$A$ wire of mass $M$ is bent into a circular shape of radius $R$. What is the moment of inertia about its diameter?

Find the moment of inertia of the system of particles about the axis $OA$ passing through point $O$.

Four identical uniform solid spheres,each of same mass '$M$' and radius '$R$',are placed touching each other as shown in the figure with centers $A, B, C, D$. If $I_{A}, I_{B}, I_{C}, I_{D}$ are the moments of inertia of these spheres respectively about an axis passing through their centers and perpendicular to the plane,then:

$A$ ring,a solid sphere,and a disc have the same mass and radius. Which of them has the largest moment of inertia?

Three identical rods,each of length $l$ and mass $M$,are joined to form a rigid equilateral triangle. Its radius of gyration about an axis passing through a corner and perpendicular to the plane of the triangle is

Two discs,one of density $7.2 \, g/cm^3$ and the other of density $8.9 \, g/cm^3$,have the same mass and thickness. What is the ratio of their moments of inertia?