Moments of Inertia for a Cylinder and Disk

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SUMMARY

The moment of inertia for a cylinder is defined as I = (1/4)MR² + (1/12)ML² when calculated about an axis through its center, while for a disk, it is I = (1/2)MR². The confusion arises from the choice of the axis of rotation, which significantly affects the moment of inertia. Correct application of these formulas is crucial for accurate calculations in physics problems. The discussion highlights the importance of understanding the axis about which the moment of inertia is calculated.

PREREQUISITES
  • Understanding of moment of inertia concepts
  • Familiarity with rotational dynamics
  • Knowledge of the parallel axis theorem
  • Basic algebra for manipulating equations
NEXT STEPS
  • Study the parallel axis theorem for calculating moments of inertia
  • Learn about the moment of inertia for various shapes, including spheres and rods
  • Explore applications of moment of inertia in rotational motion problems
  • Review examples of calculating moment of inertia about different axes
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Students of physics, educators teaching mechanics, and anyone involved in engineering or physical sciences who needs to understand the principles of rotational motion and moment of inertia calculations.

johnhuntsman
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What are they? I have some poeple telling me that for a cylinder it's I = (1/4)MR2 + (1/12)ML2 and that for a disk it's the same. Other people have told me that it's I = (1/2)MR2 for a disk and that it's the same for a cylinder. In the past I've used the former and have gotten the right answers on my homework but I used the same equation for a question I'm stuck on and got the incorrect answer. I just want some clarification on this, I'd really appreciate it.
 
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The moment of inertia of an object depends on the choice of axis that it rotates about.
http://www.tutorvista.com/content/physics/physics-iii/rigid-body/moment-inertia-rod.php
 
TSny said:
The moment of inertia of an object depends on the choice of axis that it rotates about.
http://www.tutorvista.com/content/physics/physics-iii/rigid-body/moment-inertia-rod.php

Ah. I didn't see that I was using the equation for a cylinder about a diameter. Thanks. I appreciate it : D
 

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