http://www.vibrationresearch.com/blog/wp-content/uploads/2013/05/fma2-700x450.jpg
http://www.lightandmatter.com/html_books/lm/ch06/ch06.html
http://colgatephys111.blogspot.com/2011/11/physics-of-bullet-drop-problem.html
http://www.school-for-champions.com/science/images/gravity_horizontal_motion_curved_earth.gif