Mass in special relativity the mass of a moving particle." When the relative velocity is zero, formula_33 is simply equal to 1, and the relativistic mass is reduced to the rest mass as one can see in the next two equations below. As the velocity increases toward the speed of light "c", the denominator of the right side approaches zero, and consequently formula_33 approaches infinity. In the formula for momentum the mass that occurs is the relativistic mass. In other words, the relativistic mass is the proportionality constant between the velocity and the momentum. While Newton's second law remains valid in the form the
Electron rest mass This quantity formula_5 is frame invariant and velocity independent. However, some texts group the Lorentz factor with the mass factor to define a new quantity called the "relativistic mass", formula_7. This quantity is evidently velocity dependent, and from it arises the notion that "mass increases with speed". This construction is optional, however, and adds little insight into the dynamics of Special Relativity. Since the electron mass determines a number of observed effects in atomic physics, there are potentially many ways to determine its mass from an experiment, if the values of other physical constants are already considered known. Historically, the