G-force question

Near my place there is a new amusement ride called the ‘Vomitron’. It has a large arm that spins around and around, with two cages at each end of the arm for two passengers each. It is very much like a centrifuge that they use for pilot training.

There is a lot of screaming when this thing runs, and it does indeed live up to it’s name and make people sick.

My question is this: What kind of g’s would you be pulling in this thing?

My estimates put the cages at the end of the spinning arm to be travelling at about 90km/h.

Is there a special formula for centrifuge g calculation?