1. CE 201- Statics
Chapter 9 – Lecture 2

2. COMPOSITE BODIES
Composite body consists of simpler bodies connected together (triangle, rectangle, ….)
Composite body can be sectioned into its composite parts
Center of gravity of the composite body can be determined without integration, if weight and center of gravity of each part is known
Each part can be treated a discrete particle and use:
x = ( x W) /  WR
y = ( y W) /  WR
z = ( z W) /  WR

3. COMPOSITE BODIES
When the body has a constant density or specific weight, the center of gravity coincides with the centroid of the body
The centroid of line, area, and volume can be found by replacing W with L, A, and V (respectively) in the equations above:
x = ( x L) /  L
y = ( y L) /  L
z = ( z L) /  L
x = ( x A) /  A
y = ( y A) /  A
z = ( z A) /  A
x = ( x V) /  V
y = ( y V) /  V
z = ( z V) /  V

4. Procedure for Analysis
Divide composite body into simpler shapes
If the body has a hole or geometric region having no weight, then consider the body without the hole and the hole as an additional composite part having negative weight or size.
Determine x, y, and z of the center of gravity or centroid of each part
Determine x, y, and z of the whole body