You have a plane and a conveyor belt.

[rizzaz]

Originally posted by: JujuFish

Originally posted by: rizzaz
"The belt compensates for the rotation of the wheels in reverse, as in the belt moves in reverse exactly as fast as the wheels move forward"



However the planes engines can push really hard ( harder that you could push a wheelchair!) so it can keep getting faster until it runs down the runway and takes off like normal, its no different to a normal take off except that you would need a longer runway!!

Except now we have exceeded the described senario.. the planes wheels are rotating faster than the runway.
so yes the plane could take off.. except it doesn't because all the thrust it provides is compensated for by the conveyor belt.. it pushes harder, the conveyor speeds up etc..

I bolded the part where you've gone astray. Look closer at the sentence you quoted. It does not say that the the conveyor matches the angular velocity. "...as the wheels move forward" can only be logically read as the linear velocity with respect to the surroundings/air.

well yes it doesn't say the conveyor matches angular velocity but neither does it say linear velocity of the wheels, however i think that it means angular

in full

"The plane increases it's thrust and the wheels begin to rotate. The belt compensates for the rotation of the wheels in reverse, as in the belt moves in reverse exactly as fast as the wheels move forward."

the wheels start off not rotating as in my example... then they begin to rotate then the belt compensates for the rotation and the belt moves in reverse exactly as fast as the wheels move forward

we're tallking about rotation of the wheels here hence angular not linear velocity.. it never mentions speed relative to the surrounding air

 

[JujuFish]

Originally posted by: rizzaz

Originally posted by: JujuFish

Originally posted by: rizzaz
"The belt compensates for the rotation of the wheels in reverse, as in the belt moves in reverse exactly as fast as the wheels move forward"



However the planes engines can push really hard ( harder that you could push a wheelchair!) so it can keep getting faster until it runs down the runway and takes off like normal, its no different to a normal take off except that you would need a longer runway!!

Except now we have exceeded the described senario.. the planes wheels are rotating faster than the runway.
so yes the plane could take off.. except it doesn't because all the thrust it provides is compensated for by the conveyor belt.. it pushes harder, the conveyor speeds up etc..

I bolded the part where you've gone astray. Look closer at the sentence you quoted. It does not say that the the conveyor matches the angular velocity. "...as the wheels move forward" can only be logically read as the linear velocity with respect to the surroundings/air.

well know it doesn't say the conveyor matches angular velocity or linear of the wheels however i think that it means angular

in full

"The plane increases it's thrust and the wheels begin to rotate. The belt compensates for the rotation of the wheels in reverse, as in the belt moves in reverse exactly as fast as the wheels move forward."

the wheels start off not rotating as in my example... then they begin to rotate then the belt compensates for the rotation and the belt moves in reverse exactly as fast as the wheels move forward

we're tallking about rotation of the wheels here hence angular not linear velocity.. it never mentions speed relative to the surrounding air

The key words here are "moving forward". A wheel can have all the angular velocity in the world and not be moving forward.

 

[Tom]

Hey, I just thought of something, assuming the conveyor does it's trick either direction, the wheels would probably never rotate at all, while the plane takes off..

At least if we assume there is no friction involved.

 

[rizzaz]

Originally posted by: JujuFish

Originally posted by: rizzaz

Originally posted by: JujuFish

Originally posted by: rizzaz
"The belt compensates for the rotation of the wheels in reverse, as in the belt moves in reverse exactly as fast as the wheels move forward"



However the planes engines can push really hard ( harder that you could push a wheelchair!) so it can keep getting faster until it runs down the runway and takes off like normal, its no different to a normal take off except that you would need a longer runway!!

Except now we have exceeded the described senario.. the planes wheels are rotating faster than the runway.
so yes the plane could take off.. except it doesn't because all the thrust it provides is compensated for by the conveyor belt.. it pushes harder, the conveyor speeds up etc..

I bolded the part where you've gone astray. Look closer at the sentence you quoted. It does not say that the the conveyor matches the angular velocity. "...as the wheels move forward" can only be logically read as the linear velocity with respect to the surroundings/air.

well know it doesn't say the conveyor matches angular velocity or linear of the wheels however i think that it means angular

in full

"The plane increases it's thrust and the wheels begin to rotate. The belt compensates for the rotation of the wheels in reverse, as in the belt moves in reverse exactly as fast as the wheels move forward."

the wheels start off not rotating as in my example... then they begin to rotate then the belt compensates for the rotation and the belt moves in reverse exactly as fast as the wheels move forward

we're tallking about rotation of the wheels here hence angular not linear velocity.. it never mentions speed relative to the surrounding air

The key words here are "moving forward". A wheel can have all the angular velocity in the world and not be moving forward.

i think they mean the rotation of the wheels when they say "the wheels move forward" however its impossible to say for certain so you could be correct,

in which case in your interpretation you assume that when they the say "the wheels move forward" they mean the entire plane moves forward as obviously the wheels are attached to the plane.. and planes moving forward at speed obviously can take off... I disagree with your interpretation though ! Everywhere else in the sentenace they are talking about the wheels rotating!! not literay moving through the air!

 

[1prophet]

If it's a Harrier would it take off?😉

 

[rizzaz]

Originally posted by: 1prophet
If it's a Harrier would it take off?😉

lol nice 😛

 

[JujuFish]

Originally posted by: rizzaz
i think they mean the rotation of the wheels when they say "the wheels move forward" however its impossible to say for certain so you could be correct,

in which case in your interpretation you assume that when they the say "the wheels move forward" they mean the entire plane moves forward as obviously the wheels are attached to the plane.. and planes moving forward at speed obviously can take off... I disagree with your interpretation though ! Everywhere else in the sentenace they are talking about the wheels rotating!! not literay moving through the air!

If the belt is made to match the rotation of the wheels, they would continually pick up speed. By the belt moving backwards. it creates a torque on the wheels thereby increasing the rotation of the wheels, which the conveyor must then compensate for the new increased speed which causes the rotational speed to increase as well, etc.

 

[Shame]

PSA: Planes do not fit on conveyor belts.

 

[rizzaz]

Originally posted by: JujuFish

Originally posted by: rizzaz
i think they mean the rotation of the wheels when they say "the wheels move forward" however its impossible to say for certain so you could be correct,

in which case in your interpretation you assume that when they the say "the wheels move forward" they mean the entire plane moves forward as obviously the wheels are attached to the plane.. and planes moving forward at speed obviously can take off... I disagree with your interpretation though ! Everywhere else in the sentenace they are talking about the wheels rotating!! not literay moving through the air!

If the belt is made to match the rotation of the wheels, they would continually pick up speed. By the belt moving backwards. it creates a torque on the wheels thereby increasing the rotation of the wheels, which the conveyor must then compensate for the new increased speed which causes the rotational speed to increase as well, etc.

the belt would only continualy pick up speed if the plane continualy increased thrust.

the belt moving does not directly cause the wheels to increase in rotation, consider if the plane is stationary with no thrust.. the belt moving causes the plane to move not the wheels to rotate.

as it states in the question when you apply thrust the... "wheels begin to rotate. The belt compensates for the rotation of the wheels" hence the belt is compensating for the thrust which is causing the wheels to rotate..

if you increase the thrust the belts speed will increase, if you don't it wont.....

 

[JujuFish]

Originally posted by: rizzaz
the belt would only continualy pick up speed if the plane continualy increased thrust.

the belt moving does not directly cause the wheels to increase in rotation, consider if the plane is stationary with no thrust.. the belt moving causes the plane to move not the wheels to rotate.

as it states in the question when you apply thrust the... "wheels begin to rotate. The belt compensates for the rotation of the wheels" hence the belt is compensating for the thrust which is causing the wheels to rotate..

if you increase the thrust the belts speed will increase, if you don't it wont.....

Do you know what torque is?

 

[rizzaz]

Originally posted by: JujuFish

Originally posted by: rizzaz
the belt would only continualy pick up speed if the plane continualy increased thrust.

the belt moving does not directly cause the wheels to increase in rotation, consider if the plane is stationary with no thrust.. the belt moving causes the plane to move not the wheels to rotate.

as it states in the question when you apply thrust the... "wheels begin to rotate. The belt compensates for the rotation of the wheels" hence the belt is compensating for the thrust which is causing the wheels to rotate..

if you increase the thrust the belts speed will increase, if you don't it wont.....

Do you know what torque is?

yup torque is force at a distance from a point of axis...

and yes the the belt transfers torque to the wheels i didn't say otherwise...,

however you were surgesting a feedback loop whereby the belt increasing in speed directly causes the wheels to increase in rotation which casuses the belt to increase etc, thats just silly


there are other factors such as rolling resistance which oppose the increase in speed of the wheels, only the planes thrust compensating for rolling resistance prevents the wheels from slowing

or to put it another way the plane increases thrust which makes the plane move forward which causes the wheels to rotate faster so the belt speeds up which transfers greater force through the wheels which through resistance casuses an equal opposing force to the thrust of the plane which stops moving forward...

I think your assuming the wheels always rotate at the same speed as the belt ?

 

[CallMeJoe]

30 pages, 585 posts and I can't believe people are still debating this nonsense.
Any "pilots" who say he plane won't fly, turn in your license to the nearest FSDO and go back to ground school.
Any "engineers" who agree, burn your degree and go back to freshman physics.
An aircraft doesn't care what the ground does so long as it stays beneath the gear.
Aircraft fly by reacting with the AIR.

 

[Kelemvor]

OK. Some people obviously aren't grasping the concept so I'll try to make it real simple.

Most physics problems assume that there is no friction between moving parts so let's assume that there is no friction between the airplane's wheel and the axle/hub that it spins on. THe ball bearings or whatever are perfectly designed and all friction is gone.

Bassed on this fact, the spinning of the wheels has nothing to do with causing the airplane to move or not. Let's say the airplane has it's engines turned off. The treadmill can run as fast as it wants and this will cause the wheels to spin at the same rate, but the airplane will not move.

Now let's say the treadmill is off. If the plane turns its engines on, the thrust pushing the air through the engines and out the back will cause the plane to move. THe only reason the wheels move is because they are touching the ground. THey have nothing to do with actually propelling the airplane.

SO now if we combine those two, when the plane moves forward and the treadmill spins the opposite direction, the wheels will spin very fast, but they put forth no force on the airplane because of the frictionless hubs the wheels spin on. The airplane will move forward because it uses the AIR to move and not the ground.

Now if this question were worded that a carr with wings was on the same treadmill, then it would not take off because the car gets its movement by pushing itself along on the ground. SO if the treadmill spins the other way, it is jsut like riding a bike on a treadmill, you don't actually move.

But since a plane doesn't get it's pwoer from wheels pushing it, the treadmill can spin at 10,000 mph and the wheels will spin at the same rate, but that has no affect on the plane.

Does that sum it up well enough? Is anyone still confused about this?

 

[Thegonagle]

Jeez, why is this 500+ posts long? Are there that many people who don't know how an airplane actually works?

(For the record, of course it takes off.)

 

[aigomorla]

Originally posted by: CallMeJoe
30 pages, 585 posts and I can't believe people are still debating this nonsense.
Any "pilots" who say he plane won't fly, turn in your license to the nearest FSDO and go back to ground school.
Any "engineers" who agree, burn your degree and go back to freshman physics.
An aircraft doesn't care what the ground does so long as it stays beneath the gear.
Aircraft fly by reacting with the AIR.

and u obviously need the reread the question carefuly. It states a condition of no air is being passed though the wings of the plane. The engines are located in the back meaning its a direct push. obviously the intake for the air will be located in the front. without wind passing though the wings:

No wind passing thought the wings = no lift. END of DISCUSSION

Also i forgot to mention, the guy on the top who is refering to torque. the question also stated that the tires had excellent traction which means the value for (mu)K is equal to the force exerted. That means the wheels will hold the ground and accelertate as the treadmill. So the plane will just hold its place and not lift.

 

[JujuFish]

Originally posted by: aigomorla
and u obviously need the reread the question carefuly. It states a condition of no air is being passed though the wings of the plane.

No wind passing thought the wings = no lift. END of DISCUSSION

Oh the irony.

 

[Thegonagle]

Originally posted by: aigomorla

Originally posted by: CallMeJoe
30 pages, 585 posts and I can't believe people are still debating this nonsense.
Any "pilots" who say he plane won't fly, turn in your license to the nearest FSDO and go back to ground school.
Any "engineers" who agree, burn your degree and go back to freshman physics.
An aircraft doesn't care what the ground does so long as it stays beneath the gear.
Aircraft fly by reacting with the AIR.

and u obviously need the reread the question carefuly. It states a condition of no air is being passed though the wings of the plane.

No wind passing thought the wings = no lift. END of DISCUSSION

How does a treadmill on the ground prevent air from passing over/under the wings?

 

[PurdueRy]

Originally posted by: aigomorla

Originally posted by: CallMeJoe
30 pages, 585 posts and I can't believe people are still debating this nonsense.
Any "pilots" who say he plane won't fly, turn in your license to the nearest FSDO and go back to ground school.
Any "engineers" who agree, burn your degree and go back to freshman physics.
An aircraft doesn't care what the ground does so long as it stays beneath the gear.
Aircraft fly by reacting with the AIR.

and u obviously need the reread the question carefuly. It states a condition of no air is being passed though the wings of the plane. The engines are located in the back meaning its a direct push. obviously the intake for the air will be located in the front. without wind passing though the wings:

No wind passing thought the wings = no lift. END of DISCUSSION

Also i forgot to mention, the guy on the top who is refering to torque. the question also stated that the tires had excellent traction which means the value for (mu)K is equal to the force exerted. That means the wheels will hold the ground and accelertate as the treadmill. So the plane will just hold its place and not lift.

1. It says the engines are not pushing air over the wings since they are behind them...it does not say it is not pushing the airplane through the air.

2. You need to draw a FBD

 

[CallMeJoe]

Originally posted by: aigomorla
and u obviously need the reread the question carefuly. It states a condition of no air is being passed though the wings of the plane.
No wind passing thought the wings = no lift. END of DISCUSSION

"The plane increases it's thrust and the wheels begin to rotate. The belt compensates for the rotation of the wheels in reverse, as in the belt moves in reverse exactly as fast as the wheels move forward.
And if it matters, it's a nice sunny day and you have good tires, so you get perfect traction on the belt at all times. Your plane also happens to be very powerful and you can give it as much thrust as you like, but the source of thrust is at the back of the plane so it never provides airflow over the wing.
Does the plane take off? "

The source of thrust doesn't force air over the wing. So what?
The wheels do not start to turn until the aircraft starts to move forward.
If the aircraft moves forward,AIR FLOWS OVER THE WINGS

 

[JujuFish]

Originally posted by: rizzaz
yup torque is force at a distance from a point of axis...

Okay, good.

If the ground was stationary, the wheels are spinning.

In our scenario, the ground also moves, and in opposite direction. This increases the torque on the wheels causing them to spin faster. The conveyor belt will continually be trying to "catch up" so to speak with the speed of the wheels. However, in doing so, it would be increasing the rotation of the wheels along the way. The result is they both continually increase.

 

[archiloco]

Originally posted by: CallMeJoe

Originally posted by: aigomorla
and u obviously need the reread the question carefuly. It states a condition of no air is being passed though the wings of the plane.
No wind passing thought the wings = no lift. END of DISCUSSION

"The plane increases it's thrust and the wheels begin to rotate. The belt compensates for the rotation of the wheels in reverse, as in the belt moves in reverse exactly as fast as the wheels move forward.
And if it matters, it's a nice sunny day and you have good tires, so you get perfect traction on the belt at all times. Your plane also happens to be very powerful and you can give it as much thrust as you like, but the source of thrust is at the back of the plane so it never provides airflow over the wing.
Does the plane take off? "

The source of thrust doesn't force air over the wing. So what?
The wheels do not start to turn until the aircraft starts to move forward.
If the aircraft moves forward,AIR FLOWS OVER THE WINGS

even if it did move forward for 1 inch or heck even 30 ft and the belt stops the plane and it keeps on going at 20mph forever it will still not create enough lift.

 

[PurdueRy]

Originally posted by: archiloco

Originally posted by: CallMeJoe

Originally posted by: aigomorla
and u obviously need the reread the question carefuly. It states a condition of no air is being passed though the wings of the plane.
No wind passing thought the wings = no lift. END of DISCUSSION

"The plane increases it's thrust and the wheels begin to rotate. The belt compensates for the rotation of the wheels in reverse, as in the belt moves in reverse exactly as fast as the wheels move forward.
And if it matters, it's a nice sunny day and you have good tires, so you get perfect traction on the belt at all times. Your plane also happens to be very powerful and you can give it as much thrust as you like, but the source of thrust is at the back of the plane so it never provides airflow over the wing.
Does the plane take off? "

The source of thrust doesn't force air over the wing. So what?
The wheels do not start to turn until the aircraft starts to move forward.
If the aircraft moves forward,AIR FLOWS OVER THE WINGS

even if it did move forward for 1 inch or heck even 30 ft and the belt stops the plane and it keeps on going at 20mph forever it will still not create enough lift.

How does the belt stop the plane....Draw me a FBD showing the connection

 

[Throwmeabone]

Originally posted by: FrankyJunior
OK. Some people obviously aren't grasping the concept so I'll try to make it real simple.

Most physics problems assume that there is no friction between moving parts so let's assume that there is no friction between the airplane's wheel and the axle/hub that it spins on. THe ball bearings or whatever are perfectly designed and all friction is gone.

Bassed on this fact, the spinning of the wheels has nothing to do with causing the airplane to move or not. Let's say the airplane has it's engines turned off. The treadmill can run as fast as it wants and this will cause the wheels to spin at the same rate, but the airplane will not move.

Now let's say the treadmill is off. If the plane turns its engines on, the thrust pushing the air through the engines and out the back will cause the plane to move. THe only reason the wheels move is because they are touching the ground. THey have nothing to do with actually propelling the airplane.

SO now if we combine those two, when the plane moves forward and the treadmill spins the opposite direction, the wheels will spin very fast, but they put forth no force on the airplane because of the frictionless hubs the wheels spin on. The airplane will move forward because it uses the AIR to move and not the ground.

Now if this question were worded that a carr with wings was on the same treadmill, then it would not take off because the car gets its movement by pushing itself along on the ground. SO if the treadmill spins the other way, it is jsut like riding a bike on a treadmill, you don't actually move.

But since a plane doesn't get it's pwoer from wheels pushing it, the treadmill can spin at 10,000 mph and the wheels will spin at the same rate, but that has no affect on the plane.

Does that sum it up well enough? Is anyone still confused about this?

bravo that is the best explanation so far

 

[CallMeJoe]

Originally posted by: PurdueRy
How does the belt stop the plane....Draw me a FBD showing the connection

The belt stops the plane as it accelerates to infinite speed countering the forward thrust of the aircraft, grinding the wheels and landing gear away to nothing. It's the only way you keep the plane from flying.

 

[PurdueRy]

Originally posted by: CallMeJoe

Originally posted by: PurdueRy
How does the belt stop the plane....Draw me a FBD showing the connection

The belt stops the plane as it accelerates to infinite speed countering the forward thrust of the aircraft, grinding the wheels and landing gear away to nothing. It's the only way you keep the plane from flying.

LOL 😛

don't confuse him!