A physics engine in Adobe After Effects is what a lot of motion grapher and VFX artists have wanted for a long time. A lot of the 3d packages (including the rudimentary Google's Sketchup) all have some sort of physics engine, but having to leave the program (and in some cases having to learn a new program) can become cumbersome.

So that's why Motion Boutique has introduced the Newton Physics Engine. Here are the main features:

. robust and fast
. simple and intuitive user interface with OpenGL preview
. gravity, collisions, friction, etc.
. support of masks and shapes
. handles different sorts of bodies: static, dynamic, kinematic, etc

For all those that are new to motion graphics or VFX, a physcis engine is computer software that provides an approximate simulation of certain physical systems, such as rigid body dynamics (including collision detection), soft body dynamics, and fluid dynamics, of use in the domains of computer graphics, video games and film (see Wikipedia)

Video's and a demo of the product can be seen here: Finally! A Physics Engine in After Effects | Fliques Osman