Sentermassenergier

Sentermassenergier is a term used in some theoretical discussions and teaching contexts to describe the portion of a system’s energy that is associated with its center of mass. It is not a standard, universally adopted quantity in mainstream physics, but it serves as a conceptual aid for partitioning total energy into center-of-mass contributions and internal contributions.

The name is a compound word built from elements meaning center, mass, and energy. Its usage tends to be regional or informal, appearing mainly in explanatory texts, thought experiments, or speculative discussions rather than in widely circulated peer‑reviewed literature. In those contexts, sentermassenergier helps illustrate how energy can be attributed to the collective motion of the whole system as opposed to internal motions.

In a classical multi-body system, the total kinetic energy can be written as the sum of the translational energy of the center of mass and the internal energy associated with relative motions. Specifically, the translational part is (1/2) M v_cm^2, where M is the total mass and v_cm is the center-of-mass velocity. Sentermassenergier is used to denote this translational contribution, along with any potential energy that depends solely on the mass distribution tied to the center of mass, while excluding internal vibrational or rotational energies that arise from relative motions.

Limitations include its frame dependence: the value changes with a shift to a different inertial frame, and it is not invariant under relativistic transformations. It is most useful as an instructional tool or heuristic in non-relativistic contexts and in simple simulations to aid energy accounting.

See also: center of mass, kinetic energy, internal energy, molecular dynamics, rigid body dynamics.