Try the applet demo or launch it here
Download (Compiled with sdk 1.3)
Sourcecode: GravityTest.zip (NetBeans project).
NOTE: You have to download the Phys2D library and add it to your CLASSPATH.
Go to http://phys2d.cokeandcode.com/ and download the phys2d.jar and add it to the classpath. If you are using NetBeans click on Libraries > Add jar/folder and select it. You have also to change the video url in BodyConstants.fx you have to point to a remote .wmv file. If you point to a local file system it may not work.