V. Petkov, Note on inertial forces, inertial energy and the origin of inertia (click on title to read the paper)
**Abstract:** As a result of the open question of inertia the status of inertial forces has been a difficult subject in physics with
implications for the proper understanding of the force of weight in general relativity where gravity is not a force, but a
manifestation of the spacetime curvature. The purpose of this note is fourfold. First, to state explicitly when the
inertial forces are fictitious and when real. Second, to provide a virtually self-evident derivation, which demonstrates
that kinetic energy is in fact inertial energy - the energy equal to the work done by inertial forces. Third, to stress
that weight, which has been traditionally regarded as a gravitational force, is an inertial force in general relativity.
Fourth, to outline what spacetime physics implies about the origin of inertia.

Quote as: V. Petkov, "Note on inertial forces, inertial energy and the origin of inertia," *Minkowski Institute Physics Journal*, 30 October 2020

V. Petkov, Relativistic Mass is an Experimental Fact (click on title to read the paper)

**Abstract:** Since mass is defined as the measure of the (experimentally established) resistance a particle offers to its acceleration and as it is also an experimental fact that a particle's resistance to its acceleration increases when its velocity increases, it follows that, like mass, the concept of relativistic mass also reflects an experimental fact. This means that the rejection of the relativistic velocity dependence of mass amounts to both rejection of the experimental evidence and refusing to face and deal with one of the deepest open questions in fundamental physics - the origin and nature of the inertial resistance of a particle to its acceleration, i.e., the origin and nature of its inertial mass.

Quote as: V. Petkov, "Relativistic Mass is an Experimental Fact," *Minkowski Institute Physics Journal*, 10 January 2023

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