Hi there,
App Inventor currently does not integrate with any game engine or physics simulation engine. The current support for game-like features is rather short, and although there have been many conversation (especially in the open source forum) about extending support for games, what's currently available can be found in the 'Drawing and Animation' drawer, which basically contains a Canvas, a Ball, and an ImageSprite components. You can do things such as movement, dragging, and flinging sprites, and if you get creative, you can do quite a bit with that.