# A question about Centre of Gravity

clevermartin

## Homework Statement

A uniform disc A of radius 2m is cut as shown in the figure. The cut out is also a disc of radius 1m. O is the centre of gravity of disc A before cutting and O' is its centre of gravity after cutting. Find the distance between O and O'

## The Attempt at a Solution

I know how to find the CG of disc A and the CG of the new disc respectively..
But i don't know how to find out the CG of the newly cut disc A...
I don't know what approach should I use in this question

#### Attachments

• cg.jpg
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clevermartin

e(ho0n3

First question: How do you find the center of gravity of an object?

Mentor
I know how to find the CG of disc A and the CG of the new disc respectively..
But i don't know how to find out the CG of the newly cut disc A...
I don't know what approach should I use in this question
I assume you can find the center of mass of two overlapping solid discs. Hint: What kind of disc would you have to add to disc A to get a hole of the right size and placement? Hint2: A + -B = A - B (It's a mathematical trick!)

clevermartin
I assume you can find the center of mass of two overlapping solid discs. Hint: What kind of disc would you have to add to disc A to get a hole of the right size and placement? Hint2: A + -B = A - B (It's a mathematical trick!)

I know how to do it now~ Thanks a lot