# Homework Help: Disc And Center Of Mass

1. Aug 13, 2015

### Ujjawal Kumar

Hi New member here!
1. The problem statement, all variables and given/known data

In the figure one-fourth part of a uniform disc of radius R is shown. The distance of the center of mass of this object from center ‘O’ is ……………………….

Given: For a semi-circular disc with origin of co- ordinate system at the center of circle, the coordinate of its center of mass is (0,4R/3π ).

(Solve this problem without using calculus)
3. The attempt at a solution
I tried for hours but could not find a solution without using calculus.

Last edited: Aug 13, 2015
2. Aug 13, 2015

### BvU

Hello Ujjawal, welcome to PF !

A challenging exercise. Think symmetry and folding:
The given information tells you the center of mass shifts from 0 to $(0,{4\pi \over 3r})$ when you fold a full circle in half.

Is that enough of a hint ?

3. Aug 14, 2015

### Ujjawal Kumar

Yes, and thank you BvU!

4. Aug 15, 2015

### AR1399

This problem actually took me quite some time to figure.......thnx for the hint BvU!

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