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Formulae for moments of inertia

The list that follows gives the more important moments of inertia for some common simply shaped objects.

(a) Uniform thin rod about one end

Moment of inertia (I) = mL2/3

(b) Uniform thin rod about the middle

Moment of inertia (I) = mL2/12

(c) Circular disc about the centre

Moment of inertia (I) = mr2/2


(d) Cylinder about the axis of symmetry:

(i) solid cylinder

Moment of inertia (I) = mr2/2

(ii) hollow cylinder

Moment of inertia (I) = mr2



(e) Sphere about a diameter

Moment of inertia (I) = 2mr2/5




(f) a ring of negligible width about the centre

Moment of inertia (I) = mr2
 
 
 
© Keith Gibbs 2013