  The notion of inertial reference frame is abandoned and I replaced it by a
local reference frame on which the fundamental law of mechanics is expressed.
The distant interactions of cause and effect are modeled by the propagation of
waves from one local reference frame to another. The derivation of the equation
of motion on a straight segment serves to express the proper acceleration as
the sum of the accelerations imposed on it, in the form of an orthogonal local
Helmholtz-Hodge decomposition, in one divergence-free and another curl-free
contribution. I wrote the inertia term in the form of a gradient of a scalar
potential and a dual curl of a vector potential. The adopted formalism opens
the way to a reformulation of the material derivative in terms of potentials
and allows me to remove the fictitious forces from continuum mechanics. The
discrete equation of motion, invariant by rotation at constant angular
velocity, is used to conserve the angular momentum per unit of mass, in
addition to the conservation of energy per unit of mass and acceleration. All
the variables in this equation are expressed only with two fundamental units,
those of length and time.
