Hmmm, I'd like to do some research into the physics of how blades cut things, I wonder where I should start.
It's interesting though. One of my knives is sharp enough to cut skin like tissue paper, but light targets like bottles simply bounce off of it. Another one of my knives of a similar design is so dull that it practically can't cut skin, and yet it cuts light targets nearly as well as my katana. I assume this has something to do with the geometry of the blade, but I can't be sure. It's really interesting to me though.