9.4: Elastic-inelastic
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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 Figure \PageIndex{1}, 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 p_2=p_1+q,\quad k_2=k_1-q. \nonumber and shows energy and momentum getting transferred. This picture will occur quite often!
