The game goes to 10-12 fps in some parts if you use high resolution in this range of cards. A little better, 20 fps at lower resolutions. The physics are active in the Nvidia control panel, and only works with SM 4.0.
With the latest drivers from Nvidia - 180.84 at least - the game has bugs in the textures on SM 3.0, but run fine with older drivers - i believe taht 180.48 work fine with SM 3.0 -. My advice is to use SM 3.0, the game runs a 50% or more better, and see the physics in the demo or the game with SM 4.0 , after passing a level.