# Acceleration of centre of mass problem

1. Oct 12, 2013

### coldblood

Hi friends,
I have an issue in solving a Acceleration of center of mass problem.

The problem is as:

https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-prn2/q71/s720x720/1395961_1432382973655475_777941089_n.jpg

Attempt:

https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-ash4/q82/s720x720/1381887_1432380636989042_263502974_n.jpg

Friends according to me the answer should be Option (b) but question says the answer is option (a).Please try to help me in this.
I will appreciate the help.

2. Oct 12, 2013

### NihalSh

When you will convert your answer to vector form, the answer would match option (a). Because the vectors include the direction, so minus sign will not be shown. Assuming positive direction to be downwards, then $\vec{R}=-R$

3. Oct 15, 2013

### coldblood

Thanks NihalSh, I got that.
Thank for the help.