# Bullet shot vertically up
#
# z'' = -g -af = -g -k*v^2
#     with k = 1/m * 1/2 * A * c.w * rho 

coefficient.1(-1) -> -g    # gravity
coefficient.2 -> k         # coefficient of friction
coefficient.3(+1) -> v0    # initial vertical speed

iintegrate (-g, 10*: friction) -> -v
  IC: v0
iintegrate (-v) -> z

invert -v -> v

multiply (-v, -v) -> v^2
cmultiply (k, v^2) -> kv^2 

# make sure friction acts against the direction of propagation
invert kv^2 -> -kv^2
compare v -> friction 
  GT0: -kv^2   # v > 0 => moving upwards
  LT0:  kv^2   # v < 0 => moving downwards
  
output (v)        -> out.x
Output (friction) -> out.y
output (z)        -> out.z