Originally Posted by

**thermalwarrior** I have the following information:

A particle A of mass m is moving along a smooth horizontal surface with velocity of 2i + 3j. A second particle of mass 3m is moving with velocity 6i - 5j, collides with A at the origin at t=0. After this the particles coalesce.

question:

Find the expressions of __R__a(t) and __R__b(t), the respective position vectors of the particles A and B at time <0. Hence find the position vector of the centre of mass of the system before the collision. Hence determine the velocity of the centre of mass.

how do i go about this?

cheers