Recoil being another term for mass. That force, applied to a mass, creates an acceleration, which when applied over time, changes the velocity of a mass. According to Newton's second law, the law of momentum -- changing the velocity of the mass changes its momentum, (mass multiplied by velocity). It is important to understand at this point that velocity is not simply speed. Velocity is the speed of a mass in a particular direction. In a very technical sense, speed is a scalar (mathematics), a magnitude, and velocity is a vector (physics), magnitude and direction. Newton's third law, known as conservation
Four-velocity are multiplied by the four-velocity, one then gets new physical four-vectors that have 4 independent components. For example: Effectively, the formula_27 factor combines with the Lorentz scalar term to make the 4th independent component Using the differential of the four-position, the magnitude of the four-velocity can be obtained: in short, the magnitude of the four-velocity for any object is always a fixed constant: The norm is also: so that: which reduces to the definition the Lorentz factor. Four-velocity In physics, in particular in special relativity and general relativity, a four-velocity is a four-vector in four-dimensional spacetime that represents the relativistic