add gravity to ruther code?

Hi, I am doing an computer simulation of Rutherford's scattering experiment, I have been using this code http://www.mathworks.com/matlabcentral/fileexchange/2268-projects-for-scientists-and-engineers/content/penland/ruther.m as a starting point. The problem is I need to add gravity to the experiment but I am unsure as to what "point of view" is being seen in the matlab fig displayed. If a anyone could help me with clarifying how I could add the gravity component and to the code and what point of view is seen it would be greatly appreciate. And also how could various graphs be plotted from the same code but displayed on separate windows , ie total Energy vs t, kinetic energy vs time and potential energy. THANKS A MILLION TO ANYONE WHO HELPS