macOS Open source Objective-C physics framework?

[Ja Di ksw]

Hi everyone,
I would like to program a static 2-D world that will involve circular objects moving around (imagine them in water, viewed from the side, so they won't be stuck to the bottom and I don't have to worry about them rolling). I'll need some global affects such as "gravity," but I'm more worried about collisions between the circular objects. Are there any open source frameworks that I would be able to incorporate which can handle collisions, deformation, etc? I would assume a game engine would have some of these already figured out, but I don't know if there's something a little more simple that's open source so I don't have to buy an engine that's way more complicated than I need.
Thanks in advance!

 

[Blakeasd]

Chipmunk is relatively popular and has Objective-C bindings available.

 

[960design]

Open source not so sure, but I've used:
1) Torque2D & 3D
2) Blender Game Engine
3) Unity
4) Cocoa/Box2D


I like Cocoa/Box2D's performance but usually prototype in Unity. I started with Torque way back in the day and moved to BGE for simple testing. BGE has really improved from what I've read, but I haven't used it beyond those demo tests.

PS There's also UDK but I haven't used it in development.

 

[Ja Di ksw]

Thank you for the suggestions!

 

[subsonix]

Perhaps have a look at the new Sprite Kit that is part OS both iOS 7 and OS X Maverics.