Ok, I'm using Schaum's Outline of College Physics to supplement my ultra condensed correspondance physics course. As I work through the "Supplementary Problems" I've come across this one which leaves me puzzled. Typically a bullet leaves a standard 45 caliber pistol (5.0 inch barrel) at a speed of 262 m/s. If it takes 1 ms to traverse the barrel, determine the average acceleration by the 16.2 g bullet within the gun and then compute the average force exerted on it. The provided answers are: 3.0 x 10^5 m/s, 0.4 x 10 N. I've had no problem working out the average acceleration to 2.62 x 10^5 m/s (3.0 X 10^5 m/s), but I have no idea how the book has arrived at 40 N for the average force exerted. Does anybody care to show how this was worked out?