What is the moment of inertia for a sphere rotating about a tangent axis?

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Homework Help Overview

The discussion revolves around determining the moment of inertia for a solid sphere rotating about an axis that is tangent to its surface. Participants explore the implications of this setup within the context of rotational dynamics.

Discussion Character

  • Conceptual clarification, Assumption checking, Mixed

Approaches and Questions Raised

  • Participants question the definition of a tangent axis and its implications for the axis of rotation. There is a discussion on whether the sphere can be treated as a point particle at a distance from the axis. The parallel axis theorem is mentioned as a potential approach, though some express unfamiliarity with it.

Discussion Status

The discussion is active, with participants seeking clarification on the definition of tangent and exploring the relevance of the parallel axis theorem. While some guidance has been offered regarding the theorem, there is no explicit consensus on the approach to take.

Contextual Notes

Participants note that the assignment does not specifically require finding the moment of inertia around the tangent axis, indicating a potential constraint in the problem's context.

danielatha4
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Can someone please tell me the moment of inertia for a solid sphere rotating about an axis tangent to its surface?
 
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What does tangent to its surface mean? Where is the axis of rotation?
 
The axis of rotation is touching the surface of the sphere at one point. That is the definition of tangent. Can it be treated as a point particle distance R from the axis?
 
Parallel axis theorem?
 
Sorry, never heard of that. It's not the goal of the assignment to figure out the moment of inertia around the axis tangent to the surface, but it would be a useful tool.
 
Well look it up, it is not that difficult. It allows you to use the moment of inertia of a sphere (axis through center) to calculate the moment of inertia somewhere else as long as the other axis is parallel to the axis through the center. And finding the moment of inertia with axis through center is in almost every textbook and on the internet. http://en.wikipedia.org/wiki/Parallel_axis_theorem
 

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