Added mass fluid quasi-momentum. Unsteady forces due to a change of the relative velocity of a body submerged in a fluid can be divided into two parts: the virtual mass effect and the Basset force. The origin of the force is that the fluid will gain kinetic energy at the expense of the work done by an accelerating submerged body. It can be shown that the virtual mass force, for a spherical particle submerged in an inviscid, incompressible fluid is where bold symbols denote vectors, formula_2 is the fluid flow velocity, formula_3 is the spherical particle velocity, formula_4 is the mass density
Mass–energy equivalence equivalence of mass and energy". In addition, Einstein used the formula , with being the energy of a system of mass points, to describe the energy and mass increase of that system when the velocity of the differently moving mass points is increased. In June 1907, Max Planck rewrote Einstein's mass–energy relationship as , where is the pressure and the volume to express the relation between mass, its "latent energy", and thermodynamic energy within the body. Subsequently, in October 1907, this was rewritten as and given a quantum interpretation by Johannes Stark, who assumed its validity and correctness ("Gültigkeit"). In