Projectile motion involves two-dimensional motion where the vertical and horizontal components are independent. Vertically, projectiles experience constant acceleration due to gravity. Horizontally, projectiles experience no acceleration and maintain a constant velocity. As a result, the vertical motion of a projectile follows a parabolic trajectory, while its horizontal motion remains unchanged. Both cannonballs released simultaneously will hit the ground at the same time since their vertical motions are identical, despite differences in their horizontal velocities.