I'm writing a talk on ballistics and was looking for the formula for the distance travelled by the projectile. However, all the formulae I have found exclude air resistance. I understand that the effect of air resistance depends on how stream-lined the projectile is, but is there not a general formula? Also, the formula for distance travelled (when air resistance is neglected) changes if the projectile is not travelling over a flat surface. Why is that? If anyone has the answers to those two questions you'd be a real life saver.