Let the mass moment of inertia of differential mass about 0 – 0 axis be dm as shown in Fig. P-8.1.

Mass Moment of Inertia Introduction” = C

If it is perpendicular to plane of rotation of centre of mass, then it can be written as,

dI = r2 dm


I = 2 dm


I = Mass Moment of Inertia

Keeping the mass density, p as constant, then we get-

dm = p dV


dV = Element of Volume

Hence, from Fig. P-8.1,

I = 2p dV

  = P2 dV

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