How do you calculate Center of mass

[okgo]

Homework Statement

I'm confused about how to find the center of mass
http://www.screencast.com/users/ntrinh3/folders/Jing/media/a9773d23-38f1-4d28-a6f8-3b681d42d4c2

and

http://www.screencast.com/users/ntrinh3/folders/Jing/media/bfb40c40-0068-41e8-ac83-2146e1df3330

Homework Equations

So the equation my professor gives Cm=sum of MR/sum of masses

The Attempt at a Solution

Where exactly is this R reference point?

 

[rock.freak667]

You just pick a point, for example if you pick your reference as the 2kg mass, then your COM will be measured from there.

 

[okgo]

oh so that's it.

How about if they just give you the x-coordinate in a system? exe:

http://www.screencast.com/users/ntrinh3/folders/Jing/media/010db89d-7781-4262-aa79-57eaf706730f

do you just add all of the x-coordinates and divide by how many points?

 

[rock.freak667]

MX=m₁x₁+m₂x₂+m₃x₃+...

the 'x's are measured relative to wherever you take your reference point as.