Oh you mean force over area...
http://www.youtube.com/watch?v=wEVf9bc8 ... h+div-r-14
his followup and application.
http://www.youtube.com/watch?v=u9mwy1aA ... re=related
Not smoking the dude in the solarplexus???
http://www.youtube.com/watch?v=xJzYxepD ... re=related
more of the same if your bored...
http://www.youtube.com/watch?v=uSmq2auwNLs&feature=related