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Fundamentals

The rotational inertia of an object or system of objects refers to the general resistance the object has to a change in its rotational state. The amount of rotational inertia an object possesses depends on how much mass it has and how that mass is distributed relative to the axis of rotation.

 

There are two similar versions of this question. Here is one of the versions:

Version 1:
Two identical solid disks are arranged along a solid bar at different locations. For which arrangement – A or B – is the rotational inertia (I) about the vertical axis the greatest?


 

How to Think About This Situation:

The amount of mass present in a rotational system will affect the rotational inertia of that system. Both of these  systems have the same mass. But the manner in which the mass is distributed within the system is different for the two situations. And the distribution of mass is equally important in determining the rotational inertia of the system. The further the mass is distributed from the axis of rotation, the greater that the rotational inertia will be. So inspect the two systems and determine in which case is the mass furthest from the rotational axis (dashed line). 

 

Try these links to The Physics Classroom Tutorial for more help with understanding the concept of rotational inertia:

​Sorry. We hope to add resources in the future.
 

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