Yeah, here is a short history...
The Physics Helper Library was first created for Silverlight 2. In Silverlight 2, Behaviors did not exist yet (they were introduced in Silverlight 3), so at that time the Physics Helper used UserControls to operate. The following videos show this older way
of using the Physics Helper:
Brian Peek interviews Andy Beaulieu on the Physics Helper. Note that this demos Version 1, which is based on the User Controls instead of Behaviors.
MIX09 SHOW OFF!
The Physics Helper Library took 1st Place at the 2009 MIX Show Off! Event. This is the winning video.
LEGACY GETTING STARTED
This older Getting Started video uses Version 1, which is based on the User Controls instead of Behaviors.
Then, when Silverlight 3 was released, Behaviors were introduced which are _perfect_ for this sort of thing! So I refactored the code a bit and added Behaviors wrappers for the Physics Helper controls. These videos show the newer way of using the Physics Helper
VIDEO ON "THE BASICS"
This is an intro video on using the Behaviors to apply Physics in Expression Blend.
VIDEO ON "JOINTS + PROGRAMMING"
A more advanced video on using Behaviors to create Joints and accessing objects via code-behind.
VIDEO ON "FLUID CONTAINER"
A short video on using the Fluid Container Behavior to simulate water.