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

"peter" wrote in message
oups.com...
The problem is that as it is stated, the scenario is not one that could
ever be created with a real treadmill subject to normal engineering
constraints. [...]

You can interpret the question in that way of course. However, the intent
of the "puzzler" is clear, and the fact that it is poorly stated should not
interfere with making a reasonable, good faith effort to address the
intended question.

It's well and good to nitpick about physically impossible situations, but
rest assured if you started doing so in a true interactive situation in
which the person stating the puzzle had the opportunity to restate it, you
would quickly get past the nitpicking and get to the intended question.

It's a waste of time to do the nitpicking in the first place. It's easy
enough to infer what the interesting question really is. And the
interesting question doesn't have the treadmill blowing up.

Pete

Peter Duniho wrote:
"peter" wrote in message
oups.com...
The problem is that as it is stated, the scenario is not one that could
ever be created with a real treadmill subject to normal engineering
constraints. [...]

You can interpret the question in that way of course. However, the intent
of the "puzzler" is clear, and the fact that it is poorly stated should not
interfere with making a reasonable, good faith effort to address the
intended question.

It's well and good to nitpick about physically impossible situations, but
rest assured if you started doing so in a true interactive situation in
which the person stating the puzzle had the opportunity to restate it, you
would quickly get past the nitpicking and get to the intended question.

It's a waste of time to do the nitpicking in the first place. It's easy
enough to infer what the interesting question really is.

My view was that it was exactly the infinite feedback mechanism that
made the problem as stated interesting. Otherwise it's trivial and
boring.

On Mon, 11 Dec 2006 21:10:32 -0800, peter wrote
(in article om):

Peter Duniho wrote:
"peter" wrote in message
oups.com...
The problem is that as it is stated, the scenario is not one that could
ever be created with a real treadmill subject to normal engineering
constraints. [...]

You can interpret the question in that way of course. However, the intent
of the "puzzler" is clear, and the fact that it is poorly stated should not
interfere with making a reasonable, good faith effort to address the
intended question.

It's well and good to nitpick about physically impossible situations, but
rest assured if you started doing so in a true interactive situation in
which the person stating the puzzle had the opportunity to restate it, you
would quickly get past the nitpicking and get to the intended question.

It's a waste of time to do the nitpicking in the first place. It's easy
enough to infer what the interesting question really is.

My view was that it was exactly the infinite feedback mechanism that
made the problem as stated interesting. Otherwise it's trivial and
boring.


Heh, heh. So use a ski plane. Since the speed of the skis is "zero" under the
terms of the problem, the treadmill will remain motionless! Problem solved.

Actually the question makes sense, at least to the non-aviation public,
because the normal use of a treadmill suggests the opposite, ie a
person walking on the treadmill remains stationary, yet he burns energy
as if he were walking on solid ground. The same would be true if it
were a car, except it would burn slightly less fuel because of the lack
of wind resistance (same is true for a person walking too, but the wind
resistance is even more negligible for walking).

A better way to pose the airplane question would be " what would
happen if the airplane is landing on a treadmill that is moving in the
opposite direction and speed?"






Peter Duniho wrote:
"Ray" wrote in message
...
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/

And handled with every bit as much intelligence and consideration as we've
seen here. Which is to say, there's no shortage of people convinced that
the airplane won't take off, even though it will.

Let the arguing begin!

Why? Haven't you had enough by now?

A better way to pose the airplane question would be " what would
happen if the airplane is landing on a treadmill that is moving in the
opposite direction and speed?"

How about dispensing with the treadmill entirely. What would happen if
the airplane were on a frictionless surface? The wheels couldn't push
on anything, so how would the airplane take off?

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.

"Jose" wrote in message
...
A better way to pose the airplane question would be " what would
happen if the airplane is landing on a treadmill that is moving in the
opposite direction and speed?"

How about dispensing with the treadmill entirely. What would happen if
the airplane were on a frictionless surface? The wheels couldn't push on
anything, so how would the airplane take off?

Jose

???

The wheels don't have to push on anything for an aircraft to take
off...there's no drivetrain feeding power to the wheels!

Jay B

The wheels don't have to push on anything for an aircraft to take
off...there's no drivetrain feeding power to the wheels!

Right. Phrasing it the way I did may get people to realize this, or at
least to think about it themselves.

If you put an airplane on the roof of a speeding train, would it take
off? What if the train were shaped like a runway? What if it were very
thin?

They are all ultimately the same question.

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.

"Andrew Sarangan" wrote in message
ps.com...
Actually the question makes sense, at least to the non-aviation public,
because the normal use of a treadmill suggests the opposite, ie a
person walking on the treadmill remains stationary, yet he burns energy
as if he were walking on solid ground.

Who says the question doesn't make sense?

The problem that the people who don't "get it" have is that a typical
treadmill is used in a situation where propulsion is via the interface with
the ground, whereas airplanes get their propulsion via other means. (And I
don't think this has anything to do with aviation public vs non-aviation
public...plenty of pilots don't understand the physics either, as has been
amply demonstrated here).

[...]
A better way to pose the airplane question would be " what would
happen if the airplane is landing on a treadmill that is moving in the
opposite direction and speed?"

That's not a better way at all. That asks an entirely different question
and takes advantage of a completely different prejudice the answerer might
have.

Pete

"Ray" wrote in message ...
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/

Let the arguing begin!

- Ray

That would depend on what has the greater resistance,
the air in front of the plane or the belt on the treadmill.
If it was harder for the plane to push through the air in
front of it then the plane would merely roll stationary
on the treadmill.
If the resistance of the treadmill rollers was greater
than the air in front of the plane then the plane would
push forward thereby achieving lift through air flow
passage over the wings.

You can equate it to an airboat in a river.
Will the river push the airboat down stream or
will the propulsion of the engine move it forward?

Just my two cents worth....

David
Greer, SC

"FLAV8R" wrote in message
...
That would depend on what has the greater resistance,
the air in front of the plane or the belt on the treadmill.

No, it would not depend on that at all. Both of those effects are creating
a resistance in the same direction, and thus are additive. Which one is
greater is irrelevant. The only relevant question is whether they combined
exceed the thrust from the engines.

They don't even come close to doing that, and so the engines can easily push
the airplane forward to a high enough speed for flight.

[...]
You can equate it to an airboat in a river.
Will the river push the airboat down stream or
will the propulsion of the engine move it forward?

It's similar, yes. Except that the drag due to friction from the treadmill
is miniscule, whereas hydrodynamic drag is significant.

Pete