How cannon ball become a satellite?
a. Think of cannon ball falling in parabolic shape. The trajectory drawn by the cannon ball is actually part of an elliptical orbit that focuses on the center of the earth. The center of the earth corresponds to the far focus of the ellipse.
b. To prevent cannon ball from colliding with the surface, it should be fired horizontally to the surface at a speed of at least 8 km / s (exactly 7920 m / s). If the speed is faster than this, the cannon ball does an elliptical movement with the center of the earth as the near focus of the ellipse.