Let a1, a2,…. an be the accelerations of a system of point masses m1, m2 … mn.
Acceleration of the centre of mass of the system is given by,

= \(\frac{resultant\,force}{total\,mass}\)
= weighted average of forces
x, y and z components of can be obtained similarly.
For continuous distribution, \(\overrightarrow{a}_{cm}\) = \(\frac{\int\,\overrightarrow{a}dm}{M}\)