("Tony" wrote)
> An aircraft would need no additional power to accelerate to 60 on a
> treadmill.


Yeah, well I just set that sucker to...."Incline Setting # 12"

If you set your comms to the frequency, posted up there under that TV in
front of you, you'll be able to listen to Oprah.


Montblack

Jim wrote:
>If the brtakes
>were set, the treadmill would roll and the airplane would
>likely come to a stop when it departed the treadmill unless
>it was alrady at flying speed.

Reminds me of a joke, How does a navy pilot know if his LG are up?
When it takes full power to taxi <g>

The Monk

Tony wrote:

> cjcampbell wrote
>
> If the car's airspeed indicator said 60 then the speedometer will
> indicate 120. But the car would then need to expend the same energy to
> accelerate to 60 as it would to accelerate to 120 on a stationary road.

Wrong. The energy required to spin the wheels at 120 MPH isn't at all
the same as that required to accelerate the entire car to 120 MPH.


Matt

On the contrary, the problem clearly states that the conveyor is moving at
the speed that the plane is moving (but in the opposite direction). If the
plane is not moving, the conveyor would not be moving. If the conveyor is
moving, the plane MUST be moving. If it's moving fast enough, it will take
off.

--
Bob (Chief Pilot, White Knuckle Airways)


"Thomas Borchert" > wrote in message
...
> Greg,
>
>> If you have a motoroized conveyor which
>> always reduces the plane's forward movement to zero,
>>
>
> Nowhere does it say that in the question.
>
> --
> Thomas Borchert (EDDH)
>

Alex wrote:
>Totally irrelevant. The answer is the same for a glider being towed to
>take-off by a ground vehicle (except that you would want to change the
>rear end or wheel size of the vehicle to cut the final drive ratio in
>half, so that it could attain the doubled wheel speed necessary to
>attain the needed forward speed.)

Just as the propellor on a plane is independent of the treadmill, the
tow car in your scenario must also be independent of the treadmill, ie.
running along side on solid ground while the glider is on the
treadmill. Co-Peach? (That's my Italian LOL)

The Monk

We don't have enough information. What color is the airplane? What
ratings does the pilot have? How many postings will this thread have
before it dies?

Tony wrote:

> We don't have enough information. What color is the airplane? What
> ratings does the pilot have? How many postings will this thread have
> before it dies?
>

This thread sure beats all of the one's posted lately on plane crashes.
I'd much rather contemplate this than hear gory details about another
crash. I just don't understand folks who get their jollies posting that
stuff.


Matt

"Bob Chilcoat" > wrote in message
...
> On the contrary, the problem clearly states that the conveyor is moving at
> the speed that the plane is moving (but in the opposite direction).

The statement "the conveyor is moving at the speed that the plane is moving"
(the one you say the problem states) is a very different statement from
"which always reduces the plane's forward movement to zero" (the statement
Thomas responded to).

How is your post contrary to Thomas'?

Pete

"Flyingmonk" > wrote:

>Alex wrote:
>>Totally irrelevant. The answer is the same for a glider being towed to
>>take-off by a ground vehicle (except that you would want to change the
>>rear end or wheel size of the vehicle to cut the final drive ratio in
>>half, so that it could attain the doubled wheel speed necessary to
>>attain the needed forward speed.)
>
>Just as the propellor on a plane is independent of the treadmill, the
>tow car in your scenario must also be independent of the treadmill, ie.
>running along side on solid ground while the glider is on the
>treadmill. Co-Peach? (That's my Italian LOL)
>
>The Monk

That's a possibility, but I was assuming a tow car ONE the conveyor.
So even with the drive wheels on the conveyor, it can still take off.
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

sure, in our imaginary world. in the real world nobody will
try this so mechanical limitations are unimportant.


"alexy" > wrote in message
...
| "Jim Macklin" >
wrote:
|
|
| >b. If the treadmill was powered [and everything was
timed
| >in sync] the belt would be accelerating rearward and the
| >engine thrust would be pulling forward at the same rate,
| >thus the airframe mounted wigs would have near zero
airspeed
| >and lift and would not fly.
|
| Just to "set the hook" here, are you saying that it will
be possible
| to have the conveyer move backwards fast enough that the
plane remains
| still, even under full power, and with no brakes on?
| --
| Alex -- Replace "nospam" with "mail" to reply by email.
Checked infrequently.

Not true. The original problem statement was this:

"An airplane on a runway sits on a conveyer belt that moves in the
opposite direction at exactly the speed that the airplane is moving
forward. Does the airplane take off?" (Assuming the tires hold out, of
course.)

I restated it, but either version clearly implies that the airplane must be
moving for the conveyor to be moving. Sure if the plane isn't moving, it
won't take off. But if the conveyor is moving, the plane must be moving in
the opposite direction, because that's what the problem says. The problem
never said that the conveyor somehow moves in a way that cancels the plane's
forward motion.

As many have stated, unless the pilot is applying the brakes, so that there
is friction between the wheels and the belt, the movement of the conveyor
has nothing to do with the speed of the plane. All the problem says is that
the conveyor is moving in the opposite direction at the same speed as the
plane.
--
Bob (Chief Pilot, White Knuckle Airways)


"Peter Duniho" > wrote in message
...
> "Bob Chilcoat" > wrote in message
> ...
>> On the contrary, the problem clearly states that the conveyor is moving
>> at the speed that the plane is moving (but in the opposite direction).
>
> The statement "the conveyor is moving at the speed that the plane is
> moving" (the one you say the problem states) is a very different statement
> from "which always reduces the plane's forward movement to zero" (the
> statement Thomas responded to).
>
> How is your post contrary to Thomas'?
>
> Pete
>

My post is not contrary to Thomas', it reinforces his comment. My statement
is a further rebuttal to the statement thomas was responding to.

--
Bob (Chief Pilot, White Knuckle Airways)


"Peter Duniho" > wrote in message
...
> "Bob Chilcoat" > wrote in message
> ...
>> On the contrary, the problem clearly states that the conveyor is moving
>> at the speed that the plane is moving (but in the opposite direction).
>
> The statement "the conveyor is moving at the speed that the plane is
> moving" (the one you say the problem states) is a very different statement
> from "which always reduces the plane's forward movement to zero" (the
> statement Thomas responded to).
>
> How is your post contrary to Thomas'?
>
> Pete
>

"Tony" > wrote in message
oups.com...
> We don't have enough information. What color is the airplane? What
> ratings does the pilot have? How many postings will this thread have
> before it dies?

Also need more information on the treadmill.

Is this the same type of treadmill that a guy named George walks his dog on,
a cat jumps onto the treadmill and the dog starts chasing it causing the
treadmill to speed up. George falls down on the treadmill but isn't thrown
off...

Hence, if George can't get off the treadmill, how can a plane???

"Jim Macklin" > wrote:
>"alexy" > wrote in message
...
>| "Jim Macklin" >
>wrote:
>|
>|
>| >b. If the treadmill was powered [and everything was
>timed
>| >in sync] the belt would be accelerating rearward and the
>| >engine thrust would be pulling forward at the same rate,
>| >thus the airframe mounted wigs would have near zero
>airspeed
>| >and lift and would not fly.
>|
>| Just to "set the hook" here, are you saying that it will
>be possible
>| to have the conveyer move backwards fast enough that the
>plane remains
>| still, even under full power, and with no brakes on?

>
>sure, in our imaginary world. in the real world nobody will
>try this so mechanical limitations are unimportant.

Okay, if that happens (the treadmill moving fast enough backwards to
offset the thrust of the plane's propulsion system), how fast will the
plane be moving forward? ?

Given your answer to that, how fast will the conveyor be moving, given
that the conveyer moves backward at the same speed at which the plane
moves forward?

Given your answer to that, what's to stop the plane from moving
forward?

The problem says the conveyer moves at the same speed as the plane.
How in the world can it, by moving the same speed as the plane,
prevent the plane's motion?

One more thought: I'm getting ready to get an emissions test on my
car. They put the back wheels on rollers, put it in gear, and run the
engine up until the indicated speed is, e.g., 30mph. This seems to be
the situation that you and a few others picture happening here. But in
my case, my car is NOT moving forward, so I would NOT say that the
roller under my wheels was moving at the same speed as my car. It is
turning at the same rate as my car's wheels, which is a whole 'nother
kettle of fish.
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

"Bob Chilcoat" > wrote in message
...
> My post is not contrary to Thomas', it reinforces his comment. My
> statement is a further rebuttal to the statement thomas was responding to.

You made two replies to my own post, which are in contradiction with each
other.

Furthermore, if you intend to reinforce a person's post, I suggest you not
begin the post with the words "on the contrary".

Bob,

> On the contrary, the problem clearly states that the conveyor is moving at
> the speed that the plane is moving (but in the opposite direction).
>

Huh? The OP was saying "If you have a conveyoer which always reduces the
airplane's movement to zero", to which I said "the original question doesn't
say that". What does you statement have to do with what I said, let alone it
being "contrary"?

--
Thomas Borchert (EDDH)

Peter,

> Furthermore, if you intend to reinforce a person's post, I suggest you not
> begin the post with the words "on the contrary".
>

I didn't get it, either ;-)

--
Thomas Borchert (EDDH)

"Tony" > wrote in message
oups.com...
> We don't have enough information. What color is the airplane? What
> ratings does the pilot have? How many postings will this thread have
> before it dies?

Was there a flight plan filed?

Allen

Thomas Borchert > wrote:

>Peter,
>
>> Furthermore, if you intend to reinforce a person's post, I suggest you not
>> begin the post with the words "on the contrary".
>>
>
>I didn't get it, either ;-)

Easy, boys!

Bob, it took me a couple of readings initially to realize that what
you meant was "I agree with your comment, Thomas, and furthermore, to
the contrary of the post to which you were replying...". As Perter
says, when you start a post with "on the contrary" it sounds like you
are disagreeing with the post to which you were replying. Then it's
left to the reader to puzzle out whether you didn't understand the
post to which you were replying (and thought you were disagreeing when
in fact you were agreeing) or whether it was just a careless wording,
as I assumed.

But, semantics aside, it sounds like the four of us are solidly on the
side of a plane not just sitting stationary, spinning its wheels on a
conveyer!

--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

"Peter Duniho" > wrote:

>"alexy" > wrote in message
...
>> Just to "set the hook" here, are you saying that it will be possible
>> to have the conveyer move backwards fast enough that the plane remains
>> still, even under full power, and with no brakes on?
>
>I thought you had already established that it would be possible, and that
>the treadmill speed is "somewhat below the speed of light"? You didn't
>appear to solve the "materials integrity" aspect of the problem, but that
>seems like a minor quibble. :)

You know, there is a fallacy in my reasoning that I am surprised no
one has called me on. We are used to aerodynamic drag, which increases
as the square of velocity. But if my memory of high school physics is
correct (and if Newton hasn't changed his mind in the last 40
years<g>) the friction between two bodies is a coefficient of friction
times the force normal to the motion (i.e., the weight of the plane).
No component for the relative velocities of the two bodies! So the
drag due to wheels is small, and speeding up the conveyer will not
increase that small drag, at least until you get to the "noise"
elements that make the idealized drag model imperfect.

I guess that by _accelerating_ the conveyer, you could make the plane
use all of its power for a short while providing the angular
acceleration to the wheels, but you very quickly get to relativistic
speeds, without ever reaching a steady state tradeoff for the
engine/prop's thrust.

Much easier to just read the problem as stated, and have the conveyer
only move as fast backwards as the plane moves forward!!

--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

cjcampbell wrote:
> Saw this question on "The Straight Dope" and I thought it was amusing.
>
> http://www.straightdope.com/columns/060203.html
>
> The question goes like this:
>
> "An airplane on a runway sits on a conveyer belt that moves in the
> opposite direction at exactly the speed that the airplane is moving
> forward. Does the airplane take off?" (Assuming the tires hold out, of
> course.)
>
> Cecil Adams (world's smartest human being) says that it will take off
> normally.

The plane will take off because:

For example, a 1000ft conveyer belt lays on a runway.
The plane is placed on this conveyer belt.
Engine is started and full throttle applied.
The plane will move forward and the belt back at the same speed as the
plane.
After 1000ft the belt has moved back enough so the plane thumps on the
runway, starts its take-off roll and takes off.

-Kees

P.S. I'm not serious.

Is this an Eastbound airplane, or West?

Al


"Tony" > wrote in message
oups.com...
> We don't have enough information. What color is the airplane? What
> ratings does the pilot have? How many postings will this thread have
> before it dies?
>

"alexy" > wrote in message
...
> You know, there is a fallacy in my reasoning that I am surprised no
> one has called me on. We are used to aerodynamic drag, which increases
> as the square of velocity. But if my memory of high school physics is
> correct (and if Newton hasn't changed his mind in the last 40
> years<g>) the friction between two bodies is a coefficient of friction
> times the force normal to the motion (i.e., the weight of the plane).
> No component for the relative velocities of the two bodies!

Hardly seemed worth it, given the opportunity to equivocate on the point.
In particular, while the idealized friction drag remains static relative to
speed, that ignores the possibility for change in the materials as the
friction heats them. Expansion may create a higher normal force (depending
on what part expands faster), and thus higher frictional drag. It also
ignores aerodynamic drag around the surface of the tire.

While I haven't bothered to calculate what these increases would be, it
seems safe to say that it's *possible* they would rise fast enough to offset
the available thrust before reaching the speed of light.

Basically, in an arm-chair, lay-person discussion like this, practically
*anything* is possible as you approach the speed of light. So why not just
invoke that, and ignore the details? :)

Pete

Strap a big enough engine on the treadmill, and one way or another,
you'll make it take off.

("Peter Duniho" wrote)
> While I haven't bothered to calculate what these increases would be, it
> seems safe to say that it's *possible* they would rise fast enough to
> offset the available thrust before reaching the speed of light.
>
> Basically, in an arm-chair, lay-person discussion like this, practically
> *anything* is possible as you approach the speed of light. So why not
> just invoke that, and ignore the details? :)


Let's take this away from the light...

For the plane NOT to take off - the plane must have zero forward
movement/airspeed. According to the OP rules, in that state the belt is
stationary.

If the prop is pulling at the plane to go forward, the belt can keep up
(debate-debate-debate) causing the plane not to make any headway. Again,
in-that-state, the belt must (now) stop because it only travels backward at
the same speed as the plane moves forward - but the plane is still pulling
forward ...against a (now) stationary belt.

I'm (now) officially confused.


Montblack
http://www.artfinale.com/store/sku_pgs/E06BT.php
Taking steps to get the right answer.

Help, we're all on a treadmill and we can't get off.

What can we take for brain misfunction?

Whatever. I give up. You win, smartass. This is getting too far off
topic anyway. The question was, will the plane fly yes or no. The
answer is yes. Period. My vectorial explanation was a good start in
trying to explain this.
Happy flying!

"Montblack" > wrote in message
...
> Let's take this away from the light...
>
> For the plane NOT to take off - the plane must have zero forward
> movement/airspeed. According to the OP rules, in that state the belt is
> stationary. [...]

See, this is where you went wrong. This little tangent is not about the
original post's rules. The original problem has been modified for the
purpose of entertainment, not enlightenment.

Sorry for the confusion. Everyone seems to have figured out what I meant.
I was in a hurry to leave for Utah to ski, which is why I haven't replied
until now. I only just got back. Bottom line: The plane will take off
just fine, unless there is a LOT of friction in the wheel bearings.

--
Bob (Chief Pilot, White Knuckle Airways)


"alexy" > wrote in message
...
> Thomas Borchert > wrote:
>
>>Peter,
>>
>>> Furthermore, if you intend to reinforce a person's post, I suggest you
>>> not
>>> begin the post with the words "on the contrary".
>>>
>>
>>I didn't get it, either ;-)
>
> Easy, boys!
>
> Bob, it took me a couple of readings initially to realize that what
> you meant was "I agree with your comment, Thomas, and furthermore, to
> the contrary of the post to which you were replying...". As Perter
> says, when you start a post with "on the contrary" it sounds like you
> are disagreeing with the post to which you were replying. Then it's
> left to the reader to puzzle out whether you didn't understand the
> post to which you were replying (and thought you were disagreeing when
> in fact you were agreeing) or whether it was just a careless wording,
> as I assumed.
>
> But, semantics aside, it sounds like the four of us are solidly on the
> side of a plane not just sitting stationary, spinning its wheels on a
> conveyer!
>
> --
> Alex -- Replace "nospam" with "mail" to reply by email. Checked
> infrequently.

LOL Bob, I thought for sure this horse was definitely dead. Hahaha.

("T o d d P a t t i s t" wrote)
> But what I want to know is if the horse had wings, a la Pegasus, and was
> on a treadmill going the opposite direction, could the horse take off?


Depends. Is the carrot and stick secured to the horse or the treadmill?


Montblack

>Depends. Is the carrot and stick secured to the horse or the treadmill?

Dang it! This thing just wont die! :^)

The Monk

Thomas Borchert wrote:
> Bob,
>
> > On the contrary, the problem clearly states that the conveyor is moving at
> > the speed that the plane is moving (but in the opposite direction).
> >
>
> Huh? The OP was saying "If you have a conveyoer which always reduces the
> airplane's movement to zero", to which I said "the original question doesn't
> say that".

I did not say that, either. I said the conveyer was moving at the speed
the airplane is moving, but in the opposite direction. I did not say
that the conveyer reduced the airplane's movement to zero, an
impossibility short of tethering the airplane.

With respect to what?

I'm not responding to anything in specific, but to the mere fact that
this thread has gone on so long. You can answer all your questions by
answering "with respect to what?" for all movement issues, and realizing
that the airplane flies (or not) by moving with respect to the
surrounding air.

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.

On Thu, 16 Feb 2006 11:11:27 -0500, T o d d P a t t i s t
> wrote:

> "Flyingmonk" > wrote:
>
> >LOL Bob, I thought for sure this horse was definitely dead. Hahaha.
>
> But what I want to know is if the horse had wings, a la
> Pegasus, and was on a treadmill going the opposite
> direction, could the horse take off?

Depends on whether the horse needs forward motion through the air or not. It
it can take off from a standing position, then the answer is yes. If it
needs a running start, the answer is no.
Q.E.D.

("T o d d P a t t i s t" wrote)
> They're secured to Pegasus, but what I'm not going to specify is whether
> Pegasus uses the traction of his hooves against the ground or the beat of
> his wings against the air to gain flying speed.


Poor little hooves - spinning at twice the speed of the treadmill.

It hurts just thinking about it.


Montblack

"Montblack" > wrote in message
...
> ("T o d d P a t t i s t" wrote)
>> They're secured to Pegasus, but what I'm not going to specify is whether
>> Pegasus uses the traction of his hooves against the ground or the beat of
>> his wings against the air to gain flying speed.
>
>
> Poor little hooves - spinning at twice the speed of the treadmill.
>
> It hurts just thinking about it.
>
>
> Montblack

Could be a Harrier horse.