I have a disk parallel to the floor rotating about an axis perpindicular to the floor, going through the center of the disk.(adsbygoogle = window.adsbygoogle || []).push({});

Its moment of inertia is [tex]I=\frac{1}{2}mR^2[/tex]

I also have a ring (which I will forbear to describe. A picture is worth a thousand words [or 30-ish, in this case], so please see attatchment) with intertia [tex]I=\frac{1}{2}m(R_1^2+R_2^2)[/tex]

All fine and dandy. But when I place one on top of the other (still rotating about the same axis), to find the moment of inertia, do I just add their individual moments? Or something else?

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Moment of inertia (compound object)

**Physics Forums | Science Articles, Homework Help, Discussion**