Difference between horizontal and vertical velocity.

When a projectile is flung/launched into the air it always follows a parabolic shape of symmetry. The horizontal motion of a projectile is constant and moves in one direction if friction (air resistance) is ignored. The vertical motion of a projectile does not stay constant instead decelerates to 0m/s at the the final height of its parabolic shape and then accelerates to the same velocity it was launched when it comes down, the projectile is forced to come down because the force of gravity is constantly pulling it down therefore slowing its upward motion.