At t = 0, the positions and velocities of two particles are as shown in the figure. They are kept on a smooth surface and being mutually attracted by gravitational force. Find the position of centre of mass at t = 2s.

As no extemal force are acting on the system. The velocity of centre of mass will be constant.initial position of CM is Xcm=1×0+1×101+1=5 mvcm = 1×5-1×31+1 = 1 m/sDisplacement of centre of mass ∆xcm= 1×2 = 2 mHence position of centre of mass ∆xcm = 5+2 = 7 m