I was wondering how to do the math for a bullet hitting some body armor. Would you just divide the original force of impact by the area of a the circle surrounding the point at lets say 3 inches? So.. lets say I gave a bullet moving 1500 m/s at 1g. so it would be .5(1)(1500^2)=1125kJ joules. (I know that these aren't the right speed and mass) So, at 3" you would divide 1125/9pi? This is a high school level project, so I'm hoping the math isn't very complicated. Another problem is the use of different materials for the body armor, whether ceramics, steel or something else..