Moment of inertia of a uniform solid sphere

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SUMMARY

The moment of inertia (I) of a uniform solid sphere is calculated using thin cylindrical shells, resulting in the formula (2/5)MR². While thin spherical shells can also be utilized, they yield the same moment of inertia. The discussion clarifies that both methods are valid, but cylindrical shells are preferred due to their straightforward derivation process. The confusion arises from the derivation steps, which favor cylindrical shells for clarity and ease of calculation.

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  • Understanding of moment of inertia concepts
  • Familiarity with calculus and integration techniques
  • Knowledge of solid geometry, specifically spheres and cylinders
  • Experience with physical principles of rotational motion
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  • Study the derivation of moment of inertia using thin cylindrical shells
  • Explore the application of spherical shells in calculating moment of inertia
  • Learn about the physical significance of moment of inertia in rotational dynamics
  • Investigate the differences between various methods of calculating moment of inertia for different shapes
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Physics students, mechanical engineers, and anyone studying rotational dynamics or solid mechanics will benefit from this discussion.

david456103
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For calculating I of a uniform solid sphere, why can't we use thin spherical shells? When I try to use spherical shells I get (3/5)MR^2. Every single derivation uses thin cylindrical shells and end up with the correct expression((2/5)MR^2) but they never explain why it is correct to use cylindrical shells and not spherical shells.
Thanks!
 
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You certainly can get there via spherical shells, but it produces the same answer: 2/5.
What do you get for the MI of the shell?
 

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