Final answer:
The moment of inertia about the center of mass axis affects the moment of inertia about any other axis parallel to the C.O.M. axis. The parallel axis theorem can be used to calculate the moment of inertia about a new axis. The new axis must be parallel to the C.O.M. axis for the parallel axis theorem to apply.
Step-by-step explanation:
The moment of inertia about the center of mass axis affects the moment of inertia about any other axis parallel to the C.O.M. axis. When calculating the moment of inertia about a new axis, the parallel axis theorem can be used. This theorem states that the moment of inertia about the new axis is equal to the moment of inertia about the center of the mass axis plus the product of the mass and the square of the distance between the two axes.
The condition that the new axis must be parallel to the C.O.M. axis is because the parallel axis theorem applies specifically to parallel axes. It does not hold for axes that are not parallel. This is because the derivation of the parallel axis theorem assumes that the object is symmetric and that the distance between the axes is constant.