  In this paper, two kinds of occurrence mechanism on the phenomenon of
concentration and the formation of delta shock waves are analyzed and
identified in the flux approximation limit of Riemann solutions to the extended
Chaplygin gas equations with Coulomb-like friction, whose special case can also
be seen as the model of the magnetogasdynamics with Coulomb-like friction.
Firstly, by introducing a transformation, the Riemann problem for the extended
Chaplygin gas equations with Coulomb-like friction is solved completely.
Secondly, we rigorously show that, as the pressure vanishes, any two-shock
Riemann solution to the nonhomogeneous extended Chaplygin gas equations tends
to a {\delta}-shock solution to the corresponding nonhomogeneous transportation
equations, and the intermediate density between the two shocks tends to a
weighted {\delta}-measure that forms the {\delta}-shock; any
two-rarefaction-wave Riemann solution to the nonhomogeneous extended Chaplygin
gas equations tends to a two-contact-discontinuity solution to the
correspongding nonhomogeneous transportation equations, and the nonvacuum
intermediate state between the two rarefaction waves tends to a vacuum state.
At last, we also show that, as the pressure approaches the generalized
Chaplygin pressure, any two-shock Riemann solution to the nonhomogeneous
extended Chaplygin gas equations tends to a delta-shock solution to the
correspongding nonhomogeneous generalized Chaplygin gas equations. In a word,
we have generalized all the results about the vanishing pressure limit now
available for homogeneous equations to the nonhomogeneous case.
