OK, im trying to make an iphone version of a game i made here http://scratch.mit.edu/projects/techy/781198 is box2d or chipmunk better and where are some tutorials for each one
I prefer Box2d - I think it is easier to understand than Chipmunk. Here's a link to another question that lists many usefull resources:
Plus here are a few links to cocos2d / box2d tutorials:
http://www.raywenderlich.com/457/intro-to-box2d-with-cocos2d-tutorial-bouncing-balls
http://www.raywenderlich.com/606/how-to-use-box2d-for-just-collision-detection-with-cocos2d-iphone
And a great book Ray is making that I think will be an awesome resource:
http://www.raywenderlich.com/2274/cocos2d-book-and-360idev
http://my.safaribooksonline.com/9780132180863
Hope these help - Happy coding!