Query regarding to the state of frame of reference for the ball

[aditya ver.2.0]

If a metallic ball is place under a giant hollow top, and the top starts to rotate. Along with the top, the metallic ball will also start to rotate. Thus my question is the ball motion is under inertial frame of reference or non-inertial ?

 

[mfb]

You can choose an arbitrary system to describe the setup, both inertial and non-inertial frames are possible.
If you asked something else, I don't understand what the question is.