# Mechanics - centre of mass lamina

1. May 24, 2010

### kolomsg

hi, I'm stuck and I cant seem to find a simple solution to questions regarding how to find the centre of mass of a lamina.

for example:
A uniform lamina with mass/unit area 0.12grams/cm2 consists of a square of
side 80cm, with one corner at the origin O(0, 0) and other corners at B(80, 0),
C(80, 80) and D(0, 80). A triangle of material has been removed from one corner
by cutting a straight line from E(50, 0) to F(80, 40), and a particle of mass 0.5kg
is attached at C. Find the coordinates of the centre of mass.
If anyone could help me, that'd be much appreciated. thanks

2. May 24, 2010

### tiny-tim

Welcome to PF!

Hi kolomsg! Welcome to PF!

Do you know how to find the coordinates of the centre of mass of several bodies, given that you know the coordinates of the centre of mass of each?

Apply that to the square, the triangle, and the particle, but with the triangle having negative mass!

3. May 26, 2010

### kolomsg

hi, thanks a lot. it helped!