Is there any physics engine SDK for iPhone/iPod touch and iPad?
The Chipmunk engine is written in C, and they've even provided an Objective-C wrapper.
The Box2D engine is written in C++, and so it can be compiled/linked into an iPhone OS project by telling Xcode to treat it as Objective-C++.
Both are excellent. (I've only extensively used Box2D, but I've heard great things about Chipmunk too.)
I've used the SIO2 engine for developing games on the iPhone, and it uses the open-source physics engine bullet. I'm not sure if all the soft-body features are available, but certainly the rigid body ones are. I don't know if anybody has written an Objective-C wrapper, but you certainly don't need one.
来源：https://stackoverflow.com/questions/2695724/is-there-any-physics-engine-sdk-for-iphone-ipod-touch-and-ipad