10.4 Elastic-inelastic

We shall often be interested in cases where we transfer both energy and momentum from one particle to another, i.e., we have inelastic collisions where particles change their character – e.g., their rest-mass. If we have, as in Fig. 10.3, two particles with energy-momentum $k_1$ and $p_q$ coming in, and two with $k_2$ and $p_2$ coming out, We know that since energy and momenta are conserved, that $k_1+p_1=k_2+p_2$, which can be rearranged to give

and shows energy and momentum getting transferred. This picture will occur quite often!