Hi,
You need to abstract the "scroll" value and work out the speed of the touch drag, then when the user release you decrease the speed.
So the scrolling behavior has two very distinct part, the system that computes the scrolling value ( touch, decelleration) and the scroll view itself. The scroll view is only exposing a scroll variable, and the touch system will inject the scroll value.
During drag, you don't use the speed, you only use the delta position of the drag, when releasing the touch, you then use the speed ( that you decrease over time) to keep computing the delta position.
Does that make sense?
bye,
Jean