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Document Title
Fundamentals of Stress and Vibration Chapter Title
[A Practical guide for aspiring Designers / Analysts] 2. Engineering Mechanics
The principal inertias have maximum, minimum and intermediate values for inertia for a given
component. That is, if I , I and I are the maximum, intermediate and minimum values of
3
2
1
principal inertias respectively, then, I > I > I .
3
1
2
For spinning objects, the inertia directions I and I that is, the maximum and minimum inertia
1
3
directions, become the axes of stability.
Example 1: compute the 3 principal inertias for a cuboid as shown in [Fig 2.43] and write the
inertia tensor.
[Fig 2.43: 3 principal inertia axes of a cuboid]
Solution: The inertia about each axis can be found by the typical procedure followed earlier. Here,
the inertia about the principal axis is computed along with the inertia about the axis of each section.
Page 56 QP No. SSC/Q4401, Version 1.0, NSQF Level 7, Compliant with Aero and Auto Industries,
