I. If you don't push it, it won't move. 
    II. If you push it, it will move. 
   III. If you push it, it pushes back. 

These sentences are simplified versions of three very basic, yet complex, ideas
about how forces affect the motion of objects.  When Sir Isaac Newton, the
English mathematician and scientist, published these three Laws of Motion in
1687, roller coasters as we know them today did not exist.  But his ideas form
the basis upon which designers create roller coasters that give you thrills and
chills without the spills.