Lev Landau derived an operator named for these phenomena that contains the term [read slowly] “f star times the divergence of f minus f times the divergence of f star.” An operator named for these phenomena is simplified to a scalar “frequency” in a lattice model named for Bhatnagar, Gross, and Krook. Steady-state solutions to an equation named for [emphasize] not including these phenomena (-5[1])correspond to functions of the integrals of motion according to Jeans’s (10[1])theorem. The Stosszahlansatz (“sh’TOAST-sahl-ahn-zahts”) assumes that the (-5[1])velocities of particles (10[1])undergoing these (10[2])phenomena (10[1])are uncorrelated (10[1])and independent of position. (10[1])The primary use of the center-of-momentum frame (10[1])is (10[1])to (10[7])study these events. (10[1])Mean (10[1])free (10[1])path (10[1])gives (10[2])the average distance traveled (10[1])between these events. For 10 points, name these events that in ideal gases are always assumed to (10[1])be elastic. ■END■