Newton's Cradle model. Nice UI, drag and drop the balls to create motion or use accelerometer.
v2.2.0: Multi-touch support for Android 2.0+
v2.1.1: Donut 1.6 update with QVGA & WVGA support
It works, but is boring — Yes this is the classic Newton's Cradle but it is very basic. The physics are all there, but how long do you really play with this before you've had enough. For me it was about a minute and that was it. The balls can be changed to 1 of 3 different settings. You can use the accelerometer to swing...