Airsoft guns add excitement but also help in combat or any war type scenario. Once the BB or the little foam bullet leaves the gun, it has a magnitude and a vector. When the BB or foam bullet is fired, it forms a projective trajectory that looks like a parabola. Calculating the velocity will allow you to calculate the fps (feet per second). A good airsoft gun will have a higher fps which will give you the end result of having more range. After figuring out the velocity, it is easy to figure out the kinetic energy using the equation Ek=(1/2)mv^2. Using the equation you will plug in the velocity and the mass of the BB. Deciding whether an airsoft gun is good or not has a lot of factors. Barrel length effects the velocity and the projectile. The longer the barrel, the more stabilized of a projectile it will have and the BB will leave the barrel later. The barrels diameter also has an effect.