# Center of gravity

## Homework Statement

A unifrom disc A of radius 2m is cut as shown in the image. The cut out is also a disc of radius 1m. Find the distance of the two center of gravity before and after the paper disc is cut.

http://crossfacer.com/circle.jpg [Broken]

## Homework Equations

x=m1x1/M+m2x2/M+......

## The Attempt at a Solution

Mass of the disc is proportional to its area.
so mass of disc A=2^2pi=4pi units
mass of disc being cut out=1^2pi=pi units

Let x be the distance between the two centers of gravity.
(4pi-pi)(2-x)=(4pi)(2)-(2+1)(pi)
x=0.333m

This question is quite difficult for me. I don't have much confidence on my answer.:tongue2: May anyone try it? Last edited by a moderator:

Related Introductory Physics Homework Help News on Phys.org
mezarashi
Homework Helper

You assume the homogeneity of the disc, and thus mass is proportional to the area. You know that together, they produce a center of gravity balanced at the center of disc A, and your equations reflect that.

I feel like my answer is not correct . I guess x should be about 0.5.