Do you have Wolfram System Modeler? It might helpful to do the simulation with that if you are planning on adding many components.

Otherwise the first step is to write out the differential equations governing your system. For some examples on how Mathematica handles differential equations, take a look at the documentation for NDSolve:

http://reference.wolfram.com/mathematica/ref/NDSolve.html

Hi Friends. Thank you all. My main challenge is the "Hello World" , but in a scenario of a spring , one meter from the floor , with a mass on the top , as conected systems , and having a animation of the fall ... The equations will be another issue , once we will have this parameters on the real time during the lunar landing. ( http://www.googlelunarxprize.org/teams/spacemeta ). I m still thinking if Mathematica is a good tool for it , but it smell really good. Thanks ...