Two equal masses travel towards each other on a frictionless air track at speed pf 60cms-1 and 30cms-1.they stick together on impact what is the speed of the masses after impact?

Use conservation of momentum on this problem:


m_1v_1 + m_2v_2 = (m_1 + m_2) v_f


Remember that since the mases are initially moving toward each other, one positive initial velocity and the other is negative.