Vectors and Projectiles - Mission VP9 Detailed Help

A projectile is launched horizontally. As it travels along its trajectory towards the ground, the horizontal component of its velocity ____ and the vertical component of its velocity ____.

Definition of a Projectile:
projectile is an object for which the only force acting upon it is gravity. The force of air resistance is negligibly small or nonexistent for a projectile.

A horizontally-launched projectile will continue to move in the horizontal direction at a constant speed. Gravity - a vertical thing - is independent of any horizontal component of motion and does not affect the horizontal velocity. The force of gravity does cause a change in the vertical velocity of a projectile. Being a downwards force, gravity causes a falling object to speed up. So after being launched horizontally, the projectile immediately begins its downward fall with an increasing speed.