Finding Rotational Inertia with Thin Rod: Explanation and Example

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SUMMARY

The discussion focuses on calculating the rotational inertia of a thin rod using the equation I = 1/12 M L², applicable when the rotation axis is at the center. The user initially misapplied the equation by doubling the distance, resulting in an incorrect value of 5/3Md². The correct approach involves using the parallel axis theorem to find the rotational inertia about the end of the rod, leading to the correct answer of 8/3Md².

PREREQUISITES
  • Understanding of rotational inertia and its significance in physics.
  • Familiarity with the equation I = 1/12 M L² for thin rods.
  • Knowledge of the parallel axis theorem and its application.
  • Basic algebra skills for manipulating equations.
NEXT STEPS
  • Study the parallel axis theorem in detail to understand its applications.
  • Practice calculating rotational inertia for various shapes and axes of rotation.
  • Explore the implications of rotational inertia in real-world physics problems.
  • Learn about the differences in rotational inertia calculations for solid versus hollow objects.
USEFUL FOR

Physics students, educators, and anyone interested in mechanics and rotational dynamics will benefit from this discussion.

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Homework Statement


How do I find Rotational inertia of this?http://yfrog.com/e4asdfasdfasdfj. Assumed thin rod (ignore r).

Homework Equations


I=1/12 M L2

The Attempt at a Solution


Cause that equation applies if the rotation axis is at the center, so I doubled d (and got like (2d)2 and (4d)2) and used the equation, but I ended up with something like 5/3Md2, but the answer at the back says its 8/3Md2.
 
Physics news on Phys.org
If you know the rotational inertia about the center of mass, use the parallel axis theorem to find the rotational inertia about the end.
 

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