Math experts please help

[bonehelm]

Okay i'm stuck on this question: I know that the moment of inertia for a sphere is 0.4MR^2.

A two layer model of Mars, consisting of an iron core of radius r>R whose density is 7.9E3 kg/m^3, surrounded by a rocky mantle of density 3.2E3 kg/m^3.

Find an expression for I/(MR^2) as a function of r/R (Express the mass M of the planet in terms of the density of the two layers). Verify that:

a) The expression is dimensionally correct, and
b) The expression is correct for the extreme cases r = 0 and r/R = 1.

thanks a lot, I asked a lot of classmates and no one seem to know the answer.

 

[Crysalis]

chankama is your man

 

[Mr. Switch]

Chankama to the rescue!

 

[bobojuice]

wtf....

**** math sucks.

 

[idiotec]

chankama is your man

 

[ncjimn]

I would've done this myself *maybe*

but yeah, why me when google can help:

Source: http://hyperphysics.phy-astr.gsu.edu/hbase/isph.html

 

[Mr. Switch]

HOLy ****ingskhit akjesxus chrtsit vukinfslksbeers JUDT











GGGGGAHNH JUST COOL ITS HOWOULD YOU~!?!?!1

 

[Crysalis]

uhh..... what?

 

[COD2_fanatic]

what class would you EVER take this kind of stuff in? JESUS i hope i dont have to take anything like that, i'm bad enough with algebra the way it is (but good with Geometry (10th grade if you want to know))

 

[ncjimn]

what class would you EVER take this kind of stuff in? JESUS i hope i dont have to take anything like that, i'm bad enough with algebra the way it is (but good with Geometry (10th grade if you want to know))

That integral isn't that bad, but I guess comparing to 10th grade math it does look kind of intimidating.

Hopefully you'll get to this (the fun stuff) in calculus, you can do AP in high school!

fun fun fun!