Centripetal Motion on a Semi-Rollercoaster

[Procrastinate]

http://cache.rcdb.com/pictures/picmax/p5740.jpg
I am doing an analysis on a roller coaster that is represented on the diagram attached.

However, I am having trouble analysing the curve. The radius is 36.9m and it is 160km/hr going up and then it free falls back down from 115m for about three seconds.
When I am going up do I just use a_centripetal = v^2/r to find the acceleration?
When I am going down, I have to find the acceleration as well as the velocity, but how do I know where to start?

 

[masqau]

u know the figure look like a function f(x)=exp(-x).
the above function mean that "x" is linear and than it decay exponentially as u can see in ur figure.