Starting from the energy balance within a quasistationary flame front the principal dependence of the flame front velocity on the physical properties of the mixture are modeled. In closed systems (e.g. S.I. engines, bombs, etc.) however, flame propagation may lead to feedback processes accelerating the front velocity until infinity. The model calculation predicts two feedback processes: flame acceleration by turbulence enhancement and flame acceleration by enhancement of the temperature of the end gas. Comparing available engine data from the literature on knock effects with the model predictions indicates full agreement in all observed and predicted dependencies. It is concluded therefore that the proposed model is very promising in providing a quantitative description of knock.