Why airplanes taxi

wrote in message
...
Fixed-wing aircraft taxi because their wheels reduce friction as they
move forward
on the ground.

:-) I am feeling profound today...


How do they get a cab?

Tom C

On Feb 7, 6:00*am, Mxsmanic wrote:
writes:
And to answer your next post before you post it:

What molecules?

http://en.wikipedia.org/wiki/Outer_space

"While not being an actual perfect vacuum, outer space contains such sparse
matter that it can be effectively thought of as one. The pressure of
interstellar space is on the order of 10 pPa (1×10-11 Pa)."

So, no molecules. *And no friction.

Even if you don't wish to consider the hard vacuum of space as perfect, with a
pressure that is 10,000,000,000,000,000 times lower than that of Earth at sea
level, the friction should be also that much lower, and thus the speed of a
taxi should be trillions of times faster. *The speed of light is only fifteen
million times faster than a 40-knot taxi, so nearly the speed of light might
well be achieved long before any residual friction could have any effect.

The resistance is a function of the density of gas molecules not
pressure
density is related to pressure by
D=PM/RT
M=molecular wt
P=pressure
R=gas constant
T=temperature ( absolute )
ie the lower the temperature the higher the density
so what is the temperature in interestella space?

Resistance is also a function of the velocity squared.
think about how bit a number is c sqaured.

Terry
PPL Downunder

"Mxsmanic" wrote :

Fixed-wing aircraft taxi because their wheels reduce friction as they
move forward on the ground.

So, logically, spacecraft in the frictionless environment of outer space
should immediately accelerate to the speed of light.

The corollary to that would logically be that any object entering the
atmosphere from outer space would instantly decelerate to zero speed.

From this logically follows that any meteorites that succeed through the
atmosphere and hit Earth have an initial velocity faster than the speed of
light.

I think the meaning of logic got slighty warped as Mx's spacecraft passed
the most recent black hole. ;-)

On Feb 6, 11:51*am, Mxsmanic wrote:
writes:
Molecules

There aren't any molecules in space. *It's a hard vacuum.

A hard vacuum has lots of molecules. If you start going very fast,
they are going to hit you pretty hard. There is no such thing as
truly empty space...

On Feb 6, 12:02*pm, Mxsmanic wrote:
Robert M. Gary writes:
On Feb 6, 9:24*am, Mxsmanic wrote:
writes:
Fixed-wing aircraft taxi because their wheels reduce friction as they
move forward on the ground.

So, logically, spacecraft in the frictionless environment of outer space
should immediately accelerate to the speed of light.

No, it still takes energy to accelerate a mass, even in a frictionless
environment.

But the original post said that aircraft taxi because their wheels reduce
friction. *No mention of energy or force. *So if the statement is true,
movement results from a lack of friction alone, so zero friction should
produce infinite speed (or lightspeed if one allows the speed of light as an
absolute upper limit).

However, space (especially near space) is not frictionless.

Nor does friction produce acceleration. *QED.

Your post about airplanes flying stated that it was because of the
wings, no mention of energy or force, moron!

wrote in news:f5468d8b-0d97-452a-babc-
:

There is no such thing as truly empty space...

Sure there is. It is located between Mxsmanic's ears.

Tina writes:

Gee, where would the energy come from to cause the acceleration?

Exactly.

terry writes:

The resistance is a function of the density of gas molecules not
pressure
density is related to pressure by
D=PM/RT
M=molecular wt
P=pressure
R=gas constant
T=temperature ( absolute )
ie the lower the temperature the higher the density
so what is the temperature in interestella space?

The classic gas laws only work when a volume of gas is contained.

On Feb 6, 2:22*pm, Benjamin Dover wrote:
wrote in news:f5468d8b-0d97-452a-babc-
:

*There is no such thing as truly empty space...

Sure there is. *It is located between Mxsmanic's ears.

I stand corrected...

writes:

Your post about airplanes flying stated that it was because of the
wings, no mention of energy or force, moron!

What does that have to do with taxiing?