Projectile motion
= Projectile motion
Motion after launch under a specified <gravitational field>, with negligible <drag force> and no thrust. In a constant downward <gravitational acceleration> $g$, horizontal <velocity> is constant and vertical <position> obeys $y(t)=y_0+v_{y0}t-gt^2/2$. Eliminating time gives a <parabola> when horizontal velocity is nonzero. Over larger distances the changing direction and magnitude of gravity require an orbital model instead.