You have a plane and a conveyor belt.

[JujuFish]

Originally posted by: NanoStuff
Again, let's look at the cogs, one begins to rotate and the other rotates instantly

Yes, and both the plane wheels and conveyor belt can be rotating simultaneously. That won't, however, keep the plane stationary.

 

[NanoStuff]

Originally posted by: JujuFish

Originally posted by: NanoStuff
Again, let's look at the cogs, one begins to rotate and the other rotates instantly

Yes, and both the plane wheels and conveyor belt can be rotating simultaneously. That won't, however, keep the plane stationary.

Seems to me that it would, as the wheels of the plane would have to be rotating faster in order for it to advance forward, yet the question states; if you interprate it as such, that this will not happen.

 

[NanoStuff]

-double post-

 

[JujuFish]

Originally posted by: NanoStuff

Originally posted by: JujuFish

Originally posted by: NanoStuff
Again, let's look at the cogs, one begins to rotate and the other rotates instantly

Yes, and both the plane wheels and conveyor belt can be rotating simultaneously. That won't, however, keep the plane stationary.

Seems to me that it would, as the wheels of the plane would have to be rotating faster in order for it to advance forward.

No, they wouldn't. In fact, the conveyor would always be moving as fast relative to the wheels as the wheels would be relative to the conveyor. Even if the conveyor is stationary.

 

[NanoStuff]

Originally posted by: JujuFish

Originally posted by: NanoStuff

Originally posted by: JujuFish

Originally posted by: NanoStuff
Again, let's look at the cogs, one begins to rotate and the other rotates instantly

Yes, and both the plane wheels and conveyor belt can be rotating simultaneously. That won't, however, keep the plane stationary.

Seems to me that it would, as the wheels of the plane would have to be rotating faster in order for it to advance forward.

No, they wouldn't. In fact, the conveyor would always be moving as fast relative to the wheels as the wheels would be relative to the conveyor. Even if the conveyor is stationary.

More room for interpretation I see.

The belt compensates for the rotation of the wheels in reverse

By compensate you should assume it's not just relativity to the wheels, the belt DOES move backwards relative to the world.

 

[JujuFish]

Originally posted by: NanoStuff

The belt compensates for the rotation of the wheels in reverse

By compensate you should assume it's not just relativity to the wheels, the belt DOES move backwards relative to the world.

Ah, but if it's relative to the world then it applies a torque to the wheels and will never achieve exact compensation. As in your cog example, if you have two different sized cogs, they will never rotate at the same speed.

 

[mugs]

Originally posted by: NanoStuff

Originally posted by: mugs
in order for the treadmill to start moving at all, the plane must move forward

In the real-world there will be a certain latency before the belt can compensate for the rotation of the wheel, yes, but in the real world a belt could also predict what the speed of the wheel will be and prevent under-compensation. Those are just unnecessary complications, you just assume the belt will compensate exactly thus it would at no point move faster or slower than the rotation of the wheels. No paradox there, just an instantaneous response.

Again, let's look at the cogs, one begins to rotate and the other rotates instantly (now you can argue that there's material compression and compression propagation, and you'd be right, but that's not part of the question)

So granting all of that, the only reason it can't take off is that people say the wheels will be destroyed. How do we know the conveyor belt is even capable of achieving that speed? And if we can design a conveyor belt that can reach such speeds, surely we can make wheels and tires that will handle equal speeds, right? And even if the wheels fall off, at some point they will come to a rest and the conveyor belt will stop. At that point all the plane needs is sufficient thrust to take off without wheels. You said we have infinite thrust, remember. And even if you say all of that cannot happen for whatever reason, there is still the perfectly valid reason I have given in this and other threads that the plane could take off - all it needs is sufficient airflow over the wings. That could come from the motion of the plane through the air OR the motion of the air past the plane. Big gust of wind = plane stays up. There's also the equally valid solution that has been posted elsewhere in this thread - all you need is to get the plane tilting upwards a little bit and your infinite thrust will launch you space shuttle style. Put a bunch of weight at the back of the plane and you take off.

In other words, your version of the question sucks, which is why so many people are ignoring it and discussing the proper version of the question.

 

[NanoStuff]

Originally posted by: JujuFish

Originally posted by: NanoStuff

The belt compensates for the rotation of the wheels in reverse

By compensate you should assume it's not just relativity to the wheels, the belt DOES move backwards relative to the world.

Ah, but if it's relative to the world then it applies a torque to the wheels and will never achieve exact compensation. As in your cog example, if you have two different sized cogs, they will never rotate at the same speed.

The larger cog would take longer to make a rotation, but the surface speed of both would be the same.

Originally posted by: mugs
In other words, your version of the question sucks, which is why so many people are ignoring it and discussing the proper version of the question.

There is no proper version of the rotating wheels interpretation. I'm well aware the outcome could differ if one makes assumptions. Might be a whole lot easier if you don't add your own variables and just assume a typical real-world plane to be on that belt.

 

[blahblah99]

For all the dumbasses that don't think the plane will go anywhere, go look up F=MA. Draw the free body diagram of all the forces acting on the plane and you will see why the plane will take off. In fact, just do it for the horizontal axis and you will see the plane will accelerate.

Now quit arguing, cause it's obvious you guys didn't pay attention or take physics in school.

I can put this problem into a state-space model, but there's no point in doing that if some of you can't even understand F=MA.

 

[JujuFish]

Originally posted by: NanoStuff
The larger cog would take longer to make a rotation, but the surface speed of both would be the same.

As it would be regardless of what the conveyor is doing.

 

[NanoStuff]

Originally posted by: JujuFish

Originally posted by: NanoStuff
The larger cog would take longer to make a rotation, but the surface speed of both would be the same.

As it would be regardless of what the conveyor is doing.

Right, thus the belt cancels out the forward rotation of the wheel.

 

[JujuFish]

Originally posted by: NanoStuff

Originally posted by: JujuFish

Originally posted by: NanoStuff
The larger cog would take longer to make a rotation, but the surface speed of both would be the same.

As it would be regardless of what the conveyor is doing.

Right, thus the belt cancels out the forward rotation of the wheel.

Take a look at the bolded word. The conveyor would have no appreciable effect.

 

[jagec]

Originally posted by: NanoStuff

Originally posted by: mugs
In other words, your version of the question sucks, which is why so many people are ignoring it and discussing the proper version of the question.

There is no proper version of the rotating wheels interpretation. I'm well aware the outcome could differ if one makes assumptions. Might be a whole lot easier if you don't add your own variables and just assume a typical real-world plane to be on that belt.

no, there is ONE interpretation. The conveyor moves backwards as the wheels move FORWARD. FORWARD means in a linear, not angular direction. A wheel that is spinning in place is obviously NOT moving forward at all. The only way anyone could ever THINK it was moving "forward" would be with respect to the conveyor, but that makes absolutely no sense since the conveyor cannot move "backwards" in its own reference frame. So OBVIOUSLY the OP is posted with respect to a stationary reference frame. One in which the conveyor moves backwards, and the wheels--attached to the plane--move forward, with respect to the GROUND. Thus, the plane takes off.

 

[NanoStuff]

Originally posted by: jagec

Originally posted by: NanoStuff

Originally posted by: mugs
In other words, your version of the question sucks, which is why so many people are ignoring it and discussing the proper version of the question.

There is no proper version of the rotating wheels interpretation. I'm well aware the outcome could differ if one makes assumptions. Might be a whole lot easier if you don't add your own variables and just assume a typical real-world plane to be on that belt.

no, there is ONE interpretation. The conveyor moves backwards as the wheels move FORWARD. FORWARD means in a linear, not angular direction.

That is the original question, and yes the plane takes off in this case.

 

[mugs]

Originally posted by: NanoStuff

Originally posted by: mugs
In other words, your version of the question sucks, which is why so many people are ignoring it and discussing the proper version of the question.

There is no proper version of the rotating wheels interpretation. I'm well aware the outcome could differ if one makes assumptions. Might be a whole lot easier if you don't add your own variables and just assume a typical real-world plane to be on that belt.

Sure, as long as you assume a typical real-world conveyor belt that is not capable of accelerating to infinite speed. If you take that out of the equation the plane would take off just fine.

There is no proper version of the rotating wheels interpretation because the rotation wheels version is wrong to begin with!

 

[Xkaliber]

The plane would have to be going faster than the speed of light to take off. Doing so would cause the passengers in the plane to travel back in time to a period when planes did not exist. Consequently, a universal paradox would be created. This is why the plane would not take off.

 

[Schfifty Five]

Awesome thread.

 

[Glavinsolo]

Originally posted by: PowerMacG5

Originally posted by: NanoStuff

Originally posted by: PowerMacG5

Originally posted by: FeuerFrei
You freaks who somehow convinced yourself it would take off need to go back and read the OP. The conveyor is moving backwards while the plane rolls forward, COMPLETELY NEGATING any forward progress the plane would make. The conveyor would speed up to match the increasing thrust of the plane and thus the motion of the plane would be imperceptible and airspeed would = 0. Basically, the plane is static in airspace and the ground is moving beneath it... that is all.

This thread is not for arguing whether a plane could take off on a conveyor belt, PERIOD. Naturally a plane would eventually accellerate enought to achieve airspeed (if the conveyor stayed at a constant pace) it would just take longer to launch.

Ok, you are an idiot. The plane does not use it's wheels for motion.

Assuming the plane has get engines:
It uses the jet engines. The jets do not give a fvck what the ground is doing. With a plane, you have to realize there are basically two roads. The ground and the air. Your car is moving using the ground, the plane the air. The jets push on the air, not the ground. If you still feel you are correct, think of it this way. A car cannot drive well on the ice, but a plane can take off perfectly fine, traveling in a perfectly straight line.

If you don't believe me, then you are a fvcking moron who will get no where in life because he doesn't understand a basic thing. I am sick of all these morons here not understanding basic physics.

You might want to be careful with what you say. I'm sure you'd feel ridiculous if you realized you were wrong after all that.

The belt does not care what the source of propulsion is, a car would behave the same way on that belt. The belt just senses rotation of the wheels and compensates for this, regardless of what force is rotating them. If the wheel cannot rotate faster than the belt is moving backwards, the wheel would effectively be stationary to the world around it. Because the plane is attached to it's wheels, the plane would likewise remain in the same spot.

A loss of traction would be required for the plane to take off.

The reason I won't feel ridiculous is because I am 100% correct.

Imagine this. Bush pilots airplanes right on sleds, not wheels. Sleds do not rotate, and are in effect "stationary." Guess what, these planes still take off.

The only thing wheels do for an airplane is provide an interface to the ground so the plane is not rubbing its belly (simplified for takeoff only, and I know thats not the only purpose when it comes to landing, but we are talking takeoff).

As long as the wheels are not literally clamped to the ground, it doesnt matter how fast the ground is moving, the wheels will just turn at incredible speeds while the plane moves through the air.

PowerMacG5 is correct along with everyone else who said it would take off.

What gets a plane moving are its propellers or jet turbines, which shove the air backward and thereby impel the plane forward. What the wheels, conveyor belt, etc, are up to is largely irrelevant. Let me repeat: Once the pilot fires up the engines, the plane moves forward at pretty much the usual speed relative to the ground--and more importantly the air--regardless of how fast the conveyor belt is moving backward. This generates lift on the wings, and the plane takes off. All the conveyor belt does is, as you correctly conclude, make the plane's wheels spin madly.

Cars and planes don't work the same way.

 

[NanoStuff]

Originally posted by: Glavinsolo

Originally posted by: PowerMacG5

Originally posted by: NanoStuff

Originally posted by: PowerMacG5

Originally posted by: FeuerFrei
You freaks who somehow convinced yourself it would take off need to go back and read the OP. The conveyor is moving backwards while the plane rolls forward, COMPLETELY NEGATING any forward progress the plane would make. The conveyor would speed up to match the increasing thrust of the plane and thus the motion of the plane would be imperceptible and airspeed would = 0. Basically, the plane is static in airspace and the ground is moving beneath it... that is all.

This thread is not for arguing whether a plane could take off on a conveyor belt, PERIOD. Naturally a plane would eventually accellerate enought to achieve airspeed (if the conveyor stayed at a constant pace) it would just take longer to launch.

Ok, you are an idiot. The plane does not use it's wheels for motion.

Assuming the plane has get engines:
It uses the jet engines. The jets do not give a fvck what the ground is doing. With a plane, you have to realize there are basically two roads. The ground and the air. Your car is moving using the ground, the plane the air. The jets push on the air, not the ground. If you still feel you are correct, think of it this way. A car cannot drive well on the ice, but a plane can take off perfectly fine, traveling in a perfectly straight line.

If you don't believe me, then you are a fvcking moron who will get no where in life because he doesn't understand a basic thing. I am sick of all these morons here not understanding basic physics.

You might want to be careful with what you say. I'm sure you'd feel ridiculous if you realized you were wrong after all that.

The belt does not care what the source of propulsion is, a car would behave the same way on that belt. The belt just senses rotation of the wheels and compensates for this, regardless of what force is rotating them. If the wheel cannot rotate faster than the belt is moving backwards, the wheel would effectively be stationary to the world around it. Because the plane is attached to it's wheels, the plane would likewise remain in the same spot.

A loss of traction would be required for the plane to take off.

The reason I won't feel ridiculous is because I am 100% correct.

Imagine this. Bush pilots airplanes right on sleds, not wheels. Sleds do not rotate, and are in effect "stationary." Guess what, these planes still take off.

The only thing wheels do for an airplane is provide an interface to the ground so the plane is not rubbing its belly (simplified for takeoff only, and I know thats not the only purpose when it comes to landing, but we are talking takeoff).

As long as the wheels are not literally clamped to the ground, it doesnt matter how fast the ground is moving, the wheels will just turn at incredible speeds while the plane moves through the air.

PowerMacG5 is correct along with everyone else who said it would take off.

What gets a plane moving are its propellers or jet turbines, which shove the air backward and thereby impel the plane forward. What the wheels, conveyor belt, etc, are up to is largely irrelevant. Let me repeat: Once the pilot fires up the engines, the plane moves forward at pretty much the usual speed relative to the ground--and more importantly the air--regardless of how fast the conveyor belt is moving backward. This generates lift on the wings, and the plane takes off. All the conveyor belt does is, as you correctly conclude, make the plane's wheels spin madly.

Cars and planes don't work the same way.

Where the thrust comes from is irrelevant, a car would behave the same way on the conveyor belt. The origin of the power is irrelevant if the wheels hold traction with the belt.

 

[JujuFish]

Originally posted by: NanoStuff
Where the thrust comes from is irrelevant, a car would behave the same way on the conveyor belt. The origin of the power is irrelevant if the wheels hold traction with the belt.

So, so very wrong.

 

[NanoStuff]

Originally posted by: JujuFish

Originally posted by: NanoStuff
Where the thrust comes from is irrelevant, a car would behave the same way on the conveyor belt. The origin of the power is irrelevant if the wheels hold traction with the belt.

So, so very wrong.

I know it's not, but I'd love to hear your argument as I do enjoy it.

 

[AbAbber2k]

Ok I figured out how to solve this argument once and for all. Two planes are already in flight. One plane has a giant conveyor belt on top moving backwards at a speed equal to the plane's forward momentum. The other plane is moving at the same speed as the first, lowers it's landing gear and gently touches down on top of the convery. Does the second plane immediatly cease to move forward and plument to it's ultimate demise?



And to take it a step further, does the 2nd plane's contact push the 1st forward even faster because of the effects of the conveyor?

 

[JujuFish]

Originally posted by: NanoStuff

Originally posted by: JujuFish

Originally posted by: NanoStuff
Where the thrust comes from is irrelevant, a car would behave the same way on the conveyor belt. The origin of the power is irrelevant if the wheels hold traction with the belt.

So, so very wrong.

I know it's not, but I'd love to hear your argument as I do enjoy it.

Well, I started at about page 14. You can go back from there and read, if you'd like.

 

[Mo0o]

This of it this way. You are lying on a skateboard thats attached to a rope that's slowly being wound by an spindle. You place the skateboard on one of those airport rolling walkways. Assuming the spindle is not moving, you would stay in place while the wheels begin to roll. If you start increasing the speed of the conveyor belt, the tension might increase a little but the skateboard would not move. Now start winding the spindle. Assuming the axel has enough hp , the skateboard WILL move forward no matter how fast this conveyor belt is moving. The only instance where the skateboard might not move is if there is a ridiculously high coefficeint of friction either between the wheel and the ground or between the axel of the wheel and the wheel itself. But ignoring those, which don't exist, the rotating axil outside of the belt WILL move the skateboard forward virtually independent of the movement of the conveyor belt.

 

[NanoStuff]

Well then, I don't need to go further than page 14. This Tom fella is correct. If the wheels rotate forward at speed x and the belt rotates backwards at speed x, the outcome is quite obvious that the wheel would remain stationary to an observer regardless of what is attached to it and what force induced rotation on that wheel. If wheel rotation is x(2) and belt speed is x; as would be the case if the belt matched the speed of the plane, the plane would be capable of accelerating forward and thus taking off, but would require approximately twice the power to do so.