Moment of inertia of ring about its center:
ICM=MR2Using the parallel axis theorem:
The parallel axis theorem says: If you know the moment of inertia of an object about its center (
ICM ), then the moment of inertia about a parallel axis a distance
R away is:
I=ICM+MR2For a thin circular ring, this axis through the edge is a distance
R from the center, so:
I=MR2+MR2=2MR2So,
MR2=‌Finding the moment of inertia about the diameter:
The moment of inertia of a ring about its diameter is:
Id=‌Substituting from equation (i):
Replace
MR2 with
‌:Id=‌=‌