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Airplane on a treadmill


scn64

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ok, i think people are arguing different points and that's why no one agrees with anyone else.

 

 

 

forget about wheels, forget about thrust, forget about everything. there are 2 cases to consider here.

 

 

 

1. IF the plane is stationary with respect to the ground(treadmill, whatever). It WILL NOT take off. there will be no air moving over the wings, and therefore will not recieve the necessary lift to take off.

 

 

 

2. IF, however, the plane begins to move(i.e. the thrust becomes greater than the frictional force between the wheels and the treadmill) with respect to the ground(treadmill), then the plane MAY take off, assuming it reaches the required speed to induce take-off conditions(lift force becomes greater than the weight of the plane).

 

 

 

the fact that you stated in your original post that the plane was moving at the same speed as the treadmill lead me to believe that you meant the first case here. in which case, the answer to your question would be no, the plane does not take off.

 

 

 

i hope this clears the problems up for people who are still confused.

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ok, i think people are arguing different points and that's why no one agrees with anyone else.

 

 

 

forget about wheels, forget about thrust, forget about everything. there are 2 cases to consider here.

 

 

 

1. IF the plane is stationary with respect to the ground(treadmill, whatever). It WILL NOT take off. there will be no air moving over the wings, and therefore will not recieve the necessary lift to take off.

 

 

 

2. IF, however, the plane begins to move(i.e. the thrust becomes greater than the frictional force between the wheels and the treadmill) with respect to the ground(treadmill), then the plane MAY take off, assuming it reaches the required speed to induce take-off conditions(lift force becomes greater than the weight of the plane).

 

 

 

the fact that you stated in your original post that the plane was moving at the same speed as the treadmill lead me to believe that you meant the first case here. in which case, the answer to your question would be no, the plane does not take off.

 

 

 

i hope this clears the problems up for people who are still confused.

 

Pretty much what I said in my last post. Same two scenarios. The whole problem really isn't that complicated.

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You both are assuming that the plane stays in the same spot, which is doesnt. The plane moves forward.

 

No. Assuming you're talking to ktmcf121 and I, we have made assumptions arguing for both scenarios. We have also given the result to both scenarios.

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it would fly(considering the wheel axles are very strong and heat resistant, if they arent, the wheel's would melt, and then the plane would be ground down until the thrusters stop working, and then the inertia of the treadmill would send the plane backwards very fast, and it would go into orbit so...it flies anyways! \' )

 

 

 

i think my logic is correct...

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No lift means no takeoff, unless you have a VERY powerful airplane such as a fighter that has a big enough thrust to weight ratio to takeoff without needing lift.

 

 

 

Thank you for that very informative post!

He's got a point. Harriers have enough thrust to take off with no air flow over the wing.

 

 

 

 

 

But a 747 or something defeinately not. Needs the horizontal movement to create the conditions it needs to achieve lift.

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This is a great question and its a real brain-teaser. I think I have the next brain-teaser.

 

 

 

Who the hell would try to fly a plane off a giant treadmill?

I shall take my flock underneath my own wing, and kick them right the [bleep] out of the tree. If they were meant to fly, they won't break their necks on the concrete.
So, what is 1.111... equal to?

10/9.

 

Please don't continue.

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it wont matter. the airplane still has 2 use its engines to take off, so the treadmill would have to move freeley, or still have 2 use an engine to move. the planes engines need wind to go through them so it is easier to move them, pointehem down to take off.

 

 

 

any way, the power needed to run the treadmill would take up too much power, so it would be better 4 us to just keep with the plane.

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it wont matter. the airplane still has 2 use its engines to take off, so the treadmill would have to move freeley, or still have 2 use an engine to move. the planes engines need wind to go through them so it is easier to move them, pointehem down to take off.

 

 

 

any way, the power needed to run the treadmill would take up too much power, so it would be better 4 us to just keep with the plane.

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You both are assuming that the plane stays in the same spot, which is doesnt. The plane moves forward.

 

 

 

in that case, the first post needs to be edited, because it made it seem as if the plane stays stationary with respect to the treadmill.

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:? You guys are thinking too linear.

 

 

 

There are so many possibilities because of there being not much info in the first post.

 

 

 

First of all, is this on earth? If it is, we can assume gravity to be as it is. If not, gravity can be anything else. If there was no gravity, there would be no normal force, therefore meaning the two are not in contact, and this is not a problem

 

 

 

but since it is, we can say that it is on a planet that has some gravity. Now the next problem concerning gravity is, how much weight can the treadmill resist before it crunches. Therefore we wonder, is the structural stability of the treadmill good enough?

 

 

 

I guess we are assuming it is. Now to go along with forces, another question comes up. what is the force of friction on the plane wheels? Is there no friction? If so, the two devices have independent thrusts (Plane goes one way, the treadmill goes the other).

 

 

 

Another problem with the initial question. It says the Two objects have matching but opposite speeds. Thats all fine and dandy, but the equation for force is equal to mass times acceleration. Unless both the mass are the same, they will not be exerting equal and opposite forces on each other (again if there is friction)Also, Speed is not the same as acceleration, so even if they have equal speeds, acceleration might not be equal.

 

 

 

Also, wind speeds and the direction would also play a huge part.

 

 

 

This is not a very good question.

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The Set Up:

 

 

 

LetÃÆââââ¬Å¡Ã¬Ã¢ââ¬Å¾Ã¢s say that we have a jet airplane (like a 747 for example) trying to take off on a giant runway sized treadmill. The treadmill, which turns in the opposite direction that the plane is facing, is capable of precisely matching the speed of the airplane.

 

 

 

Well, what if you have a plane like a Hornet which can takeoff/land vertically? Or a turboprop with engines that force air over the wings?

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Wouldn't there be to much friction from the wheels turning one way and the treadmill going the other way?
Assuming there is the gravity if earth it is hard to say. There is a force pushing the plane one way, and one under pulling the plane another, the thing is, i still cant imagine what would happen at the wheels. If the wheels move with the plane, it might be possible to take off, but im still not sure. if the wheels dont move then it just gets pulled along with the treadmill. If the wheels spin in the direction the treadmill is going... im not sure what happens.

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Wouldn't there be to much friction from the wheels turning one way and the treadmill going the other way?
Assuming there is the gravity if earth it is hard to say. There is a force pushing the plane one way, and one under pulling the plane another, the thing is, i still cant imagine what would happen at the wheels. If the wheels move with the plane, it might be possible to take off, but im still not sure. if the wheels dont move then it just gets pulled along with the treadmill. If the wheels spin in the direction the treadmill is going... im not sure what happens.

 

 

 

the wheels on an airplane spin freely, much like the "hot-wheels car" example. and your hand on the hotwheels car would be the "thrust" on a plane. imagine putting a hotwheels car on an actual treadmill, or just go do it if you have both of those items. the point is that the wheels are not connected to or driven by the engine of the plane, therefore the wheels will always be moving at the same "speed" as the treadmill, independent of the plane. the only force that gets transferred to the plane from the treadmill would simply be friction, and that force would be very small due to the small contact patch of the wheels and the low rolling resistance of the bearings in the wheels.

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The Set Up:

 

 

 

LetÃÆââââ¬Å¡Ã¬Ã¢ââ¬Å¾Ã¢s say that we have a jet airplane (like a 747 for example) trying to take off on a giant runway sized treadmill. The treadmill, which turns in the opposite direction that the plane is facing, is capable of precisely matching the speed of the airplane.

 

 

 

Well, what if you have a plane like a Hornet which can takeoff/land vertically? Or a turboprop with engines that force air over the wings?

 

Then you have a completely different problem, now don't you?

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*snip*

 

 

 

That wasn't a very good post, you're looking into it too practically and being nitpicky.

 

 

 

The question was good enough to spark the discussion and debates that it has done.

La lune ne garde aucune rancune.

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*snip*

 

 

 

That wasn't a very good post, you're looking into it too practically and being nitpicky.

 

 

 

The question was good enough to spark the discussion and debates that it has done.

 

Yes thats good and all. The problem though, is that scientifically, it was terrible. There is no way to prove either side without looking at it specifically. Ergo, a stalemate.

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*snip*

 

 

 

That wasn't a very good post, you're looking into it too practically and being nitpicky.

 

 

 

The question was good enough to spark the discussion and debates that it has done.

 

Yes thats good and all. The problem though, is that scientifically, it was terrible. There is no way to prove either side without looking at it specifically. Ergo, a stalemate.

 

I have to agree. The questions leaves too many different scenarios. I doesn't specifically give one piece of information so you're forced to look at it from both points of view and make assumptions based on both sides.

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I like the toy car idea.

 

 

 

For an experiment... If anyone wants to try it.

 

 

 

Take a toy car, something that the wheels move freely and put it on a moving belt, like a treadmill.

 

 

 

Have some sort of external force, your hand would be ideal for this... To keep the car from moving when the treadmill is turned on.

 

 

 

If I'm right, that should simulate no friction and no mass? Or simply the car going at the same "speed" as the treadmill. Bear with me... It's hurting my head too.

 

 

 

Turn on the treadmill and watch the wheels start to move.

 

 

 

Apply a small amount of force on the car, easily done with your hand. But it'd be better if you could add measurable force. The car should start moving forward. The reason you'd want measurable force is to eliminate you adding any extra force when you sense the speed of the treadmill increase.

 

 

 

While you're doing this, get someone to turn up the speed of the treadmill.

 

 

 

If the car continues to move forward then it can obviously create lift (if it had wings) if the car starts to move backwards or stays still, no lift can be created until you increase the force that is being exerted on the car.

 

 

 

 

 

 

 

Now that I think about it, how is the treadmill moving? The plane sits stationary until the jet engines (external force) act and propel the plane forward. So that'd mean that the treadmill is off. The plane will start moving forward due to thrust.

 

 

 

The treadmill will then measure the ground speed of the plane (Speed = Distance traveled divided by time?) and start moving in the opposite direction.

 

 

 

To be easy on you all, say on a runway the planes wheels start moving at 10 rotations per minute. If they were on an opposite moving treadmill which is also pushing the wheels in the same direction using the ground speed of the plane, this would make the wheels turn at 20 rotations per minute. So to be quite honest, in your way of thinking technically the plane should be moving forward even faster.

 

 

 

I think what everyone is trying to say when they think that the speed of the treadmill is making the plane stand still is that the treadmill is an equal force in the opposite direction, which I'm afraid it isn't.

 

 

 

You know... I think I started rambling there.

 

 

 

Here's a pretty picture to help. ^_^

 

 

 

planeontreadmillqd6.gif

 

 

 

In short, yes assuming there were no other factors involved such as someone else stated, the wheels giving out. The plane would be moving, it would create lift and it would take off.

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I like the toy car idea.

 

 

 

For an experiment... If anyone wants to try it.

 

 

 

Take a toy car, something that the wheels move freely and put it on a moving belt, like a treadmill.

 

 

 

Have some sort of external force, your hand would be ideal for this... To keep the car from moving when the treadmill is turned on.

 

 

 

If I'm right, that should simulate no friction and no mass? Or simply the car going at the same "speed" as the treadmill. Bear with me... It's hurting my head too.

 

 

 

Turn on the treadmill and watch the wheels start to move.

 

 

 

Apply a small amount of force on the car, easily done with your hand. But it'd be better if you could add measurable force. The car should start moving forward. The reason you'd want measurable force is to eliminate you adding any extra force when you sense the speed of the treadmill increase.

 

 

 

While you're doing this, get someone to turn up the speed of the treadmill.

 

 

 

If the car continues to move forward then it can obviously create lift (if it had wings) if the car starts to move backwards or stays still, no lift can be created until you increase the force that is being exerted on the car.

 

 

 

 

 

 

 

Now that I think about it, how is the treadmill moving? The plane sits stationary until the jet engines (external force) act and propel the plane forward. So that'd mean that the treadmill is off. The plane will start moving forward due to thrust.

 

 

 

The treadmill will then measure the ground speed of the plane (Speed = Distance traveled divided by time?) and start moving in the opposite direction.

 

 

 

To be easy on you all, say on a runway the planes wheels start moving at 10 rotations per minute. If they were on an opposite moving treadmill which is also pushing the wheels in the same direction using the ground speed of the plane, this would make the wheels turn at 20 rotations per minute. So to be quite honest, in your way of thinking technically the plane should be moving forward even faster.

 

 

 

I think what everyone is trying to say when they think that the speed of the treadmill is making the plane stand still is that the treadmill is an equal force in the opposite direction, which I'm afraid it isn't.

 

 

 

You know... I think I started rambling there.

 

 

 

Here's a pretty picture to help. ^_^

 

 

 

planeontreadmillqd6.gif

 

 

 

In short, yes assuming there were no other factors involved such as someone else stated, the wheels giving out. The plane would be moving, it would create lift and it would take off.

 

 

 

You win. The treadmill would just move the wheels as you say. Now answer this, if the treadmill was going the same speed in the direction of the plane, would it take off?

I shall take my flock underneath my own wing, and kick them right the [bleep] out of the tree. If they were meant to fly, they won't break their necks on the concrete.
So, what is 1.111... equal to?

10/9.

 

Please don't continue.

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You win. The treadmill would just move the wheels as you say. Now answer this, if the treadmill was going the same speed in the direction of the plane, would it take off?

 

 

 

You mean, if the treadmill was also mobile and moving along the ground at the same ground speed as the plane?

 

 

 

The plane would still lift off as it's moving forward with the plane, thus creating lift and making it take off. :)

 

 

 

I'd draw another picture, but I'm going to bed now. I'll keep this topic in my head and maybe return to it tomorrow.

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