# Question #89cc5

##### 1 Answer

We know that the moment of inertia

#color(blue)(I=1/2MR^2.......................[1])#

Now

where

Hence equation [1] becomes

#color(green)(I=1/2Mxx((3M)/(4pidrho))^(2/3).......................[2])#

Now if

#color(red)(Iprop1/rho^(2/3).......................[3])#

If the moment of inertia of first disk of density **the ratio of moment of inertia** of two disks is given by

#color(blue)(I_1/I_2=(rho_2/rho_1)^(2/3)=(8.9/7.2)^(2/3)~~1.15)#