ME 221 Statics
Lecture #15
Section 4.3
ME 221
Lecture 15
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Homework #5
• Chapter 3 problems:
– 48, 51, 55, 61, 62, 65, 71, 72 & 75
– May use MathCAD, etc. to solve
– Due today
ME 221
Lecture 15
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Homework #6
• Chapter 4 problems:
– 10, 11, 18, 24, 39, 42, 43 & 47
– Must use integration methods to solve
– Due Monday, October 14
ME 221
Lecture 15
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Quiz #4
• Wednesday, October 9
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Last Lecture:
• The concepts of distributed loads, centroids
and center of gravity were presented.
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Centroid of an Area
• Geometric center of the area
– Average of the first moment over the entire area
1
xc   xdA
AA
– Where:
1
yc   ydA
AA
A   dA
A
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Centroid of an Area
• Is then defined as an integral over the area.
• Integration of areas may be accomplished
by the use of either single integrals or
double integrals.
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Centroid of a Volume
• Geometric center of the volume
– Average of the first moment over entire volume
1
xc   xdV
VV
1
yc   ydA
AA
– In vector notation:
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zc   zdV
VV
1
rc   rdV
VV
8
Examples
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