So...about that plane on the treadmill...

"Peter Duniho" wrote in message
...
"Darkwing" theducksmailATyahoo.com wrote in message
...
This looks like a job for the MythBusters!!!

*Yawn*

That would be a boring show. Either they'd have to fill 19 minutes with
the construction of the treadmill itself, or they'd have the airplane
taking off in the first 30 seconds, leaving them with 19 minutes of filler
at the end.

You don't need MythBusters. You just need a little knowledge of physics
and some common sense.

Pete


Okay Mr. Cynical, I sent an email off to the Mythbusters explaining this
whole thing and a link to the Google Groups thread so we'll see if they pick
it up and show it on the program.

---------------------------
DW

It's not meaningless in the sense we can't
understand the equality being stated.

Yes it is. That's exactly the sense in which it is meaningless.

Jose
--
"There are 3 secrets to the perfect landing. Unfortunately, nobody knows
what they are." - (mike).
for Email, make the obvious change in the address.

"Darkwing" theducksmail"AT"yahoo.com wrote in message
...
So lets say I know my little RC plane takes off at exactly 25mph. So I
crank up the treadmill to step up to 25mph so I can keep the RC plane up
on the treadmill, the plane is completely stationary in regards to anyone
standing next to the plane but when the treadmill hits 25mph and my little
RC plane is staying even with the treadmill you are telling me I can pull
back on the elevator stick and the plane will take off? I don't think so.

The scenario you suggest is impossible. The RC plane will accelerate
regardless of how fast the treadmill is running. Your "little RC plane"
will NOT be "staying even with the treadmill". It will take off, just as it
would from a normal runway surface.

And it doesn't take a video of such an attempt to prove it. All it takes is
a person who has a minimal education in physics and (key point here) is
willing to listen until they understand, and someone else willing to explain
it. You clearly fail to meet either the first or second criteria, or
possibly both, since we do have the third criteria met here in the
newsgroup.

You are disrespectful of the various posters here who have made an honest
effort to explain the situation to you and others. This is because you
refuse to bother to read the wealth of information on the topic that already
exists. Until you have done so, it would be a waste of time for anyone to
bother responding to any more of your assertions or questions. I know that
I won't.

Pete

"T o d d P a t t i s t" wrote in message
news
[...]
Agreed, further interpretation is required, although I think
the most reasonable interpretation is pretty clear

But that's my point. Just as a "reasonable interpretation" is required, one
can just as easily assert that a MORE reasonable interpretation would be to
assume the question means to discuss a scenario that is at least
theoretically possibly to reproduce with existing technology.

The question is ambiguous no matter how one looks at it. How can anyone
assert that it makes more sense to interpret it in a way that creates a
physically impossible situation than to interpret in a way that can at least
in theory be tested experimentally?

Pete

"Darkwing" theducksmail"AT"yahoo.com wrote in message
...

"Brian" wrote in message
ups.com...

The only way the treadmill can stop or slow the airplane is to create
more Drag than Thrust.

The reason the airplane will be able to accelerate is that the
treadmill does not create any significant drag aircraft.

When the treadmill hits 500MPH how much force will it take to hold the
airplane in position?

With perfect frictionless bearings it will take 0 force. If the engine
is generating any thrust the airplane will move forward no matter what
the treadmill does.

Brian.


So lets say I know my little RC plane takes off at exactly 25mph. So I
crank up the treadmill to step up to 25mph so I can keep the RC plane up
on the treadmill, the plane is completely stationary in regards to anyone
standing next to the plane but when the treadmill hits 25mph and my little
RC plane is staying even with the treadmill you are telling me I can pull
back on the elevator stick and the plane will take off? I don't think so.

------------------------------------
DW


If the plane will take off at 25mph and you are standing on the treadmill
holding the plane, when the treadmill reaches 25 mph the plane will fly if
you let go of the plane.

If the engine on the plane is set to the proper power it will continue to
fly right beside you.

"Peter Duniho" wrote in message
...
"Darkwing" theducksmail"AT"yahoo.com wrote in message
...
So lets say I know my little RC plane takes off at exactly 25mph. So I
crank up the treadmill to step up to 25mph so I can keep the RC plane up
on the treadmill, the plane is completely stationary in regards to anyone
standing next to the plane but when the treadmill hits 25mph and my
little RC plane is staying even with the treadmill you are telling me I
can pull back on the elevator stick and the plane will take off? I don't
think so.

The scenario you suggest is impossible. The RC plane will accelerate
regardless of how fast the treadmill is running. Your "little RC plane"
will NOT be "staying even with the treadmill". It will take off, just as
it would from a normal runway surface.

And it doesn't take a video of such an attempt to prove it. All it takes
is a person who has a minimal education in physics and (key point here) is
willing to listen until they understand, and someone else willing to
explain it. You clearly fail to meet either the first or second criteria,
or possibly both, since we do have the third criteria met here in the
newsgroup.

You are disrespectful of the various posters here who have made an honest
effort to explain the situation to you and others.

Man you are a dick. This has NOT been adequately explained or there would be
no question about it. If the plane is not moving on the treadmill but rather
keeping up with the speed that the treadmill is moving (yes planes DO have
throttle controls) the thing is going to takeoff with no air moving over the
wings? NO WAY.

This is because you refuse to bother to read the wealth of information on
the topic that already exists. Until you have done so, it would be a waste
of time for anyone to bother responding to any more of your assertions or
questions. I know that I won't.

Pete


Thank God for that, because you are a prick. Oh yeah, *PLONK*!

-------------------------------------------
DW

"Gig 601XL Builder" wrDOTgiaconaATcox.net wrote in message
...

"Darkwing" theducksmail"AT"yahoo.com wrote in message
...

"Brian" wrote in message
ups.com...

The only way the treadmill can stop or slow the airplane is to create
more Drag than Thrust.

The reason the airplane will be able to accelerate is that the
treadmill does not create any significant drag aircraft.

When the treadmill hits 500MPH how much force will it take to hold the
airplane in position?

With perfect frictionless bearings it will take 0 force. If the engine
is generating any thrust the airplane will move forward no matter what
the treadmill does.

Brian.


So lets say I know my little RC plane takes off at exactly 25mph. So I
crank up the treadmill to step up to 25mph so I can keep the RC plane up
on the treadmill, the plane is completely stationary in regards to anyone
standing next to the plane but when the treadmill hits 25mph and my
little RC plane is staying even with the treadmill you are telling me I
can pull back on the elevator stick and the plane will take off? I don't
think so.

------------------------------------
DW


If the plane will take off at 25mph and you are standing on the treadmill
holding the plane, when the treadmill reaches 25 mph the plane will fly if
you let go of the plane.

If the engine on the plane is set to the proper power it will continue to
fly right beside you.


How is that possible if the wings are stationary? Are you saying the thing
will take off due to the pure power setting to keep up at 25mph (or
whatever), nothing to do with the wings?

---------------------------------
DW

So lets say I know my little RC plane takes off at exactly 25mph. So I crank
up the treadmill to step up to 25mph so I can keep the RC plane up on the
treadmill, the plane is completely stationary in regards to anyone standing
next to the plane but when the treadmill hits 25mph and my little RC plane
is staying even with the treadmill you are telling me I can pull back on the
elevator stick and the plane will take off? I don't think so.

Ok, now you've changed the problem. The way you state it here, your RC
plane will not take off, because it has no airspeed. However, in =your=
case, the treadmill speed is the independent condition, and the pilot is
adjusting his throttle to compensate. The pilot is ensuring that
airspeed is zero (assuming no wind). It will require about as much
power as it does to taxi, because all he's doing is overcoming wheel
friction.

There will be excess power available to the pilot, which he could use to
move forward faster than the treadmill is moving backwards, acquiring
airspeed and thus taking off. (but the pilot won't do that due to the
constraints of your problem, which says he won't do that).

In the =original= problem, the =pilot= is the independent variable. He
can do what he wants, and it's the treadmill that is tasked with
"keeping up" (whatever that means). Let's consider the following three
cases:

1: The treadmill is frictionless. In this case, we can ignore it. The
problem is the same as taking off from a maglev rail. The plane's
engines will push against the air, the plane will move forward, whatever
the treadmill does will not affect the forward motion of the airplane,
and the airplane will take off.

2: The treadmill and the plane's wheels are very sticky. The plane's
engines will push against the air, the plane will attempt to move
forward, pulling the treadmill bed with it. IF this is permitted, the
plane will gain airspeed and will take off, perhaps with the treadmill
dangling below its wheels. This may be a problem on landing. If the
treadmill bed is -not- permitted to move, then (by hypothesis) the
plane, being glued thereto, will not move. It's a static test stand,
not an airplane. But in that case all the king's horses couldn't move
the plane either.

5: The test is announced on usenet first. Everybody comes out to see
the test stand, and the resulting bluster of hot air allows the airplane
to easily reach a high enough airspeed even while standing still. The
airplane takes off before the test is even begun.

Jose
--
"There are 3 secrets to the perfect landing. Unfortunately, nobody knows
what they are." - (mike).
for Email, make the obvious change in the address.

Ray wrote:
Looks like airplane treadmill problem, regularly a spark for flame wars
on R.A.P., has made it into the mainstream.

http://pogue.blogs.nytimes.com/

http://www.straightdope.com/columns/060203.html

I really think I am right the plane
will not take off. The type of propulsion
is irrelevant.

Here's a similar problem. You, personally, are standing on a long
treadmill. You are holding a rope which is attached to the wall in
front of the treadmill. The treadmill is set up so that when you walk
(forwards), the treadmill bed moves (backwards) at an approprate speed
to keep you on the treadmill. This is equivalent to trying to walk on a
frictionless surface.

If you walk forwards, can you walk off the treadmill? (no)

If you pull on the rope, can you pull yourself off the treadmill? (yes)

If this were a real treadmill, would you have any issues? (yes, as you
pull yourself using the rope, the treadmill will spin backwards faster
and faster until you fall down, but you are still holding on to the
rope. You can still go hand over hand and move forward, while the
treadmill grinds through your clothing and racks up medical bills.

Jose
--
"There are 3 secrets to the perfect landing. Unfortunately, nobody knows
what they are." - (mike).
for Email, make the obvious change in the address.