Question

Two thin disks are attached as shown to the right. The angle θ = 30.8°, and the masses and radii of the disks are listed in the table below.

Answer 1

I believe that we can take these two disks as point masses with mass concentrated at their centers

we then can use I = m r^2 for each and add together
for the larger disk r = 0.123m
flor the smaller we ndde the distance from P to its center

that distance is the third side of the triangle wth sides 0.123m and 0.175m
and the angle between these sides is 149.2°
then using Law of Cosines
r^2 = 0.123^2 + 0.175^2 - 2(0.123)(0.175)(cos149.2) = 0.0827
r = 0.2875
so
I = 0.521kg*(0.123m)^2 + 0.475kg*(0.2875m)2 = 0.04714kg*m^2