In article <1145114433.579713.201380@e56g2000cwe.googlegroups.com>,

In article <1145024825.891306.50680@i39g2000cwa.googlegroups.com>, "Randy Poe" <poespam-trap@yahoo.com> writes:

Mike wrote:

Martin Hogbin wrote:
So you and Randy agree the Coriolis effect is real. I suppose the same
holds for the centrifugal effect. So now let us take it from here.

Yes, they're real effects of conservation of momentum in
accelerated frames of reference.

Calling these forces "ficticious" must be justified in the context of
what ficticious means and not in some other context, like for instance
a posteriori derivation from a certain model.

It means they are not truly forces but artifacts of a coordinate
transformation. There isn't really an acceleration corresponding
to these "forces".

Careful here. Relative to the accelerating reference frame, where
you've these forces, there most certainly is an acceleration
corresponding to said forces.

My argument is similar to that brought up by Newton. These forces are
real. The fact that we cannot explain how they arise in non-inertial
reference frames does not immediately justify calling them ficticious.

We know precisely how they arise, that's how we can derive
equations for them. If I am driving in a straight line but
you are in a circle, you will conclude a "force" is making me
"curve". I can tell you precisely where that illusion is coming
from and calculate the precise amount.

It is not an illusion. Repeat, *it is not an ilusion*. It is a
perfectly real effect resulting from a specific choice of a reference
frame.

Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"

I'm trying to follow your discussion with great interest. As a graduate
PhilSci student long time ago, my thesis dealt with the subject of
force. Some of you might not know that there were a few alternatives to
the Newtonian definition of force, before and after Newton. One such
definition was offered by Leibniz, equating (active) force to mv^2 and
(passive) force to mv. Newton's definition survived because it fitted
well with his law of gravitation.

No, not only because of this. It fits well with everything else as
well.

Now, in a peper published last year in a second class rated journal --
this does not bother me at all -- another definition of force was
presented. Basically, that force is equal to the rate of change of
kinetic energy, also known as instantenuous power. I found this highly
interesting since defining force in such a way makes it a scalar
quantity.

And why this should be a plus? We know that same interaction but
acting in different directions will result in different motions.
Unless, of course, you consider all motions with same kinetic energy
the same. But then you've just lost lots of information.

In the paper I mentioned there is also a reference to the problem of
ficticious forces and how this new definition of force -- I call it new
because I have not seen it before -- makes the corresponding laws of
motion -- also presented in the paper -- form invariant in all frames
of reference, inertial or non-inertial, for freely moving particles or
particles in uniform motion, linear or curvilinear.

Sounds a big claim. Will have to see it to believe. Anyway, two
things worth mentioning:

1) There is no "problem of ficticious forces". The only problems
here are semantic.

2) While the notion of force was fundamental in the early formulation
of mechanics, currently it is rather secondary.

This is a straight

forward result but neverthless very interesting. You can find the
paper at the following web link:

http://www.doaj.org/abstract?id=119444&toc=y/


Joe Avery

Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"

In article <1145114433.579713.201380@e56g2000cwe.googlegroups.com>,

In article <1145024825.891306.50680@i39g2000cwa.googlegroups.com>, "Randy Poe" <poespam-trap@yahoo.com> writes:

Mike wrote:

Martin Hogbin wrote:
So you and Randy agree the Coriolis effect is real. I suppose the same
holds for the centrifugal effect. So now let us take it from here.

Yes, they're real effects of conservation of momentum in
accelerated frames of reference.

Calling these forces "ficticious" must be justified in the context of
what ficticious means and not in some other context, like for instance
a posteriori derivation from a certain model.

It means they are not truly forces but artifacts of a coordinate
transformation. There isn't really an acceleration corresponding
to these "forces".

Careful here. Relative to the accelerating reference frame, where
you've these forces, there most certainly is an acceleration
corresponding to said forces.

My argument is similar to that brought up by Newton. These forces are
real. The fact that we cannot explain how they arise in non-inertial
reference frames does not immediately justify calling them ficticious.

We know precisely how they arise, that's how we can derive
equations for them. If I am driving in a straight line but
you are in a circle, you will conclude a "force" is making me
"curve". I can tell you precisely where that illusion is coming
from and calculate the precise amount.

It is not an illusion. Repeat, *it is not an ilusion*. It is a
perfectly real effect resulting from a specific choice of a reference
frame.

Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"

I'm trying to follow your discussion with great interest. As a graduate
PhilSci student long time ago, my thesis dealt with the subject of
force. Some of you might not know that there were a few alternatives to
the Newtonian definition of force, before and after Newton. One such
definition was offered by Leibniz, equating (active) force to mv^2 and
(passive) force to mv. Newton's definition survived because it fitted
well with his law of gravitation.

No, not only because of this. It fits well with everything else as
well.

Now, in a peper published last year in a second class rated journal --
this does not bother me at all -- another definition of force was
presented. Basically, that force is equal to the rate of change of
kinetic energy, also known as instantenuous power. I found this highly
interesting since defining force in such a way makes it a scalar
quantity.

And why this should be a plus? We know that same interaction but
acting in different directions will result in different motions.
Unless, of course, you consider all motions with same kinetic energy
the same. But then you've just lost lots of information.

In the paper I mentioned there is also a reference to the problem of
ficticious forces and how this new definition of force -- I call it new
because I have not seen it before -- makes the corresponding laws of
motion -- also presented in the paper -- form invariant in all frames
of reference, inertial or non-inertial, for freely moving particles or
particles in uniform motion, linear or curvilinear.

Sounds a big claim. Will have to see it to believe. Anyway, two
things worth mentioning:

1) There is no "problem of ficticious forces". The only problems
here are semantic.

2) While the notion of force was fundamental in the early formulation
of mechanics, currently it is rather secondary.

This is a straight

forward result but neverthless very interesting. You can find the
paper at the following web link:

http://www.doaj.org/abstract?id=119444&toc=y/


Joe Avery

Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"

mmeron@cars3.uchicago.edu wrote:

In article <1145114433.579713.201380@e56g2000cwe.googlegroups.com>,

mmeron@cars3.uchicago.edu wrote:

In article <1145024825.891306.50680@i39g2000cwa.googlegroups.com>, "Randy Poe" <poespam-trap@yahoo.com> writes:

Mike wrote:

Martin Hogbin wrote:
So you and Randy agree the Coriolis effect is real. I suppose the same
holds for the centrifugal effect. So now let us take it from here.

Yes, they're real effects of conservation of momentum in
accelerated frames of reference.

Calling these forces "ficticious" must be justified in the context of
what ficticious means and not in some other context, like for instance
a posteriori derivation from a certain model.

It means they are not truly forces but artifacts of a coordinate
transformation. There isn't really an acceleration corresponding
to these "forces".

Careful here. Relative to the accelerating reference frame, where
you've these forces, there most certainly is an acceleration
corresponding to said forces.

My argument is similar to that brought up by Newton. These forces are
real. The fact that we cannot explain how they arise in non-inertial
reference frames does not immediately justify calling them ficticious.

We know precisely how they arise, that's how we can derive
equations for them. If I am driving in a straight line but
you are in a circle, you will conclude a "force" is making me
"curve". I can tell you precisely where that illusion is coming
from and calculate the precise amount.

It is not an illusion. Repeat, *it is not an ilusion*. It is a
perfectly real effect resulting from a specific choice of a reference
frame.

Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"

I'm trying to follow your discussion with great interest. As a graduate
PhilSci student long time ago, my thesis dealt with the subject of
force. Some of you might not know that there were a few alternatives to
the Newtonian definition of force, before and after Newton. One such
definition was offered by Leibniz, equating (active) force to mv^2 and
(passive) force to mv. Newton's definition survived because it fitted
well with his law of gravitation.

No, not only because of this. It fits well with everything else as
well.

Now, in a peper published last year in a second class rated journal --
this does not bother me at all -- another definition of force was
presented. Basically, that force is equal to the rate of change of
kinetic energy, also known as instantenuous power. I found this highly
interesting since defining force in such a way makes it a scalar
quantity.

And why this should be a plus? We know that same interaction but
acting in different directions will result in different motions.
Unless, of course, you consider all motions with same kinetic energy
the same. But then you've just lost lots of information.

Not KE but rate of change of KE. This carries force information, which
in turn has the direction, etc. as in d(KE)/dt = dp/dt o v

Now, this scalar is zero when the two vectors -- dp/dt & v -- are
orthogonal. In frames of reference attached to rotating bodies the rate
is zero because the velocity v is equal to zero in those frames.

Therefore, in both frames, inertial and non-inertial, the quantity that
is (hypothetically) causing rotational motion is equal to zero. Strange
but this law of motion that was presented in the paper I mentioned --
as compared to F = dp/dt -- needs no adjustements regardless of the
type of reference frame it is used with (inertial or non-inertial).

It looks like a very simple and elegant result and either everybody
overlooked it or there is a catch I cannot see.

In the paper I mentioned there is also a reference to the problem of
ficticious forces and how this new definition of force -- I call it new
because I have not seen it before -- makes the corresponding laws of
motion -- also presented in the paper -- form invariant in all frames
of reference, inertial or non-inertial, for freely moving particles or
particles in uniform motion, linear or curvilinear.

Sounds a big claim. Will have to see it to believe. Anyway, two
things worth mentioning:

1) There is no "problem of ficticious forces". The only problems
here are semantic.

I agree after reading what some people have to say about this -- PD and
Roberts mainly. As it turns out, centrifugal forces do not really
exist. The measured acceleration is due to "inertial" effects. This
means the cause of these effects is the inertia of the body in motion.
When you set a body in rotation, the centripetal force acts towards the
center of motion. Inertia tries to take the body on a straight path.
The combination of these two motions is a rotation. Without the
inertial effect, rotation would be impossible.

I think any use of the term 'centrifugal forces' is an unfortunate
choice of early formulations of Mechanics and some people are still
stuck with it.

If I recall corectly, Landau used "inertial" forces instead.

2) While the notion of force was fundamental in the early formulation
of mechanics, currently it is rather secondary.

Technically this depends on the system of units used.

Philosophically
speaking, the notion of force and specifically the use of force in
modeling gravity is now history after General Relativity and other
geometrical models of spacetime and Lagrangian interaction.