Google SketchUp plugin that runs simulations based on real-world physics
During the simulation, SketchyPhysics applies Newtonian physics laws to grouped objects, with runtime user interactivity added through an on-screen object dragging system, using the mouse to pull objects around.
Joysticks and a simple joypad button or keyboard input are supported to control a selection of joints and settings applicable to grouped objects, including self-replicating emitters, thrusters, magnets, and more.
In addition, limited Ruby script use is supported for more advanced actions; for instance of SketchyPhysics in action, please install SketchyPhysics on your PC/Mac, and search for 'Sketchyphysics' on the Google 3D warehouse.
SketchyPhysics employs the Newton Physics Engine from Newton Game Dynamics to drive the simulations.
Detailed instructions on how to install and use the SketchyPhysics utility on your Mac are available HERE.
SketchyPhysics is cross-platform and it works on Mac OS X and Windows. Binaries for the Windows platform are available on the project's homepage.