Momentum motion. The first use of "momentum" in its proper mathematical sense is not clear but by the time of Jenning's "Miscellanea" in 1721, five years before the final edition of Newton's "Principia Mathematica", momentum or "quantity of motion" was being defined for students as "a rectangle", the product of and , where is "quantity of material" and is "velocity", . Momentum In Newtonian mechanics, linear momentum, translational momentum, or simply momentum (pl. momenta) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction in three-dimensional space. If is
Mass in special relativity Mass in special relativity Mass in special relativity incorporates the general understandings from the laws of motion of special relativity along with its concept of mass–energy equivalence. The word "mass" is given two meanings in special relativity: one ("rest" or "invariant mass", and its equivalent "rest energy") is an invariant quantity which is the same for all observers in all reference frames; the other ("relativistic mass" or the equivalent "total energy" of the body) is dependent on the velocity of the observer. The term "relativistic mass" tends not to be used in particle and nuclear physics and is often avoided