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||<:30%>[:PiraScheme#Mechanics: Table of Mechanics Demonstration]||<:30%>[:MEEquipmentList: List of Mechanics Equipment & Supplies]||<:30%>[:Demonstrations:Lecture Demonstrations]|| ||<:30%>[[PiraScheme#Mechanics| Table of Mechanics Demonstration]]||<:30%>[[MEEquipmentList| List of Mechanics Equipment & Supplies]]||<:30%>[[Demonstrations|Lecture Demonstrations]]||
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 [:RigidBodies#FindingCofG: 1J10. Statistics of Rigid Bodies, Finding the Center of Gravity]  [[RigidBodies#FindingCofG| 1J10. Statistics of Rigid Bodies, Finding the Center of Gravity]]
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 * '''Cabinet:''' [:MechanicsCabinet:Mechanic (ME)]
 * '''Bay:''' [:MechanicsCabinetBayA6:(A6)]
 * '''Cabinet:''' [[MechanicsCabinet|Mechanic (ME)]]
 * '''Bay:''' [[MechanicsCabinetBayA6|(A6)]]
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 * [https://www.youtube.com/user/LectureDemostrations/videos?view=1 Lecture Demonstration's Youtube Channel]  * [[https://www.youtube.com/user/LectureDemostrations/videos?view=1|Lecture Demonstration's Youtube Channel]]
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 * [https://en.wikipedia.org/wiki/Center_of_mass Center of Gravity - Wikipedia]  * [[https://en.wikipedia.org/wiki/Center_of_mass|Center of Gravity - Wikipedia]]
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[:Instructional:Home] [[Instructional|Home]]

Table of Mechanics Demonstration

List of Mechanics Equipment & Supplies

Lecture Demonstrations

Hanging Irregular-Shaped Board, 1J10.12

Topic and Concept:

Location:

IrregBoard04-400.jpg

Abstract:

Suspend an irregular-shaped board from several points, and use a plumb bob to find the center of gravity.

Equipment

Location

ID Number

Irregular-Shaped Boards

ME, Bay6 , Shelf #4

Plumb Bob

ME, Bay A6, Shelf #4

Rod Stand

Rod and Clamp Cabinet

Important Setup Notes:

  • N/A

Setup and Procedure:

  1. Instead of a weighted rod stand as pictured, a rod clamped to the lecture bench works well too.
  2. Make sure there are two smaller rods cantilevered off the vertical rod.
  3. From each eyebolt, suspend the board, and hang the plumb bob from the higher rod.
  4. For each suspension point, trace a line along the string of the plumb bob using a dry-erase marker.
  5. Draw a point on the location where all of these lines intersect. This is the center of gravity.

Cautions, Warnings, or Safety Concerns:

  • N/A

Discussion:

The orientation of the board while suspended from the rod is determined by the collective effect of gravity on each mass element of the board. For each point of mass in the board not in the center of mass, there will be a torque on the board due to gravity. The equilibrium orientation of the board is the configuration of zero torque. The center of mass will always be located under the suspension point (on the line traced by the plumb bob). The point where all these lines intersect is the point where the sum of the position vectors for every mass element, weighted by mass, is zero. I.e. where Σi ri * mi = 0.

IrregBoard01-250.jpg

IrregBoard02-250.jpg

IrregBoard03-250.jpg

PlumbBob01-250.jpg

IrregBoard05-250.jpg

IrregBoard06-250.jpg

IrregBoard07-250.jpg

Videos:

References:

Home

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