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- The object's physical dimensions are much smaller than its separation from the chosen axis of rotation AND the object's specific rotational state is not of interest.
- The object will clearly not rotate about its center of mass as a result of the interactions in the problem.
The first of these two possibilities guarantees that the moment of inertia of the object about the specified axis is completely dominated by Md2 term in the parallel axis theorem. The second possibility implies that the angular momentum of the object about the specified axis can be found using no object variables other than the mass.
Examples of problems in rotational dynamics where one or more constituents of a system are treated as point particles are:
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