12 RODS OF LENGTH L MAKE A CUBE. WHAT IS THE MOMENT OF INERTIA OF THE CUBE ABOUT ITS FACE DIAGONAL?

Let, the cube is made by 12 rods, we know that M.I. of each rod is ML²/2 ,

   now let, talking about face of a cube at 2D i.e. a square ,

    so its diagonal(or its length)= √2L

    for square. MI is = M(√2L)²/2

                            = 2ML²/2

                            = ML² (IT IS FOR 4 ROD) SO IT CAN BE :

                             =3ML²(FOR 12 RODS)

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