A 0.5 kg lump of clay is moving at 2 m/s in the +x direction of some arbitrarily chosen coordinate system. It has a head on collision with an identical 0.5 kg lump of clay that is moving at 2 m/s in the opposite -x direction. The two individual lumps of clay stick together to become a single 1.0 kg lump of clay. What is the velocity of the pair after the collision?