Plane

[Swango1980]

Ffs. I'm still thinking about it.
Isn't there some kind of paradox?
If the rotation of the wheels and the speed of the conveyor belt are constantly perfectly matched then they could be considered being geared at a 1:1 ratio, as if cogged. Therefore the plane can only move forward on the belt if its wheels are going faster than the belt. Which breaks the rules set out in the puzzle.
Doesn't it?

It is a paradox if you think the speed of the treadmill can be programmed to match the speed (but in reverse direction) that the wheels are moving in based on the direction and speed the plane wants to move. Because, the wheels on a plane can only move in the first place if the plane moved forward. If the plane remains still, the wheels will remain still. And the treadmill is only reacting to what the wheels do. So, someone could try and write a program to attempt it, but all that would happen is that the engines would propel the plane forwards, wheels start moving, treadmill starts moving, wheels move faster, treadmill moves faster. The treadmill and wheels would just continually speed up, the treadmill could never catch up and the plane would just take off as per normal.

As Crow said in post 396 (and he said it previously), the post does not actually say it is a treadmill, but a conveyor belt (which may or may not be the same thing). The conveyor belt may actually be programmed to move forwards, in the direction the plane wants to move in. This can be said to counter the wheels rotation. Therefore, the plane still moves forward as normal, the belt moves forward and the wheels simply stay still.

Both cases, the plane obviously takes off. But the treadmill / conveyor belt runs in different directions. The second option is much more practical, because the first option would just result in the treadmill having to run incredible speeds as it is chasing a speed that it can never catch up with, many many times a second.

 

[Deleted member 36735]

only yesterday you suggested a plane will dead stop if landing on a conveyor belt moving opposite to it

That was 2 days ago when I decided this was a stupid discussion.

And whilst I'm not bothering to search for what I wrote to see if I worded it badly, think of a sprinter doing the 100 metres in 10 seconds, ie 10 meters per second. If at any time during the sprint he runs onto a conveyor belt moving towards him at 10 metres per second, he keeps sprinting forward at 10 metres per second IN RELATION TO THE SURFACE UNDERNEATH HIM, however as that surface is moving at the same speed in the opposite direction, he will no longer be moving forward according to the perspective of the spectators sat in the stadium. That is exactly the same as a plane travelling at 180mph landing on a conveyor travelling at 180mph in the opposite direction, the plane will travel at 180mph in relation to the conveyor but will not be moving in relation to the fixed tarmac, that is what I meant if it wasn't obvious.

You cannot claim to be right on this, none of us can because the conundrum is worded to be deliberately misleading, just google it and you will find the same arguments going back 20 years.

 

[Deleted member 35927]

That was 2 days ago when I decided this was a stupid discussion.

And whilst I'm not bothering to search for what I wrote to see if I worded it badly, think of a sprinter doing the 100 metres in 10 seconds, ie 10 meters per second. If at any time during the sprint he runs onto a conveyor belt moving towards him at 10 metres per second, he keeps sprinting forward at 10 metres per second IN RELATION TO THE SURFACE UNDERNEATH HIM, however as that surface is moving at the same speed in the opposite direction, he will no longer be moving forward according to the perspective of the spectators sat in the stadium. That is exactly the same as a plane travelling at 180mph landing on a conveyor travelling at 180mph in the opposite direction, the plane will travel at 180mph in relation to the conveyor but will not be moving in relation to the fixed tarmac, that is what I meant if it wasn't obvious.

You cannot claim to be right on this, none of us can because the conundrum is worded to be deliberately misleading, just google it and you will find the same arguments going back 20 years.

This is where you keep going wrong and comparing it to something thats acting against the ground underneath it.
What makes a planes wheels move ?

How does newtons 2nd law fit in to this?

 

[RichA]

It is a paradox if you think the speed of the treadmill can be programmed to match the speed (but in reverse direction) that the wheels are moving in based on the direction and speed the plane wants to move. Because, the wheels on a plane can only move in the first place if the plane moved forward. If the plane remains still, the wheels will remain still. And the treadmill is only reacting to what the wheels do. So, someone could try and write a program to attempt it, but all that would happen is that the engines would propel the plane forwards, wheels start moving, treadmill starts moving, wheels move faster, treadmill moves faster. The treadmill and wheels would just continually speed up, the treadmill could never catch up and the plane would just take off as per normal.

As Crow said in post 396 (and he said it previously), the post does not actually say it is a treadmill, but a conveyor belt (which may or may not be the same thing). The conveyor belt may actually be programmed to move forwards, in the direction the plane wants to move in. This can be said to counter the wheels rotation. Therefore, the plane still moves forward as normal, the belt moves forward and the wheels simply stay still.

Both cases, the plane obviously takes off. But the treadmill / conveyor belt runs in different directions. The second option is much more practical, because the first option would just result in the treadmill having to run incredible speeds as it is chasing a speed that it can never catch up with, many many times a second.

The puzzle does not state that either conveyor or wheels are reacting. It states that they "perfectly" counteract each other.
Therefore groundspeed must always be zero until the wheels leave the conveyor belt.
Therefore whether the plane takes off depends entirely on whether one believes the engines alone can generate 180mph of airspeed across the wings.
I'm back where I started. No longer a believer.

 

[Swango1980]

You haven't actually "clarified" anything.
You and the guy that can't spell hamburger have put forward very vague descriptions without any scientific facts behind them that you claim to be proof. When you say people are "ignoring", they are actually just disagreeing with your hair-brained ideas. A modern day version of that is Trumpism at its finest.

The bottom line though, is that none of us can actually be correct.

A quick Google search shows that this conundrum has been around on the internet for nearly 2 decades, with thousands of arguments for and against the plane taking off very similar to those in this thread. The specific wording of the question makes it impossible to answer as it is vague and causes disagreement on what is actually happening, the fact that 400 posts in and people are disagreeing with the actual scenario rules is a good example of that.

From the wording of the question, nobody can categorically say that the plane will take off or that it cannot take off, and that's the whole point of the clever conundrum in the first place.

The only people who are wrong are those of us who believed one way or another, which is basically all of us

That was a lot of effort to tell us absolutely nothing about the OP. Well done.

For anyone that is interested in it, they can caveat their replies by giving their working assumptions that were not within the OP. For example, clarify that they are assuming a pilot actually engages the engines to generate thrust as per a normal take off. Or assume the conveyor belt is actually a lot longer than the picture, etc.

It isn't a clever conundrum because it is impossible to answer. It is a clever conundrum because it tricks the user into thinking the conveyor belt acts like a normal treadmill, the plane will be still, and they automatically think about how wings generate lift. They completely forget how the engine of a plane works, and that the wheels are actually passive. As I said in my very first post I believe, that was the instand conclusion I jumped to, and then I gave it more thought and realised a plane being stationary on a treadmill once it's jet engines are engaged is absurd.

Of course, it was you that claimed that a plane landing on a treadmill running at the same air speed as the plane in reverse direction would cause the plane to instantly come to rest relative to the air. I'd like to hear your vague scientific description on how that works.

 

[Deleted member 36735]

This is where you keep going wrong and comparing it to something thats acting against the ground underneath it.
What makes a planes wheels move ?

How does newtons 2nd law fit in to this?

If a plane lands on tarmac at 180 mph, are we in agreement that give or take little bit, the plane initially continues to move along the runway at 180mph for a while?

 

[RichA]

This is where you keep going wrong and comparing it to something thats acting against the ground underneath it.
What makes a planes wheels move ?

How does newtons 2nd law fit in to this?

Turn it around though.
What allows the plane to move forward when it is not airborne? The wheels.
So if the rotation of the wheels has no effect because they are always perfectly opposed by the belt, then that plane is not moving forward.

 

[Deleted member 35927]

If a plane lands on tarmac at 180 mph, are we in agreement that give or take little bit, the plane initially continues to move along the runway at 180mph for a while?

Yes then some force will act against it to slow it. I know where you're going and it makes no sense in afraid.

 

[Deleted member 35927]

Turn it around though.
What allows the plane to move forward when it is not airborne? The wheels.
So if the rotation of the wheels has no effect because they are always perfectly opposed by the belt, then that plane is not moving forward.

You're getting hung up on the wheels part again . Planes do not need wheels, they are simply the best thing to use for minimal resistance on a runway. How do ski planes work ?

 

[Swango1980]

The puzzle does not state that either conveyor or wheels are reacting. It states that they "perfectly" counteract each other.
Therefore groundspeed must always be zero until the wheels leave the conveyor belt.
Therefore whether the plane takes off depends entirely on whether one believes the engines alone can generate 180mph of airspeed across the wings.
I'm back where I started. No longer a believer.

Hence Crowes description fits best. The treadmill is working in the direction of flight.

Because, if it operates in the direction of a normal treadmill, it is impossible for the wheels and treadmill to operate at the same speed if the plane attempts to take off as a plane would normally take off. The only way the plane could stay stationary is if the engines directly drove the wheels.

 

[Beezerk]

It’s such a poorly worded question no wonder we are on to page 21

Original question with a conveyor just big enough to fit the plane on as in the photo, for me no it won’t take off it will just fall off the end of the conveyor lol.

 

[RichA]

You're getting hung up on the wheels part again . Planes do not need wheels, they are simply the best thing to use for minimal resistance on a runway. How do ski planes work ?

You keep saying that, but the wheels are a red herring regardless which side of their involvement (or lack of) one sits.
If the puzzle had a ski plane then the conveyor belt would move to perfectly oppose horizontal motion of the skis. Therefore the plane would remain perfectly stationary with zero ground speed.

The puzzle is basically whether a plane can generate takeoff airspeed purely using its propulsion system.
Everything else is just designed to create a distraction.

 

[Deleted member 36735]

Hence Crowes description fits best. The treadmill is working in the direction of flight.

If you have a definitive view, it must derive from the exact scenario. So as said scenario is only a few words long, can you exactly quote them so we all know why you think the treadmill is going in the same direction as the plane?

 

[sunshine]

Of course, we've already clarified that the plane moves forwards. You either missed that, or conveniently ignoring to for motivations unknown to me?

No, you are getting confused again, and making up all sorts of variations. Go back to the original post.

 

[Deleted member 35927]

You keep saying that, but the wheels are a red herring regardless which side of their involvement (or lack of) one sits.
If the puzzle had a ski plane then the conveyor belt would move to perfectly oppose horizontal motion of the skis. Therefore the plane would remain perfectly stationary with set ground speed.

The puzzle is basically whether a plane can generate takeoff airspeed purely using its propulsion system.
Everything else is just designed to create a distraction.

In order for the planes wheels to move it must be moving forwards under the power of the jets . The wheels have no drive of there own.
Once something is moving you need opposing force to slow it. Where is that force coming from ?

 

[Deleted member 36735]

It’s such a poorly worded question no wonder we are on to page 21

Yes exactly, it's been on the internet for almost 2 decades and we all fell for it .

I now know I was wrong to have a steadfast view one way or the other, if others want to believe they are right without researching the actual meme and it's internet presence then up to them.

 

[Deleted member 35927]

No, you are getting confused again, and making up all sorts of variations. Go back to the original post.

It would make no difference what the direction of the conveyor is . Plane takes off.

 

[RichA]

In order for the planes wheels to move it must be moving forwards under the power of the jets . The wheels have no drive of there own.
Once something is moving you need opposing force to slow it. Where is that force coming from ?

Seriously? The conveyor belt that perfectly opposes the rotation of the plane's wheels (or forward motion of its skis).
It has to be powered to do that.

I think you and Swango are assuming that the conveyor belt is a passive, frictionless mechanism (like the wheels) that the plane's propulsion system just overpowers.

 

[Deleted member 35927]

Seriously? The conveyor belt that perfectly opposes the rotation of the plane's wheels (or forward motion of its skis).
It has to be powered to do that.

I think you and Swango are assuming that the conveyor belt is a passive, frictionless mechanism (like the wheels) that the plane's propulsion system just overpowers.

The wheels are passive , this is true of planes in general .
How does the conveyor interact with the wheels in order to slow the plane, the planes wheels only rotate because the plane is moving.

 

[Swango1980]

If you have a definitive view, it must derive from the exact scenario. So as said scenario is only a few words long, can you exactly quote them so we all know why you think the treadmill is going in the same direction as the plane?

I have already done so, when explaining how that assumption can fit. Crow has also done so, so you can ask him. Perhaps you can send him a PM to discuss it fully, if you are unable to grasp the words he has already posted