there are a lot of physics engines, you may select one for you. For example, ODE is a little bit faste, but Newton is more precise

Example of using Newton you can see at the contest, or you can find link in my signature wink

1st prize: Lite-C and Newton 2.17 by Vasilenko Vitaliy

Newton2 videos: http://tinyurl.com/NewtonVideos
LiteC+Newton2 discussion: http://tinyurl.com/NewtonWrapperDiscussion
Latest LiteC+Newton2 version(v23, from 29.10.2009): http://depositfiles.com/files/ae1l0tpro