Neutered, do the skateboard experiment I posted about earlier, it will help you understand that no matter how fast the treadmill is going, the plane on the treadmill will go just as fast as a plane on a conventional runway using the same amount of thrust.

 

I understand that the plane will take off. I never EVER said that it was impossible. In fact, my first post even states that it will.

I was making the point that there has to be enough thrust to overcome the friction acting on the wheels.

 

You know my statement is true though. Treadmill or no treadmill you still need proper speed to generate lift.

Unless you are Superman of course.

 

I did this yesterday and I have an appointment with my chyropractor.

 

Let's say there's enough friction to create about 200 lbs of drag between the plane and the ground/treadmill its setting on. (I think that's a reasonable real-world estimate, given that a strong man can pull a 737 accross the tarmac.) So in that situation, do you think there's anything that a treadmill can do to prevent a plane at full throttle from taking off?

 

Wind speed does affect friction. The faster you go, the more friction from the air. In fact, the friction rises as a square function of the wind speed. You go twice as fast, there's 4x more friction. The result is that if you want to go twice as fast...you need 8x the power. That's why some jets put out hundreds of thousands of horsepower and still only do ~600mph.

It does not work this way with rolling friction. You go faster...friction stays the same. You go twice as fast...friction stays the same. In fact, I think it actually can go down at some point. So the point is that a plane sitting on a 100000mph conveyor sees the same friction as if that conveyor was going 10mph. And since the plane is not actually moving, it sees no friction from the air....

 

...but you DID say:

Plane < 10 mph
Treadmill > 10 mph
= Plane 0 mph

...and that simply isn't the case. End of story. No semantics, no wordplay. You were incorrect to say that. Own up.

 

[QUOTE=Neutered Sputniks,Feb 10 2008, 02:39 AM] Wow....lol, there are some physics geniuses in here

It all depends on the airplane's ground speed, not wheel speed.

 

i got what he was saying after he said he meant wheel speed not ground speed, and he was a little unclear about it. but this thread has been so strung out, all we wanted to know is if the plane would take off. YES. why cant the thread end with that.

we don't need someone coming in here rolling their eyes at us telling us he is an engineer from some aeronautical spot that a plane that has 0 groundspeed is not going to take off because that is obvious and completely argumentative at this point in the thread. why even mention that? to prove what, that a plane will not take off with a groundspeed of 0, no kidding, but how likely is that?

this is how i interpret it. he basically says... "you guys suck at physics. sure a plane can take off on a treadmil but you fail to realize that if it is on a treadmill and the plane boosts itself to just overcome the friction of the wheels and has 0 groundspeed its not going to take off." no kidding, but was that necessary to really say at this point?

 

True...