There is a saying that two kind of waves are generated when an explosion happens. one moves slow which can carry the object away .when someone fires with a pistol, the bullet is pushed by this kind of wave . the other is different , it move fast ,maybe at 8000m/s. I wondered how this is possible. Can anyone explained it in a understanding way? I only knows the basics about physics. and thanks for a little reference , for example ,some terminology which i can use to look up in wikepedia.