A question I'm embarrased to ask - earth's spin

Jose wrote:
Orbital mechanis =is= "plain physics".

What makes orbital mechanics complicated is not that it isn't plain
physics, but that it isn't plane physics :-)

What makes orbital mechanics complicated is not that it isn't plain
physics, but that it isn't plane physics :-)

It is if your plane moves fast enough.

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.

Thanks to all who answered!

"xerj" wrote in message
...
I was talking about Coriolis effect with someone and he asked me about
planes against or with the earth's spin of around 1000mph at the equator.
He asked why this didn't benefit east to west plane travel timewise and
hurt west to east. I couldn't give him a straight answer, and felt like an
idiot when I said "it just doesn't".

What IS the straight answer? The dropping something in a moving vehicle
analogy doesn't work, does it? A plane has a method of acceleration,
whereas a passively dropped object doesn't.

Sometimes really simple questions can give you the worst time.

T o d d P a t t i s t wrote:
However, the original question was
about whether the Coriolis effect would "benefit east to
west plane travel timewise and hurt west to east"

Actually, that wasn't the original question, which is what I was
alluding to when I said "Xerj was confused." Xerj's friend simply asked
how come flying against the earth's spin isn't faster than flying with
the earth's spin? This is straight up an inertia question.
Unfortunately, the question proceeded a discussion on Coriolis effect,
making it sound like it was related to Coriolis effect.

Jose wrote:

taken to an orbital limit the object becomes weightless,

An object in orbit is not weightless. That's why it's held in orbit, by
gravity. If it was weightless, gravity could not act on it. It would not
have inertia. An object in orbit is actually in a constant state of
freefall. That's why you feel weightless, and things float about, when
in orbit.

Or when you make an airplane out of an orange crate and jump off the
garage roof. Nevermind....

John

If it was weightless, gravity could not act on it.

"If it were..." (not "if it was..."). Don't confuse weightless with
massless. Mass is the quantity that is conserved, and gives inertia.
Weight is the =force= due to gravity on that object. In a free falling
frame, an object is weighless, despite its mass.

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.

On Wed, 06 Dec 2006 19:51:46 -0800, Richard Riley
wrote:

On Tue, 05 Dec 2006 07:48:41 -0800, Ron Wanttaja
wrote:


Boeing launches from the equator.

http://www.boeing.com/special/sea-launch/

And Ariane launches from close to the equator
http://www.arianespace.com/site/spac...sub_index.html

The US uses
launch sites in California and Alaska for these types of launches.

I didn't know we launch from Alaska. I mean, except for the GMD
stuff. Huh.

They put an Athena into LEO from the Kodiak Launch Complex a few years back.

http://www.astronautix.com/sites/kodiak.htm

And, of course, are eager for more business.

http://www.akaerospace.com/facilities.html

They've hosted events like small satellite conferences; I visited a couple of
years back. VERY slick setup. It's amazing to visit a space launch center
where EVERYTHING is brand new. And where they've got free-range bison in the
launch control center parking lot....

http://www.wanttaja.com/ron&bison.jpg

Ah, well. Gators at Cape Canaveral, Californians in Vandenberg. :-)


Ron Wanttaja

Jose wrote:

"If it were..." (not "if it was...")

You're kidding, right?

Don't confuse weightless with
Mass is the quantity that is conserved,
I wasn't. I didn't know masses changed. By saying "conserved" are you
saying some went away. Do you mean 'constant'?





Weight is the =force= due to gravity on that object. In a free falling
frame, an object is weighless, despite its mass.



If it doesn't weigh anything, why is it falling?

Does it expierience microgravity?

"If it were..." (not "if it was...")

You're kidding, right?

Nope. "Were" is used with a subjunctive ("contrary to fact") condition.
"The sky isn't blue, but if it were, I could fly today."

I didn't know masses changed.

Except for nuclear reactions and high speeds, they don't. "Conserved"
(in physics) refers to a quantity the same before and after. For
example, a point can change how far north it is from another point
simply by changing the reference frame (magnetic, true), but the
distance is conserved.

In the statement I made about mass, "constant" works just as well, but
"conserved" is more to the point, as we are changing reference frame.

If it doesn't weigh anything, why is it falling?

It isn't. It's remaining right where it is. Only in the earth's
reference frame is it falling (accelerating downwards). But the earth's
frame is not the free-falling one I was talking about. In the reference
frame of the falling object, nothing at all is happening to it. It's
staying right where it is. ("Where are you?" "I'm right here. I'm
always 'right here', why do you keep asking!")

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.

On 5 Dec 2006 10:49:02 -0600, T o d d P a t t i s t
wrote:

Ron Wanttaja wrote:

Airplanes fly relative to the atmosphere. Since the atmosphere moves with the
Earth's spin, aircraft see no advantage from eastward flight.

Airplanes fly relative to whatever frame of reference you
want to use. If you use the spinning earth as a frame of
reference, then any motion in that frame produces
centrifugal or Coriolis force. Those forces affect the
amount of lift the plane must produce (unless they are
entirely horizontal.) The amount of lift affects the amount
of drag, and that affects fuel consumption. For relatively
low speeds, the effect on fuel consumption is tiny, but it
is measurable.

two comments on your posts

centrifugal force does not exist. it is an engineering misconception.
the force involved is inertia.

aeroplanes fly relative to the atmosphere they fly in.
mathematical abstractions are based on frames of reference.
the two are not the same.
wantajja's post was correct.
Stealth Pilot