What particle systems are you talking about?  Processing does not have any built in particle physics.  Maybe your thinking of the Traer Physics or Toxi Physics library?

Yea, I suppose you be right.  I was looking at Shiffman's particle physics examples, thinking it was a core library.  Appears it is not really a library.  Of course, I found this page right after I posted which has been helpful, as well as looking into vectors;