Advanced/Notes 7.8
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Transcript of Advanced/Notes 7.8
![Page 1: Advanced/Notes 7.8](https://reader035.fdocuments.us/reader035/viewer/2022081512/55413275550346fb668b459c/html5/thumbnails/1.jpg)
Center of MassSection 7.8
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Center of Mass
• Why do we need to calculate the center of mass?
• How do we calculate the center of mass?
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Center of Mass
• For all of our motion problems we have treated every object like a point mass
• We have also said that the only motion has been translational (*)
• Is this legit?
![Page 4: Advanced/Notes 7.8](https://reader035.fdocuments.us/reader035/viewer/2022081512/55413275550346fb668b459c/html5/thumbnails/4.jpg)
Diver
• Part A, the motion is purely translational
• Part A has translation and rotation
• Note that one point moves in a parabola, which is how we treated it
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Tossing a wrench
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Center of Mass
• General Motion of an object =• Sum of translational motion of the CM• Plus rotational, vibrational, etc.. Motion about the CM
![Page 8: Advanced/Notes 7.8](https://reader035.fdocuments.us/reader035/viewer/2022081512/55413275550346fb668b459c/html5/thumbnails/8.jpg)
Calculating CM
• For two particles
• M is total mass
• Note where you are measuring from
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Center of Gravity
• Center of gravity: the point where the gravitational force can be considered to act
• If you hung something at any point other than the center of gravity, it would pivot
• Usually the same as the center of mass
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Center of Mass
• Found experimentally by suspending objects
• Can be out side the object
• Doughnut’s is in the center of the hole
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Example
• Three people of roughly the same equal mass m on a lightweight air filled banana boat sit along the x axis of positions xA = 1.0 m, xB = 5.0 m and xC = 6.0 m, measured from the left hand position.
• Find the position of the CM. Ignore the mass of the boat
![Page 12: Advanced/Notes 7.8](https://reader035.fdocuments.us/reader035/viewer/2022081512/55413275550346fb668b459c/html5/thumbnails/12.jpg)
Homework
• Read Section 7.7• Do Problems # 46 - 50, Page 189