I created a quick, very low profile physics demo and exported to both appMobi and CocoonJS. This is just a bird's eye view of a large object moving about 20 small objects along a tiled background. That's it.
To my disappointment, the frame rates were horrid on both frameworks on a 3rd generation iPad. I've cancelled this project, since it would be unplayable on the device I targeted it for. Sorry, but both CocoonJS and appMobi render physics games on Construct 2 for any mobile devices worthless.