(this is a homework question)
To this, I would say that the centrifugal force is just the reactionary force of the centripetal force, which is causing the hammer to 'want' to move away.
Therefore, I would say that there is always a centrifugal force as it is just a reactionary force to centripetal force (even though its fictitious)
Basically, I want to know if this was correct. I have done some other reading, and I was wondering if the centrifugal force was instead caused by the tension on the string when the athlete was swinging the hammer around?