Question

pendulum of rod and connected disc when disc is rotating

Answer 1

1. The problem statement, all variables and given/known data
Find the moment of intertia of a pendulum, consisting of a disc free to spin attached to a rod that is hinged at one end.

2. Relevant equations
Moment of intertia of rod hinged at end = (1/3)Ml2
Moment of intertia of disc = (1/2)mR2 + ml2

3. The attempt at a solution
Why does the answer disregard the partmoment of intertia of the disc (1/2)mR2that is spinning on its own axis, and only taking into account the ml2?