If that is the definition of KE when applied to archery, the formula does not take into account what happens when friction increases dramatically when an arrows path is diverted in the body of an animal - and it always is, at least a little. I'm not an engineer, but I do not believe that KE is a good indicator of pentration potential of broadhead tipped arrow passing through an animal's body. Plain and simple, it's dead last on my list of concerns. However momentum is not dead last. It's a step ahead of KE. The reason is simple. I know that with no more effort on the shot, I can decrease the likelihood of deflection by simply increasing momentum in the easiest manner - using a heavier arrow. Since momentum is increased at a greater rate, it has to have more importance than a factor that is increased by a lesser rate. If it wasn't true, then it wouldn't matter if I just increased KE by drawing more poundage. However, it does matter. Increasing arrow weight has a more significant influence on momentum with no more effort.