Because I = m * r^2 grows with the square of radius, pulling mass inward shrinks the moment of inertia and makes the body easier to spin, like a skater drawing in their arms. The trend is exact only for the stated point mass and radius in the ideal rigid-body model. Real systems add distributed mass, axis choice, friction, flexing, calibration, and measurement uncertainty.
The same mass near the axis has a smaller rotational ledger. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Closer mass has much less inertia
With the same 2 kilogram mass at radius 1 meter, the inertia is only 2 kilogram meter squared.
I=2×12=2kgm2
Radius controls how hard spin is to change
The inertia drops from 18 to 2 when the mass moves inward.