I have an assembly of different material parts. I wanted to know the moment of inertia about a particular axis. I got to a point where I get an output coordinate system and when I click 'Mass Properties' in the 'Evaluate' tab, I get a list of the moments of inertia. But, in that list, it says 'Moments of Inertia about the center of mass' which has units of kilograms-meter^2 and is denoted by 'L'. There is also a list of 'Moments of Inertia about the output coordinate system' which has units of kilogram - meters and is denoted by 'I'. What is the difference between the afore mentioned moments of inertia about different coordinate systems? And why is it denoted with a different letter?

Please reply to this asap. An urgent need!

It's all to do with the parallel axis theorem. I'm no expert, but....the MOI about the centre of mass will be the same as that at the output coordinate system if your Solidworks origin/planes/etc (i.e. the output coordinate system) lies at the centre of mass. The parallel axis theorem is used to determine the inertias at the offset distance (this is the distance between the otuput coordinate system and the centre of mass). This should explain why there can be two different MOI figures 'L' & 'I'.

Best thing to do with these things is always to make a simple model (e.g. a cylinder), with the origin at the centre of mass, and hand calculate the mass moment of inertia. Then check that Solidworks gives you a result you understand. Then offset the simple model from the origin and see what SW gives you. Then hand calculate that setup using parallel axis theorem. No good, I know, if it's URGENT but good to do nonetheless.

You really identified the answer yourself when you asked the question "...

What is the difference between the afore mentioned moments of inertia about different coordinate systems?...". It's because of the different coordinate systems.Hope that didn't turn into a lecture ...