Does Moment of Inertia Determine Mass?

[preluderacer]

Homework Statement

If two objects have the same moment of inertia, they must have the same mass.

The Attempt at a Solution

I think it's false but I can't figure out why.

 

[Mindscrape]

Take a disc and a hoop.

Idisc=MR^2/2
Ihoop=MR^2

I give a disc a radius of 1m, mass of 2kg. I give the hoop a mass of 1kg, radius 1m. The inertias are the same, the masses are not. Just one example of many.

If, on the other hand, two of the same type (density and shape) objects have the same moment of inertia then they ought to have the same mass.

 

[preluderacer]

thanks a lot! i get it now