
429Shock Physics
This velocity is to the left because we used a left-going Hugoniot. Notice that we used u
0
− u
1
in place of u
1
because the shock velocity is relative to the wave.
When a shock wave propagates from a lower impedance material into a higher imped-
ance material, as always, the compatibility condition is such that the pressure must also
be continuous at the interface and the particle velocities must be equal. The higher imped-
ance material will cause the pressure to increase and this higher pressure wave will propa-
gate back into the lower impedance material (but at a lower velocity) and into the higher
impedance material at a lower ...