*Fundamental point:* The initial velocity is
not colinear with the force!

x(t)=v_{x}(0)t;
y(t)=v_{y}(0)t -½gt^{2}

Solve for t in the first equation, t=x(t)/v_{x}(0), and substitute in the
second equation to give:

y(t)=v_{y}(0)x(t)/v_{x}(0)
-½g[x(t)/v_{x}(0)]^{2}=
Ax+Bx^{2} **Parabolic
trajectory!**

Examples: thrown ball, bowling ball with sidespin, billiards masse shot.