Physics2D
Physics2D.net is 2 dimensional rigid body physics engine written in C#.
It is CLS compliant. Currently it has only one broad phase collision detector and collision solver. The narrow phase collision detector is considered to be part of the solver. The broad phase collision detector is sweep and prune. The Solver is Sequential impulses with a distance grid used for narrow phase detection.
Link:Aici

Slab daca te gandeshti la cerintzele pt GM,inceraca GMPhysics,cel mai bun engine fizic 2D are multe functzii:Rigid Body,RagDolls,Fluid,Water,Particles,Joints,Raze Laser,Custom Poly,AutoPoly(care face polygoane dupa o imagine automat) cu de tectzie de normale shi este foarte rapid,pt. creatori de jocuri fara GM este posibil sa il foloseasca
aici este linkul http://host-a.net/coderchris/betabeta.zip