# Homework Help: What does it mean to find the centroid of a shape?

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1. Feb 6, 2016

### CivilSigma

Hello,

I am currently studying how to find the centroid of shapes. And I understand that to find the location of the centroid, we must analyze the distribution of the mass over the x and y axis (i.e calculating Qx and Qy).

However what baffles me is that, given an L shaped beam, the centroid does not necessary need to lie on the mass itself? I thought the centroid was the location where all the mass is concentrated.

How does it make sense that , say the force of gravity, acts outside the shape?

Thank you !

2. Feb 6, 2016

### SteamKing

Staff Emeritus
Yep, for some shapes, the centroid will lie outside the boundaries of the shape.

The centroid is not the point where all the mass is concentrated; it is the point through which all the resultant forces of gravity acting on each particle will act.
The centroid can be thought of as a "balance point" for the object.

http://www.iitg.ernet.in/rkbc/me101/Presentation/L16-18.pdf

3. Feb 6, 2016

### CivilSigma

Thank you very much for the attached presentation! It is so well done.