Plane on a Treadmill

[cmoneyr]

Otherwise the question would be more simply put - can a treadmill matching the speed of the wheels of the plane keep a plane from moving forward?

First, that's not the spirit of the problem. It's not asking if a treadmill can keep a plane from moving, obviously if a treadmill could move infinitely fast it could do that. The idea is that on a treadmill moving the same speed as a plane, can a plane take off?

Second, matching the speed of the wheels is impossible. If plane is moving at 30mph the wheels move at 30mph. Add a treadmill now doing 30mph, but then the wheels are now going 60mph. Bump up treadmill to 60mph, now wheels are doing 90mph. Treadmill now going 90mph, wheels compensate and go 120mph, it never ends. But, once again, that's not what the question is asking.

 

[CyinCo]

First, that's not the spirit of the problem. It's not asking if a treadmill can keep a plane from moving, obviously if a treadmill could move infinitely fast it could do that. The idea is that on a treadmill moving the same speed as a plane, can a plane take off?

Second, matching the speed of the wheels is impossible. If plane is moving at 30mph the wheels move at 30mph. Add a treadmill now doing 30mph, but then the wheels are now going 60mph. Bump up treadmill to 60mph, now wheels are doing 90mph. Treadmill now going 90mph, wheels compensate and go 120mph, it never ends. But, once again, that's not what the question is asking.

Correct, the equation contains a circular reference.

 

[Hilz4cy]

This could go on forever, until they do the darn thing and prove it one way or the other. There is no other research out regarding this =). I not attempting to rehash the prevoius 500 postings just thought we can't be the first to be dicussing this, This had to be on some physics final somehwhere.

 

[DaddyMac]

First, that's not the spirit of the problem. It's not asking if a treadmill can keep a plane from moving, obviously if a treadmill could move infinitely fast it could do that. The idea is that on a treadmill moving the same speed as a plane, can a plane take off?

Second, matching the speed of the wheels is impossible. If plane is moving at 30mph the wheels move at 30mph. Add a treadmill now doing 30mph, but then the wheels are now going 60mph. Bump up treadmill to 60mph, now wheels are doing 90mph. Treadmill now going 90mph, wheels compensate and go 120mph, it never ends. But, once again, that's not what the question is asking.

And I don't think the "spirit" of the problem is relying on a near mile long treadmill, nor the possibility of the plane moving OFF the treadmill.

 

[Hilz4cy]

By the way thanks for the welcome, I have been reading many of the threads mostly surronding the sports topics but this one seemed interesting. I don't know how much I will post but it is a very amusing site. and nice to speak with like, sound minded people (cyclones) once in while =), thanks again.

 

[cmoneyr]

This could go on forever, until they do the darn thing and prove it one way or the other. There is no other research out regarding this =). I not attempting to rehash the prevoius 500 postings just thought we can't be the first to be dicussing this, This had to be on some physics final somehwhere.

Most all places on the internet that have discussed this have come to the overwhelming conclusion that the plane will take off.

 

[cmoneyr]

And I don't think the "spirit" of the problem is relying on a near mile long treadmill, nor the possibility of the plane moving OFF the treadmill.

If you reread post #1 you will see we are assuming an "infinitely long treadmill"

 

[htownclone]

Who thinks a plane would be able to take off if it were not moving forward on the treadmill, assuming that the plane and belt are moving the same speed and the plane is neither moving backwards or forwards. So the plane is moving as fast as you want it to...

 

[DaddyMac]

If you reread post #1 you will see we are assuming an "infinitely long treadmill"

Well that's just dumb. Why the hell would you have an "infinitely long treadmill"?

And how would you test that?

My mistake then - I was just going down the normal treadmill idea.

 

[CyPlainsDrifter]

First, that's not the spirit of the problem. It's not asking if a treadmill can keep a plane from moving, obviously if a treadmill could move infinitely fast it could do that. The idea is that on a treadmill moving the same speed as a plane, can a plane take off?

Second, matching the speed of the wheels is impossible. If plane is moving at 30mph the wheels move at 30mph. Add a treadmill now doing 30mph, but then the wheels are now going 60mph. Bump up treadmill to 60mph, now wheels are doing 90mph. Treadmill now going 90mph, wheels compensate and go 120mph, it never ends. But, once again, that's not what the question is asking.

I think you're a tad off on that second part.... in essence, you are correct, but there is a point very early on where the wheel speed and the threadmill speed could match. Consider this......

The plane is sitting on the threadmill and the threadmill starts moving first. Would the plane sit still? No. It would move with the treadmill, due to the friction in the bearings. The wheels may start moving and maybe not, but the net loss is in the friction, and thus a net backward motion of the plane.

Now, if you could provide a very small amount of thrust, measured precisely to overcome this friction ONLY, the plane would sit still in space and the wheel speed of the plane would equal the treadmill belt speed and the plane would be motionless. Clearly, this tiny amount of thrust, would be impossible to achieve. This would be equivalent to the force from the string tied to a shopping cart in a much earlier example.

Just a small point of order.... doesn't really mean much in the grand scheme of the problem.

 

[CyPlainsDrifter]

And I don't think the "spirit" of the problem is relying on a near mile long treadmill, nor the possibility of the plane moving OFF the treadmill.

Well, if the plane was unable to move forward, the treadmill would not need to be long at all. That's why the original question states "infinity long".....

 

[CyPlainsDrifter]

Who thinks a plane would be able to take off if it were not moving forward on the treadmill, .

No one!

...... assuming that the plane and belt are moving the same speed and the plane is neither moving backwards or forwards.

You're either still not listening, or you are not thinking this through. The plane DOES move forward. Period, end of story.

 

[cmoneyr]

I think you're a tad off on that second part.... in essence, you are correct, but there is a point very early on where the wheel speed and the threadmill speed could match. Consider this......

The plane is sitting on the threadmill and the threadmill starts moving first. Would the plane sit still? No. It would move with the treadmill, due to the friction in the bearings. The wheels may start moving and maybe not, but the net loss is in the friction, and thus a net backward motion of the plane.

Now, if you could provide a very small amount of thrust, measured precisely to overcome this friction ONLY, the plane would sit still in space and the wheel speed of the plane would equal the treadmill belt speed and the plane would be motionless. Clearly, this tiny amount of thrust, would be impossible to achieve. This would be equivalent to the force from the string tied to a shopping cart in a much earlier example.

You are correct, but I didn't take that into account since it doesn't really fit with the problem. The problem is assuming that the plane is trying to take off, so obviously the thrust would be much more than that.

 

[htownclone]

The plane DOES move forward. Period, end of story.

/disagree :no:

 

[CyPlainsDrifter]

You are correct, but I didn't take that into account since it doesn't really fit with the problem. The problem is assuming that the plane is trying to take off, so obviously the thrust would be much more than that.

I know.... it's a miniscule part of the overall question really. Just thought I'd throw it out there to make things even more confusing ......

:biglaugh::biglaugh::biglaugh:

 

[CyPlainsDrifter]

/disagree :no:

Sorry you are wrong, wrong, wrong.

So science teacher, you still haven't answered the question...... What force is acting on the plane and how, in order to cancel out the thrust of the engines and thus deter it's forward motion. Try to give us something a little deeper than, "the treadmill is doing it." Attempt to explain the "HOW" of your conclusion.

 

[CyinCo]

/disagree :no:

I posted this earlier...

The wheels and the treadmill have nothing to do with it. Visualize a plane that can magically hover above the treadmill with no wheels at the same height as a plane with wheels. The hovering provides no lift or thrust. It just keeps the plane off the ground and allows for free movement forward and backwards. Turn on the treadmill. Fire up the engines. As the plane goes faster forward, the treadmill goes the same speed backwards. In this case, does the treadmill have any affect on the plane? I assume you'll say no. The hovering allows for free movement and decouples the plane from the motion of the treadmill. Now add the wheels back in. The wheels do what? They allow for free movement and decouple the plane from the treadmill; the same as the magic hovering situation.

 

[CyPlainsDrifter]

I'm done for now guys (it's been fun)..... someone tag me and take my place in the ring. You can try to convince the Flat Earth Society members for a while.

:wink:

 

[CyinCo]

I'm done for now guys (it's been fun)..... someone tag me and take my place in the ring. You can try to convince the Flat Earth Society members for a while.

I'm out too. I've gotta get some work done.

 

[tim_redd]

Did you happen to send this note?