Moment of inertia depends on the axis
The mistake
Treating I as a fixed property of the object.
Why it feels right
Mass is a single number, so rotational inertia seems like one too.
How to catch it
You reused I from a table without matching the axis.
The first principle
I depends on how mass is distributed about the chosen axis. Use the parallel-axis theorem I = I_cm + Md² to shift axes.
worked mini-example
A rod spun about its center versus its end — same I?
Common wrong move
Yes, it's the same rod.
Correct
No: I_end = ML²/3 is four times I_center = ML²/12.
Test the repair ROT-03 · transfer
Make a fresh prediction before referring to the worked example.