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:
A hammer is balanced on a finger with two different arrangements. For which arrangement – A or B – is the rotational inertia (I) about the axis the greatest?
 



 

The amount of mass present in a rotating object will affect the rotational inertia of that object. Both of these  objects have the same mass. But the manner in which the mass is distributed within the object is different for the two situations. And the distribution of mass is equally important in determining the rotational inertia of the object. The further the mass is distributed from the axis of rotation, the greater that the rotational inertia will be. The rotational axis is located at the fingertip upon which the hammer is resting. For a hammer, the majority of mass is concentrated in the head of the hammer that is attached to the handle. So when the hammer head is placed on the fingertip, the heaviest part of the hammer is close to the axis of rotation. On the other hand, when the handle is placed upon the fingertip, the heaviest part of the hammer is located far from the axis of rotation. Use this information to determine which situation has the greatest rotational inertia.

 

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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