Principles of Dairy Machine Design

Module 1. Statics and dynamics

Lesson 5
SOLVING NUMERICAL

5.1 Problem

Find the moment of inertia of a hollow rectangular section about its Centre of gravity, if the external dimensions are breadth 6 cm, depth 8 cm and internal dimension are breadth 3 cm and depth 4 cm respectively.

Sol.

Outer breadth b = 6cm

Inner breadth b₁ = 3cm

Outer depth d = 8cm

Inner depth d₁ = 4cm

Using the relation

Fig. 5.1

= 256-16 = 240 cm⁴

5.2 Problem

Find the M.I of rectangular section shown in fig. about faces

AB & BC

b = 4cm

d = 6cm

M.I about AB

Fig. 5.2

M.I of the section about an axis through its C.G and parallel to x – x axis