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# Moment, Center of Mass, Centroids

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Author: Richard Enderton
##### Description:

The student should be able to calculate the center of mass of linear and two-dimensional systems of discrete point masses, and apply integrals to finding the center of mass of a planar lamina.

This packet consists of 3 videos and a problem set. The first video shows how to calculate center of mass for linear and two-dimensional systems of discrete masses. The second develops the use of integration to find the center of mass of a planar lamina, and with that, the centroid of a region. The third video walks through some examples.

(more)
Tutorial

## Prerequisites

Students should be able to apply the concept of integration as a summation.

## Moments and Center of Mass - One and Two Dimensional Discrete Mass Systems

This video looks at the terminology and techniques involved with finding center of mass of linear and two-dimensional systems.

## Center of Mass - Planar Laminas

This video develops the integral technique for calculating the center of mass of a planar lamina (and centroid of a region).

## Center of Mass, Centroids - Examples

This video walks through three example of applications of the formulas.

## Problem Set

1. Find the center of mass of the given point masses lying on the x-axis (2.636)

2. Find the center of mass of the given system of point masses (0.581, 3.226)

3. Find the center of mass of the planar lamina of uniform density bounded by (12/5, 3/4)

4. Find the center of mass of the planar lamina of uniform density bounded by (3/2, 22/5)

5. Find the center of mass of the planar lamina of uniform density which is a polygonal region with the vertices

(0,3), (1,3), (1,1),  (3,1), (3,2), (4,2), (4,0), (0,0)    (1.786, 1.071)

6. Find the center of mass of the planar lamina of uniform density which has the region shown (0, 3.167) with x-axis along the bottom of the circles and the y-axis between the circles

7. Find the centroid of the region bounded by (8/15, 8/21)

8. Find the centroid of the polygonal region (trapezoid) with vertices

(0,0), (0,4), (5,4), (9,0)        (3.595,1.810)

## Additional Resources

Paul's Online Notes

Online Physics Lab

Math Open Source

Math Words

Wolfram Alpha

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