This week's book giveaway is in the General Computing forum. We're giving away four copies of Arduino in Action and have Martin Evans, Joshua Noble, and Jordan Hochenbaum on-line! See this thread for details.
I'm new at learning Objective-C along with the iPhone SDK. I have an app idea but it involves some physics with objects. I started coding collisions myself but am now in a bind. I researched some open physics engines (Box2D and Chipmunk). Would you suggest using these in your app? Which one do you prefer?