In special relativity, four-momentum is the generalization of the classical three-dimensional momentum to four-dimensional spacetime. Momentum is a vector in three dimensions; similarly four-momentum is a four-vector in spacetime. The covariant four-momentum of a particle with three-momentum vec p = (p_x, p_y, p_z) and energy E is » egin This allows the potential energy from the charged particle in an electrostatic potential and the Lorentz force on the charged particle moving in a magnetic f… (More on 4-momentum)