Principles of Projectile Motion

Since the same motion can be viewed from multiple frames of reference, physicists must be able to agree on the results.  This means that we must be able to separate vertical and horizontal motion and analyze them separately.  If the initial horizontal motion changes, this should have no effect on the vertical motion, and if the initial vertical motion changes, this should have no effect on the rate of horizontal motion.

Our kinematics equations still apply in both the horizontal and vertical directions, but they are greatly simplified in the horizontal direction, as there is no acceleration horizontally.  The common variable for horizontal and vertical motion is time of flight.  Every other value is specific to either the horizontal or vertical motion.