The easiest derivation of rod's moment of inertia?

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SUMMARY

The derivation of the rod's moment of inertia is expressed by the formula I = ml²/12. The discussion highlights the integration method, specifically using I = ∫ r² dm, where 'dm' represents an infinitesimal mass element at a distance 'r' from the center of mass. The mass element is calculated as dm = M/L * dr, where M is the total mass and L is the length of the rod. This approach simplifies the understanding of the moment of inertia for a uniform rod.

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  • Understanding of basic calculus, specifically integration techniques.
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  • Knowledge of mass distribution along a rod.
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Students in physics, particularly those studying mechanics, as well as educators seeking to explain the concept of moment of inertia in a clear and accessible manner.

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Homework Statement


Derive the formula for rod's moment of inertia: I = ml2/12


Homework Equations


I = ml2/12


The Attempt at a Solution


The only one derivation I know of is dividing the rod into two parts and then integrating from 0 to l/2. However' I'd love to know if there's some easier (or more "natural"?) way to do it? Or, if not, maybe you know some website where it's explained as if I were five so that I can get the grasp of it? Because looking at bare integrals, I don't quite know what I'm calculating.
 
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I think the easiest way would be to just do the integral.

I= ∫ r2 dm

If you consider a small infinitesimal piece at a distance 'dr' from the center of mass of the rod, the mass of this piece will be dm.

Then you just use the fact that mass = mass per unit length * distance i.e. dm = M/L * dr
 
I see. Thanks :)
 

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