A particle P P\,P of mass m m\,m kg moves at 5 m s-1 along a straight line and collides directly with a particle Q Q\,Q of mass 2 kg moving at 1 m s-1 in the opposite direction. The particles coalesce and move at 2 m s-1 in the original direction of PPP.
Find mmm.
Find the impulse on QQQ, stating its direction.