Where m is the mass or relativistic mass of the body, m0 is the mass at rest, or proper mass and v is the velocity.

where m is the mass at rest (or proper mass) of the particle and u is its Quadri-velocity

Global mass will be a mass at rest plus the increase in this mass due to the increase in velocity.

L, p and m are the Universe line, Quadri-impulse and mass at rest (or proper mass) of the particle.

The rest mass is always the same for the same type of particle.

Thus, any particle traveling at c must be massless.

Yes, all massless particles travel at the speed of light relative to all observers, and all massive particles can never attain that speed.

The trick is to measure always the mass at rest, and if the object moves within a system, to integrate it into the physical system, calculating the mass of the whole system at rest.

In a world such as ours, a particle can split only if the sum of the masses at rest (the mass when the particle is immobile) of the particles produced is lower than the mass at rest of the initial particle.

In a world such as ours, a particle cansplit only if the sum of the masses at rest (the mass when the particleis immobile) of the particles produced is lower than the mass at rest of theinitial particle.

In a world such as ours, a particle can split only if the sum of the masses at rest (the mass when the particle is immobile) of the particles produced is lower than the mass at rest of the initial particle.

The term, Matter, is used in reference to a substance (often a particle) which has “rest mass”.

elementary particle with one positive electric charge of +e and the same rest mass as the electron

In fact, they behave like Heisenberg’s relative particles, with an effective resting mass of zero.

Let us multiply both sides of the acceleration transformation equation by the constant rest mass m0: