Arthur, momentum is a vector quantity as it is the sum of two vector quantities (the product mass and the respective vertical and horizontal components of the velocity vector). Speed, on the other hand is also a scalar quantity.Differientating speed and velocity seems to besplitting hairs sincespeed is distance over time and so is velocity.But speed does not imply direction whereas velocity does, making velocity a vector quantity too (along with momentum).

But then again, as you mentioned,throw in the angular momentum of the spinning arrow and it's oscillations, andthe physics of the gamestart to get complicated!