- #1

Ja4Coltrane

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I'm trying to show that the moment of inertia for a sphere is (2/5)MR^2

So I started with I=(integral)(r^2)(dm)

then P=dm/dv=dm/(4pi(r^2)dr)

so dm=(4)(pi)(r^2)(P)(dr)

so I substituted into the original equation, removed constants from the integral, and substituted P for M/V=(3M/(4(pi)(R^3)))

I=12pi(M)/(4(pi)r^3)[integral]r^4 (dr)

I=(3/5)MR^2 which is wrong!

(sorry about the lack of pretty math writing)

Thanks for any help, and by the way, I'm only a high school student so my calculus knowledge is very limited (in fact, the only reason I know what integration is is because of my physics class).