Question
what is the moment of inertia of a cube about its diagonal?
Joshi sir comment
Moment of inertia of a cube about a line perpendicular toits one face and passing through its centre is ma2/6so about diagonal inertia = l2Ix+m2Iy+n2Iz = (l2+m2+n2)Ix (here Ix=Iy=Iz)= Ix = ma2/6l,m,n are direction cosines of three lines passing througecentre of cube and perpendicular to each other