Final answer:
When mass is concentrated on the outside of a spinning object, the moment of inertia increases. This is because the distance between the mass and the axis of rotation increases, resulting in a larger moment of inertia.
Step-by-step explanation:
The moment of inertia of an object depends on both its mass and the distribution of mass relative to the axis of rotation. When mass is concentrated on the outside of a spinning object, the moment of inertia increases. This is because the distance between the mass and the axis of rotation increases, resulting in a larger moment of inertia.
For example, consider a spinning rod. The moment of inertia of a long rod spun around an axis through one end perpendicular to its length is ML²/3, which is greater than if you spun a point mass M at the location of the center of mass of the rod (at L/2), which would be ML²/4.
The same principle applies to other objects, such as a hoop compared to a disk or a spherical shell compared to a solid sphere. In each case, the moment of inertia is greater when mass is concentrated on the outside.