Please enroll in an elementary Physics course at your local High School.
1. I work at my local High School.
2. I passed both NYS Regents physics AND college physics with calculus with high marks none the less.
3. Want me to decompose your vector? Here you go:
Let's say you are in free fall with no movement except directly down, like you jumped out of a helicopter (yes I know they can't go that high).
So your acceleration is 9.8m/s^2 down. That can be broken into X = 0, Y = 9.8m/s^2, Z = 0
Working against you is drag. Drag varies with velocity, surface area, and resistance of the medium. As your velocity increases the drag also increases. Once Drag, which is a force, becomes equal to your weight, the acceleration vector becomes 0 and you're in terminal velocity.
So unless I'm mistaking the definition of "decomposing vectors", I don't see the problem here.