The amount of force acting on a piece of pro during a fall is a factor of several things (weight of climber, length of fall, the amount of stretch in the rope, harnesses, bodies, etc, and the "fall factor". The "fall factor" is the ratio of the total distance the leader falls to the amount of rope out. So, if the leader falls above the anchor with no gear, that is a factor 2 fall. (Leader falls twice the rope length).
I'm no physicist either (I'm a geneticist), so I don't know the formula to calculate the force of a fall (the rope stretch issue is complicated I think), but I think a factor 2 fall (falling from 10 feet above anchor to 10 feet below anchor) generates twice as much force as a factor 1 fall (falling 5 feet above your piece of gear which is 5 feet above anchor for a total of 10 feet of rope).
This is why factor 2 falls are BAD. Always put a piece of gear in above the anchor, even if it's easy climbing. Don't fall on the anchor.
Damn my brain hurts...
I need a beer....