[time-nuts] FW: Pendulums & Atomic Clocks & Gravity

[Ulrich Bangert]

Didier,

my first posting to that topic contained the semtences:

> Centrifugal forces are so called fictitious forces 
> which are only observed from within accelerated systems. 
> Normal physics is done in inertial systems.

Is that not pretty much what you have found out after all?

73s and my best regards
Ulrich, DF6JB

> -----Ursprüngliche Nachricht-----
> Von: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Didier Juges
> Gesendet: Mittwoch, 30. Mai 2007 02:35
> An: Discussion of precise time and frequency measurement
> Betreff: Re: [time-nuts] FW: Pendulums & Atomic Clocks & Gravity
> 
> 
> James,
> 
> Where were you all week-end?
> 
> Your explanations are so clear, it makes sense now. Thank you 
> very much.
> 
> I understand now that centrifugal forces are necessary to 
> explain the behavior of objects when an accelerating frame of 
> reference is used, but not necessary (actually 
> counter-productive) to explain the behavior of the same 
> objects when an inertial frame of reference is used.
> 
> That solves my problem and the apparent contradiction that 
> sometimes the centrifugal force is necessary and sometimes 
> not, because I did not appreciate the effects of changing the 
> frame of reference.
> 
> Thanks a lot again.
> 
> I had no idea time-nuts would drive me to brush-up on physics :-)
> 
> Didier KO4BB
> 
> ---- James Maynard <james.h.maynard at usa.net> wrote: 
> 
> > The reason that the frame of reference matters is that gravity is
> > indistinguishable from acceleration. (This is an assumption that 
> > Einstein made when deriving his general theory of 
> relativity. It seems 
> > to work.)
> > 
> > An "inertial" frame of reference is a non-accelerating frame of
> > reference. In an inertial frame of reference, Newton's laws 
> of motion 
> > work -- if you use Newton's gravitational relationship, that the 
> > gravitational force (weight) that each of two bodies exerts 
> on the other 
> > is proportional to both their masses, and inversely 
> proportional to the 
> > square of the distance between them.
> > 
> > In an accelerating frame of reference (either linear 
> acceleration, or
> > rotational acceleration, or both) additional forces, 
> technically called 
> > "fictitious" forces, must be introduced in order to explain 
> the motions 
> > of bodies with Newtonian mechanics. The "fictitious" forces 
> on a body 
> > are also proportional to the body's mass. (A body's mass is just a 
> > measure of its inertia: to accelerate at an acceleration 
> "a", a force 
> > "F" must be applied, and the mass "m" is just F/a.)
> ......
> 
> 
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