I have been trying to learn how to make multi-player games. One thing I learned is that making multi-player games is more difficult than single player games and involves lot of challenges that are not present in single player games. One such challenge is to implement game physics in them. I learned the basics and decided to share my knowledge, and hence wrote two articles for beginners like me. If there is some mistake please tell me 
Synchronizing Game Physics in Multiplayer Games - http://blogs.shephertz.com/2013/08/16/next-level-synchronizing-game-physics-in-multiplayer-games/
Game Physics in Multiplayer Game Development - http://blogs.shephertz.com/2013/08/13/game-physics-in-multiplayer-game-development/