Hello all. I'm currently looking at developing a realtime physics engine based on energy concepts. It will model all objects as soft-bodies but I need some source material that gives information on the time taken for energy to transfer between particles. I know that the transfer of this energy is not instantaneous, otherwise all bodies would be rigid (which they aren't), but, unfortunately, I cannot find any material that discusses such a concept. If you look at a golf ball being hit by a driver during a very small time interval, it is clear that the kinetic energy is transferred across the material not instantaenously, but incrementally. Different materials transfer this energy faster, or slower. Are there any books or papers that look at this in more detail? All I can find are extremely abstract analysis. No equations are offered. I appreciate any help.