ABSTRACT
This chapter extends the theory of relativistic mechanics to the interactions of particles. It is not necessary to develop the relativistic mechanics of a particle before deriving the Lorentz transformations. The Lorentz transformations and the relativistic velocity transformations can then be derived before even mentioning relativistic mechanics, which is then developed by seeing how the momentum of a particle must be redefined if, in the case of an idealized elastic collision, the laws of conservation of momentum and of energy are to obey the principle of relativity, when the coordinates and time are transformed using the Lorentz transformations. To illustrate the application of the conservation laws of relativistic mechanics, consider the elastic collision of particles 1 and 2 of masses m1 and m2 respectively. It is found that extra conservation laws are applicable in certain cases, such as the laws of conservation of charge, parity and baryon number.
