor is tilted ( and is infinitly long) to allow for gravity to cause forward motion eventually that motion will result in enough forward speed for lift and thus flight.
The key to this problem is the event moment of forward motion. Without airflow over the wings (and it is not provided by any action of the engine in this problem), there will be no lift and no flight is possible without lift.
Since gravity is what is holding us down, gravity= Da Man. And you know the rule.....
Da Man is always keepin' a brother down.

There is no engine in the toy car but I told you...gravity acts on the toy car in the same way. In fact this example is VERY scientific. It seems you are unwilling to draw the FBD for each example, however, as that would probably be unscientific to you too....

Sure the treadmill can rotate at the same speed as the plane moves forward...but it CANNOT slow the planes forward movement. If you would draw the FBD you would understand...

But gravity is acting on the plane in the same way.
You are eliminating the effect of gravity by slanting the Conveyor. You are equating Gravity with the engine in the plane which is not the case. The Engine is required to overcome the resistive force of friction and cause forward motion. If the conveyor is already contering forward motion in the plane example, there is no airflow over the wing. Plenty of rotational speed at the wheels, but no forward motion. The key component is gravity which still has a downward frictional force on the wheels, regardless of their relative speed to the conveyor.
The frictional forces are reduced as the plane gains speed, moves forward and lift comes into play as more and more weight is removed from the landing gear, ultimately equaling the downward force of gravity and then exceeding it where the plane "rotates" and lifts into the air.
As long as forward thrust over the wings exceeds the downward force of gravity (including all frictional forces), flight is achieved. When forward air speed over the wings exceeds the thrust forward,[/b[ lift diminshes and flight is no longer in play. This is called the "stall speed" and has nothing to do with relative ground speed.
Until the plane leaves the ground, Relative air speed and Ground speed are the same. This is what is confusing the problem here. Since Gravity effects all objects without lifting (aerodynamic)properties in the same way, until those lifting (aerodynamic) properties are called into play, it stays on the ground. Spinning the wheels does NOTHING to change that. In the conveyor problem, the wheels are spinning like crazy, but the force of gravity still is in effect because there is NOT ENOUGH FORWARD MOTION to cause lift. If you change the problem to include a headwind that exceeds the stall speed, it will lift and then move forward realtive to the amount of thrust provided by the engine at the rear.
This is why aircraft carriers drive into the wind, and the catapult operators need to know the speed of their ship, the wind speed, and the weight of the aircraft in order to dial in the correct amount of force the catapult will deliver. Too much and they will over accelerate the forward landing gear / catapult hook right off of the aircraft, literally ripping it from the plane. Too little and it will not have enough airspeed over the wings to achieve flight before the end of the ramp.

A single engine Piper may be capable of 100 -150 mph depending on weight, engine type, etc. If the headwind is 100 MPH and the plane is only capable of 130 mph, you will have a forward vector speed ( relative Ground Speed) of 30 mph.
Your pitot tube will be measuring these air pressures and doing the differential equations that will give you a relative speed reading of 30 mph.

This is when the commercial pilots start re doing their fuel consumption calculations, start handing out free drinks and rotating out the old movies, and asking other aircraft for their wind speed / vector calcs.

 

[Suspicious-Teach8788]

Forward thrust does not need to exceed the downward force of gravity genius.

Draw a FBD and you will see. They are vectors that are orthogonal, and anyone who knows vectors knows that it doesn't matter how fast you fly, your object will drop.. unless of course you have lift. LIFT is what counteracts gravity. Oh and if you don't believe me, why don't you go try that gun example that we learn in 2D kinematics. Shoot a bullet and drop it. They fall to the ground at the same time.

How is there not enough forward motion to cause lift? The conveyor belt has absolutely no purpose at all. The problem is essentially reduced to a plane on a runway. Who cares if the runway is a conveyor belt or not, the plane works EXACTLY THE SAME.

This has nothing to do with flying into the wind, or air speed being reduced or what not. NOTHING is changed with a treadmill/conveyor belt. DO YOU READ ME AT ALL? GOOD GOD.

If your bearings are frictionless and y ou put the plane down on the conveyor belt and you spin it as fast as you can, the plane is STATIONARY as long as the engines are off. Once they are on, all you get is forward motion.

 

[CorCentral]

I will try to outline it simply:

a: If we placed an automobile on a conveyor belt and tried to accelerate, the conveyor would increase speed ( f.p.m feet per minute of the belt ) as the rpm of the wheels increased. The auto would therefore remain in the same relative position. The wheels are directly connected to the engine through the transmission, differential, etc. If the vehicle moves forward 1ft. the wheels have to follow at a fixed ratio determined by the differential & transmission and the conveyor f.p.m. would follow. Therefore if the automobile had wings, it could never advance faster than the surface speed of the conveyor belt and would never take flight.

b: An airplanes thrust is separate from the rotation of the wheels. If an airplane were in flight it would not matter if the wheels rotated faster or slower in relationship to the planes air speed or even if the wheels rotated in reverse, or even if the wheels didn't rotate at all. The flight of an airplane unlike that of an earth bound vehicle is not dependent upon frictional force to advance the plane, in this case the frictional force being a tire. The plane is powered by a jet engine or propeller to propel it forward and is not frictionally connected to the earth.

In other words, the airplane will take flight regardless of the conveyor, even if the conveyor were powered and running in reverse.

 

[AlienCraft]

Originally posted by: PurdueRy

Originally posted by: WHAMPOM
Forward motion is counteracted, what other forces are there? A stationary plane cannot take-off.

counteracted by what?

The FBD will show you the force of the treadmill does not oppose the body of the plane/engines...it only spins the wheels. Therefore there is no opposing force.

Yes, Gravity. The wheels are spinning, but without forward motion, there is no air movement across the wings.
Remember, the engine ( especially a rear mounted jet as in the original example) is not providing lift.
No air movement over the wing, be it by forward motion of the object under test, or by "wind", and there is no pressure differential to cause lift.
You can reduce rolling friction to zero, but with no forward motion, or pressure differential over a lifting body (or a rotating wing) and this is what the counter rotating conveyor is supposed to represent and it will sit there forever.
Or until you modify the problem to suit your answer.


There is no forward motion on an Automotive Dynomometer and these are engine driven wheels rotating in one direction against counter rotating wheels and the relative ground speed is accurate (for a calibrated tire diameter) on the speedo.

What is this acronym you keep using "FBD"?