Calculating Center of Mass: Pendant Sector with Holes

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Homework Help Overview

The problem involves calculating the center of mass of a pendant shaped like a sector of a circle, which has several small holes cut out. The pendant is modeled as a uniform lamina, and the dimensions and positions of the holes are specified.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to calculate the center of mass using moments about a point, but expresses confusion regarding the discrepancy between their calculated value and the expected answer. Some participants question the accuracy of the diagram and the center of mass of the sector itself.

Discussion Status

The discussion is ongoing, with participants seeking clarification on the diagram and the center of mass of the sector. There is no explicit consensus yet, but the original poster has acknowledged an error in their initial post regarding the center of mass of the sector.

Contextual Notes

Participants note that the original diagram was unclear, which may affect the understanding of the problem setup. The original poster has made edits to clarify the center of mass of the sector.

phospho
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The diagram shows a pendant in the shape of a sector of a circle with center A. The radius is 4 cm and the angle at A is 0.4 radians. Three small holes of radius 0.1 cm, 0.2cm and 0.3 cm are cut away. The diameters of the holes lie along the axis of symmetry and their centers are 1, 2 and 3 cm respectively from A. The pendant can be modeled as a uniform lamina. Find the distance of the center of mass of the pendant from A. Moments about A (y = 0 due to symmetry)

[itex]x = \frac{(0.5\times4^2\times0.4)\times(\frac{2\times4\times(sin(0.2))}{0.6}) - (0.1^2\pi\times(1)) - (0.2^2\pi\times(2))-(0.3^2\pi\times(3))}{(0.5\times4^2\times0.4) - (0.1^2\pi) - (0.2^2\pi) - (0.3^2\pi)} <br /> => x = 2.66...[/itex]
However the answer is 2.47 :s
 
Last edited:
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diagram?
 
Where's the center of mass of the sector itself?
 
Anva0.png
The diagram was rather rubbish so I didn't include it (it's pretty much exactly like this, just the circles centers are in the line of symmetry).

I've edited my original post to include the center of mass of the sector - I just copied it wrong.
 

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