Particle A of mass  m1 moving with velocity 3i^+j^ ms−1  collides with another  particle B of mass  m2 which is at rest initially.  Let V1→ and V2→  be the velocities of particles A and B after collision respectively.  If  m1=2m2 and after collision V1→=i^+3j^ms−1 , the angle between  V1→  and V2→  is