From: julio@diegidio.name
On Friday, 23 December 2022 at 16:09:41 UTC+1, Hendrik van Hees wrote:
> On 23/12/2022 08:24, Luigi Fortunati wrote:
> The equations of motion of Newtonian mechanics for point particles with
> constant mass are always defined with reference to an inertial frame of
> reference, and you get the equations describing these Newtonian within a
> non-inertial reference frame simply by writing the coordinates of the
> point particles wrt. an inertial frame in terms of coordinates referring
> to a non-inertial frame.
>
> This leads to additional terms when taking the time derivatives.
Please correct me if I am mistaken, but F=ma is not only valid in inertial
frames, is it? Indeed, I find the way you are presenting things here still
risks to give the impression that these "fictitious", aka "apparent" forces
are only an artefact of the algebra, while in that sense they are rather a
misnomer for the quite real forces an observer in that non-inertial frame
would feel and measure. Put simply, if one jumps on a merry-go-round,
fighting the centrifugal force is a real and properly physical thing, no?
Julio
[[Mod. note --
1. Just to be clear: the quoted text was written by Hendrik van Hees,
not by Luigi Fortunati.
2. I agree with Hendrik: F=ma (with F only including "real" forces) is only
valid in an inertial reference frame. To do Newtonian dynamics in a
non-inertial reference frame, one must augment F to also include
fictitious forces (such as the Coriolis force).
3. From a Newtonian-dynamics-in-an-inertial-reference-frame perspective,
if I jump on (and hold on to) a merry-go-round, I don't feel a
centrifugal force. Rather, the merry-go-round exerts a *centripetal*
force on me, accelerating me inwards (so that I move in a circle around
the rotation axis). The *centripetal* acceleration is what I feel.
-- jt]]
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