Reading over the source on the example apps, the first thing that jumps out at me is _underscore _prefixed _variables and it just looks odd in ruby, especially with :_symbols
Unless I'm mistaking inertial scrolling has nothing to do with it bouncing back specifically, it's inertial meaning having inertia, the tendency for something in motion in this case tr window to stay in motion unless acted upon by an external force. Bouncing when you reach the end would be a simulation of elasticity not enertial