Solving horizontal projectile problems requires good organization and attention to detail. You must recognize which values belong in the horizontal analysis and which belong in the vertical analysis and must not confuse the two. Horizontal projectiles have no initial vertical velocity, which makes some of the vertical analysis easier. As is the case in all projectile problems, there is no acceleration in the horizontal direction, which means that velocity is constant and the analysis is very much simplified. In the vertical direction, acceleration is always due to the gravitational acceleration. The only variable common to both horizontal and vertical motion is the time of flight. Next, we will take a look at projectiles that are launched at an angle and learn to recognize the similarities and differences of solving such problems, using your earlier study of freefall to recognize some shortcuts.
For more information on projectiles view the video clip Projectile Motion from Discovery Education™ streaming.