What is Projectile?

A projectile is a body launched with a velocity $\vect v_0$ and then left in free fall. Axes at the launch point: $Ox$ horizontal in the vertical plane of $\vect v_0$, $Oy$ vertical upward; the launch angle $\alpha$ of $\vect v_0$ above the horizontal fixes its coordinates $(v_0\cos\alpha,\; v_0\sin\alpha)$.