1. ME 221Lecture 161 ME 221 Statics Lecture #16 Section 4.5

2. ME 221Lecture 162 Homework #6 Chapter 4 problems: –10, 11, 18, 24, 39, 42, 43 & 47 –Must use integration methods to solve –Due Monday, October 14

3. ME 221Lecture 163 Quiz #4 Wednesday, October 9

4. ME 221Lecture 164 Last Lecture: Centroids of Areas, Volumes & Lines

5. ME 221Lecture 165 Centroid of Composite Bodies Basic shapes are added together to get the composite centroid –We look these up in Table 4.2 –This table will be supplied on future exams Problems

6. ME 221Lecture 166 Area Centroids This case is representative of line and volume centroids. Divide total area into simple shapes (rectangles, semi-circles) Add up simple shapes x y xcxc ycyc + + = x3x3 y3y3 A3A3 y2y2 x2x2 A2A2 y1y1 x1x1 A1A1

7. ME 221Lecture 167 May Also Use Subtraction x y xcxc ycyc = - y2y2 x2x2 A2A2 y1y1 x1x1 A1A1

8. ME 221Lecture 168 Composite Centroid of an Area Geometric center of the area –Summation of the pieces (holes are negative) –Where:

9. ME 221Lecture 169 Composite Centroid of a Volume Geometric center of the volume –Average of the first moment over entire volume –Where:

10. ME 221Lecture 1610 Examples