DISCUSSION THREAD

Here you will use the moving reference frame kinematics equations:
          v_A = v_C + (v_A/C)_rel + ω x r_A/C
          a_A = a_C + (a_A/C)_rel + α x r_A/C + 2ω x (v_A/C)_rel + ω x (ω x r_A/C)

With the observer attached to the disk:

• The angular velocity of the observer is the vector sum of the angular velocity of arm OC and the angular velocity of the disk relative to the arm:
            ω = ω₁ J + ω₂ i
  where J is a fixed axis and i is a moving axis.
• The angular acceleration is the time derivative of the angular velocity vector: α = dω /dt.
• For the (v_A/C)_rel and (a_A/C)_rel  terms, you need to ask the question: What is the velocity and the acceleration of point A as seen by the observer?