# Past Year Exam Question

• October 30th 2012, 05:30 PM
weijing85
Past Year Exam Question
Hi guys,

Anyone know how to solve this?

Two particles A and B, of masses m and 4m respectively, lie on a smooth horizontal surface. Their position vectors with respect to the origin in Cartesian coordinates, are -3i and i , respectively.
a) Find the position vector of their centre of mass.

Thanks,
WeiJing
• October 30th 2012, 05:34 PM
skeeter
Re: Past Year Exam Question
$\bar{x} = \frac{\sum m_i x_i}{\sum m_i}$