Originally posted by: dainthomas
Originally posted by: Eeezee
So many people on this forum don't know what a hypothetical situation is. Obviously no treadmill exists that is capable of infinite acceleration. However, if it did, and the plane were placed on top of it, and the treadmill provided enough force to counteract any acceleration provided by the engine, then the plane would not take off.
If you have a magical infinite treadmill and normal wheels it will melt the wheel bearings, rip the wheels off, and the plane will crash.
If you have a magical infinite treadmill and magical frictionless wheels, then no force is generated on the fuselage and the plane takes off.
If you have a normal treadmill and normal wheels, the plane takes off.
I honestly can't believe this is still being debated.
:laugh:Originally posted by: The Boston Dangler
http://dsc.discovery.com/video...956&titleId=1347908538
Originally posted by: Jeff7
:laugh:Originally posted by: The Boston Dangler
http://dsc.discovery.com/video...956&titleId=1347908538
"We're letting the Intertubes down."
Originally posted by: jagec
Originally posted by: her209
The maximum amount of frictional force that can be applied by the treadmill to the wheel is precisely, the normal force N multiplied by the coefficient of static friction, us. Any more force and the wheels slip, in which case the amount of frictional force decreases because uk is always less than us. Conversely, if the airplane applies more force than N * us, the plane overcomes the friction between the wheels and treadmill.Originally posted by: Eeezee
Precisely; in other words, the treadmill provides sufficient friction to counteract ANY movement. That's the hypothetical situation.
To find a:
Ff = N * us = mplane * a
Rewritten and reduced, it comes to:
a = g * us
Easily, any jet engine can generate enough force on a plane such that its acceleration > a, especially a hypothetical one.
I did the calculation earlier on. Assuming a 100,000 kg plane (somewhat lighter than a 777), the maximum force that can be generated on the wheels before exceeding their traction is 880kN. The engine packages for the 777 vary from 640 to 1050kN. So you can't say that any jet engine can generate enough force to break the wheels loose.
Originally posted by: dug777
Originally posted by: Tweak155
Originally posted by: Eeezee
Originally posted by: Tweak155
Dude, they don't even understand with simple words. Formulas will just make them have to use bikes instead of skateboards to prove their point.
You're a moron. You need to get over yourself. I'm sure you've never made a mistake in your pathetic little existence.
I (and I'm sure most of ATOT) hope you DIAF
Wow at least I didn't try to voice my opinion as "most of ATOT"... who is full of them self when they try to speak on the behalf of everyone? And I certainly don't claim authority over anyone's intelligence level.
And I never directly called anyone a moron, I was poking fun at a previous post.
It was a joke. And wasn't even aimed at you. Reminds me about a song about being vain.
That being said, I hope you don't take any of this seriously.
You're a complete jerk, Tweak155.
Your grasp of practical physics is weak. Being towed is analogous to a treadmill. The ground moves under you the same way a treadmill would. The 'car' would be the same as the engines/prop on a plane. You need to try it as you are getting it wrong.Originally posted by: spidey07
Originally posted by: ultimatebob
Originally posted by: spidey07
Originally posted by: Tweak155
Provided a realistic airplane that isn't underpowered and a treadmill / conveyor belt that man can make, anyone with common sense should agree the airplane will take off.
I won't ever disagree that you COULD CREATED a scenario where it wouldn't, but any logical person would agree it isn't realistic.
Again,
Stay in bounds of the original question.
I honestly think this type of question is what separates smart people from others. All kinds of assumptions are made by plane take off folks. The truly smart people, that have a really good grasp of the physics involved can see and mentally and mathematically deduce the problem.
Then again me and my buddies used to ride on a skateboard on a treadmill at max speed and first hand experienced just how much the treadmill can push you back. Real world + experience + advanced physics = plane doesn't take off.
Exactly. I still say that the Mythbusters are going to end up crashing the plane!
Do you know just how hard it is to pull off a kickflip on a treadmill?
Such a simple trick that you can do without thought while rolling. Try it on a treadmill. It's hard. really hard.
To deny the treadmill doesn't push the plane back - I just can't see how people can even believe this. Come up with all kinds of analogies you wish. You can't deny physics.
I know it seems like trolling but we really did spend countless hundreds of hours on a skateboard on a treadmill. What the heck were we gonna do? It was raining.
As the treadmill sped up you had to pull yourself harder and harder just to maintain position.
Originally posted by: spidey07
And you are still breaking the original constraints of the question. I don't see why this is so hard for people to get.
Any advancement by the plane will be met with acceleration of the treadmill preventing the plane from moving. The force of the engines if finite. By very definition of the problem the treadmills force (acceleration) isn't.
Originally posted by: smack Down
Originally posted by: her209
The maximum amount of frictional force that can be applied by the treadmill to the wheel is precisely, the normal force N multiplied by the coefficient of static friction, us. Any more force and the wheels slip, in which case the amount of frictional force decreases because uk is always less than us. Conversely, if the airplane applies more force than N * us, the plane overcomes the friction between the wheels and treadmill.Originally posted by: Eeezee
Precisely; in other words, the treadmill provides sufficient friction to counteract ANY movement. That's the hypothetical situation.
To find a:
Ff = N * us = mplane * a
Rewritten and reduced, it comes to:
a = g * us
Easily, any jet engine can generate enough force on a plane such that its acceleration > a, especially a hypothetical one.
Sure but can it generate more then a of a hypothetical treadmill? Do you know what the surface of the treadmill is?
Originally posted by: spidey07
And you are still breaking the original constraints of the question. I don't see why this is so hard for people to get.
Any advancement by the plane will be met with acceleration of the treadmill preventing the plane from moving. The force of the engines if finite. By very definition of the problem the treadmills force (acceleration) isn't.
It is a free body. The treadmill only can effect the rotational value of the wheels, nothing more. It CANNOT effect the movement of the free body, only the rotational speed of the wheels. The only force it then applies is to the plane is from friction in the bearings, which is not significant. You do not understand free bodies and how the wheel's rotation creates the plane as a free body. The only way for the treadmill to cancel the plane's forward motion (acceleration) where F on plane by the treadmill is F plane engine generates. For the treadmill to generate the same force on the plane as the engines create on the plane, the treadmill MUST have a delta V much higher than the speed of the airplane. So, the treadmill must move (pulling it out of the air) 400mph while the plane is only moving 50 mph. Voids the equation to match what you are implying.Originally posted by: spidey07
And you are still breaking the original constraints of the question. I don't see why this is so hard for people to get.
Any advancement by the plane will be met with acceleration of the treadmill preventing the plane from moving. The force of the engines if finite. By very definition of the problem the treadmills force (acceleration) isn't.
Originally posted by: Throckmorton
Originally posted by: jagec
I did the calculation earlier on. Assuming a 100,000 kg plane (somewhat lighter than a 777), the maximum force that can be generated on the wheels before exceeding their traction is 880kN. The engine packages for the 777 vary from 640 to 1050kN. So you can't say that any jet engine can generate enough force to break the wheels loose.
Wheels spin!
Originally posted by: spidey07
And you are still breaking the original constraints of the question. I don't see why this is so hard for people to get.
Any advancement by the plane will be met with acceleration of the treadmill preventing the plane from moving. The force of the engines if finite. By very definition of the problem the treadmills force (acceleration) isn't.
Originally posted by: Kev
Originally posted by: spidey07
And you are still breaking the original constraints of the question. I don't see why this is so hard for people to get.
Any advancement by the plane will be met with acceleration of the treadmill preventing the plane from moving. The force of the engines if finite. By very definition of the problem the treadmills force (acceleration) isn't.
Going by laws of physics of the universe we currently live in, the italicized statement above is *physically impossible*
Come back once you comprehend that, mkay?
Summary is that there was a screwup somewhere, and yes, they have filmed the stuff for Plane on a Treadmill, and it didn't fit in the Airplane Hour episode, so it's got its own episode now.Originally posted by: Anubis
Originally posted by: Jeff7
:laugh:Originally posted by: The Boston Dangler
http://dsc.discovery.com/video...956&titleId=1347908538
"We're not letting the Intertubes down."
i dont have sound at work whats he saying
Originally posted by: spidey07
Originally posted by: Kev
Originally posted by: spidey07
And you are still breaking the original constraints of the question. I don't see why this is so hard for people to get.
Any advancement by the plane will be met with acceleration of the treadmill preventing the plane from moving. The force of the engines if finite. By very definition of the problem the treadmills force (acceleration) isn't.
Going by laws of physics of the universe we currently live in, the italicized statement above is *physically impossible*
Come back once you comprehend that, mkay?
I understand it fully. Hence the paradox.
Come back when you stay within bounds of the problem. As soon as the plane advances a single micron, that wheels are moving forward faster than the treadmill, which according to the problem can't happen. That's where the infinite acceleration comes in.
Originally posted by: astroidea
The plane takes of depending on which plane it is!
So the main argument that the plane would still take off is that there's no counter force keeping the plane from moving forward as the thrust of the plane is independent from the wheels. So as long as the wheels roll freely, the plane will still take off.
However, there is a counter force! Rotational friction. There is a frictional force in the bearings of the wheels. It does not roll completely freely without any opposing forces. The thrust force the plane puts out would be needed to counteract this frictional force.
Therefore, the quicker the wheels spin, the more force the plane would have to put out to spin the wheels.
But isn't the conveyer belt pushing the same amount of force on the wheels in the opposite direction?
So when would the plane actually move forward relative to the air?
Well first, let's imagine this situation:
The plane is on a conveyer belt that's moving backwards at 100mph. The plane is moving forwards at 100mph also. So right now, the plane isn't moving relative to the air right? But what would happen if the plane suddenly stopped all its engines? The coveyer belt would begin to move the plane backwards. It would no longer be able to maintain the static air speed.
Therefore, we can reasonably deduce that it does indeed take some force from the plane's thrust in order to counteract the motion of the conveyer belt.
So how much force would it take to keep the plane stationary with the air when the belt is moving backwards at 1000000000000 miles per hour? Would the plane have enough power to keep it stationary? Probably not.
But then again, is it even possible for the tires to still be in contact with the treadmill at 100000000000 miles per hour? According to newtonian physics, once the frictional force of the bearings exceed the frictional force between the tires and the surface of the conveyer belt, wouldn't the tires lose grip with the surface? Once the tires lose surface, the plane will only have to generate enough thrust to counteract the frictional force between the tires and the surface of the belt in order to move forward.
So therefore, the plane will move forward, but only when the plane is able to generate enough thrust for the friction of the tires to break free from the belt.
But is there any plane that has a powerful enough engine that can generate enough force to break free?
Let's look at the Boeing 777.
According to wikipedia, it generates 418,000N of thrust, and has a mass of 139,225kg.
The coefficient of static friction between tires and tarmac is about 0.7.
If you work out the math, µmg is (0.7)(139225)(9.8) = 956,058N.
This is over twice as much force as what the 418,000N of thrust the engines put out.
And if you consider the hundreds of opposing forces that I haven't accounted for, it's even less likely to be able to break free from the friction.
Thus, Plane DOESN'T TAKE OFF
But what if you had a plane with a better weight to thrust ratio?
Well, I let's look at the F22 Raptor.
According to wikipedia, the two turbofan engines generates a total of 311,000N of thrust. The plane when empty has a mass of 14,365kg.
So given that, let's work out the math again. (0.7)(14365)(9.8) = 98,544N
In this case, the 311,000N of thrust is significantly greater than 98,544N of frictional force. So in this case, the plane would take off!
In conclusion: THE PLANE MAY OR MAY NOT TAKE OFF DEPENDING ON WHICH PLANE IT IS!
Originally posted by: astroidea
The plane takes of depending on which plane it is!
So the main argument that the plane would still take off is that there's no counter force keeping the plane from moving forward as the thrust of the plane is independent from the wheels. So as long as the wheels roll freely, the plane will still take off.
However, there is a counter force! Rotational friction. There is a frictional force in the bearings of the wheels. It does not roll completely freely without any opposing forces. The thrust force the plane puts out would be needed to counteract this frictional force.
Therefore, the quicker the wheels spin, the more force the plane would have to put out to spin the wheels.
But isn't the conveyer belt pushing the same amount of force on the wheels in the opposite direction?
So when would the plane actually move forward relative to the air?
Well first, let's imagine this situation:
The plane is on a conveyer belt that's moving backwards at 100mph. The plane is moving forwards at 100mph also. So right now, the plane isn't moving relative to the air right? But what would happen if the plane suddenly stopped all its engines? The coveyer belt would begin to move the plane backwards. It would no longer be able to maintain the static air speed.
Therefore, we can reasonably deduce that it does indeed take some force from the plane's thrust in order to counteract the motion of the conveyer belt.
So how much force would it take to keep the plane stationary with the air when the belt is moving backwards at 1000000000000 miles per hour? Would the plane have enough power to keep it stationary? Probably not.
But then again, is it even possible for the tires to still be in contact with the treadmill at 100000000000 miles per hour? According to newtonian physics, once the frictional force of the bearings exceed the frictional force between the tires and the surface of the conveyer belt, wouldn't the tires lose grip with the surface? Once the tires lose surface, the plane will only have to generate enough thrust to counteract the frictional force between the tires and the surface of the belt in order to move forward.
So therefore, the plane will move forward, but only when the plane is able to generate enough thrust for the friction of the tires to break free from the belt.
But is there any plane that has a powerful enough engine that can generate enough force to break free?
Let's look at the Boeing 777.
According to wikipedia, it generates 418,000N of thrust, and has a mass of 139,225kg.
The coefficient of static friction between tires and tarmac is about 0.7.
If you work out the math, µmg is (0.7)(139225)(9.8) = 956,058N.
This is over twice as much force as what the 418,000N of thrust the engines put out.
And if you consider the hundreds of opposing forces that I haven't accounted for, it's even less likely to be able to break free from the friction.
Thus, Plane DOESN'T TAKE OFF
But what if you had a plane with a better weight to thrust ratio?
Well, I let's look at the F22 Raptor.
According to wikipedia, the two turbofan engines generates a total of 311,000N of thrust. The plane when empty has a mass of 14,365kg.
So given that, let's work out the math again. (0.7)(14365)(9.8) = 98,544N
In this case, the 311,000N of thrust is significantly greater than 98,544N of frictional force. So in this case, the plane would take off!
In conclusion: THE PLANE MAY OR MAY NOT TAKE OFF DEPENDING ON WHICH PLANE IT IS!
Originally posted by: her209
Originally posted by: smack Down
Originally posted by: her209
The maximum amount of frictional force that can be applied by the treadmill to the wheel is precisely, the normal force N multiplied by the coefficient of static friction, us. Any more force and the wheels slip, in which case the amount of frictional force decreases because uk is always less than us. Conversely, if the airplane applies more force than N * us, the plane overcomes the friction between the wheels and treadmill.Originally posted by: Eeezee
Precisely; in other words, the treadmill provides sufficient friction to counteract ANY movement. That's the hypothetical situation.
To find a:
Ff = N * us = mplane * a
Rewritten and reduced, it comes to:
a = g * us
Easily, any jet engine can generate enough force on a plane such that its acceleration > a, especially a hypothetical one.
Sure but can it generate more then a of a hypothetical treadmill? Do you know what the surface of the treadmill is?
You've obviously missed the point. The treadmill can exert only so much force on the wheels via friction before the tires slip. It doesn't matter if the treadmill can accelerate from 0 to 1,000,000 mph in 5 seconds.
Originally posted by: smack Down
Originally posted by: her209
Originally posted by: smack Down
Originally posted by: her209
The maximum amount of frictional force that can be applied by the treadmill to the wheel is precisely, the normal force N multiplied by the coefficient of static friction, us. Any more force and the wheels slip, in which case the amount of frictional force decreases because uk is always less than us. Conversely, if the airplane applies more force than N * us, the plane overcomes the friction between the wheels and treadmill.Originally posted by: Eeezee
Precisely; in other words, the treadmill provides sufficient friction to counteract ANY movement. That's the hypothetical situation.
To find a:
Ff = N * us = mplane * a
Rewritten and reduced, it comes to:
a = g * us
Easily, any jet engine can generate enough force on a plane such that its acceleration > a, especially a hypothetical one.
Sure but can it generate more then a of a hypothetical treadmill? Do you know what the surface of the treadmill is?
You've obviously missed the point. The treadmill can exert only so much force on the wheels via friction before the tires slip. It doesn't matter if the treadmill can accelerate from 0 to 1,000,000 mph in 5 seconds.
You've obviously missed the point the force is limited based on the surface of the treadmill the question doesn't define what its coefficient of friction is so the only reasonable assumption is infinite.