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## Homework Statement

I need to know why my derivation does not work. I am attempting to derive I=2/5 mR^2

## Homework Equations

I have seen people derive it using disks but my question is why do the shells not work? Where in my set up did I go wrong??? Thanks

## The Attempt at a Solution

I am attempting to use shells to do this.

integral(r^2dm)=I

Ro=p=m/v so pdv=dm

dv=4(pi)r^2dr

moment of inertia (I) =definite integral from r=0 to r=R (4p(pi)r^4dr)

When I solve this integral it becomes (3/5)mR^2 and not (2/5) mR^2