The purpose of the two studies presented in this paper is to establish validity evidence for the Sport Multidimensional Perfectionism Scale-2 (Sport-MPS-2: Gotwals & Dunn, 2009). Studies 1 and 2 are respectively focused on the production of structurally-related and external validity evidence.
The horizontal velocity of a projectile is constant (a never changing in value), There is a vertical acceleration caused by gravity; its value is 9.8 m/s/s, down, The vertical velocity of a projectile changes by 9.8 m/s each second, The horizontal motion of a projectile is independent of its vertical motion.
For instance a paper airplane is a projectile, once it is thrown the only force acting on it is gravity. An airplane with an engine is not a projectile, the engine continues to give the plane a force. Projectiles have a vertical velocity and a horizontal velocity. The vertical velocity will accelerate because there is a force of gravity changing the velocity in the vertical plane. The horizontal velocity is constant. According to Newton's 1st Law and object in motion stays in motion until a force acts on it.