Question

Three point masses of 3 kg each have the following position vectors:
r i k r j k r i j mˆ 3 mˆ
; ( ) 3( )1 m ˆ 3 mˆ
( ) 4 mˆ m ˆ
( ) 2( 3 )
2 2 2
1 2 3
t = t + t + t ; t = t + t = t − + t
r r r
Determine the velocity and acceleration of the centre of mass of the system.