# Momentum (Conceptual) Question

Suppose there is a cannon that shoots a cannon ball at a certain angle above the horizontal (a projectile). Since momentum is conserved in both directions, the cannon should posses a velocity now in the y (or z-axis if you would like to call it) and in the x axis.

1) However, what does it mean for a cannon to be moving down into the ground?
2) Also, if a question was asked saying what is the velocity of the cannon relative to the ground, would I use use the x-velocity or the vector sum of the x and y (or z) velocities (ie get the resultant)?