Can a Plane on a Treadmill Take Off?

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
yearsg) 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.