The kinetic energy transfers from the moving ball to the non-moving ball.
We have sequence equation
.
In this case n is a natural number (1, 2, 3, ...).
So start inserting and computing value of
given that you know the value of n and a.
(first term)

Hope this helps.
An example of a two dimensional object is a price of paper or a drawn figure on a paper because it has no height or depth
28 divided by 3 is 9.33333333
3 divided by 28 is 0.10714286