In the game ArmA 2 they try to simulate ballistics and have some kind of drag model. I would like to try to find out how it works. I collected the following data from a bullet fired from a rifle in the game. Initial Velocity: 900 m/s Time of flight: 0.000 sec 100m Velocity: 819 m/s Time of flight: 0.114 sec 200m Velocity: 746 m/s Time of flight: 0.226 sec 400m Velocity: 618 m/s Time of flight: 0.543 sec 600m Velocity: 512 m/s Time of flight: 0.913 sec 1000m Velocity: 352 m/s Time of flight: 1.835 sec The only given value given relating to the drag was "airFriction = -0.0009324". This is a negative value and I'm not sure how to calculate it using that formula. I would like to know how I can derive some kind of equation that will give the final velocity of a projectile launched at 900 m/s matching that of the projectile above, or at least more clues on how they decided to program their in-game ballistic physics.