Worked example 6.6: 2-dimensional collision Question. Two objects slide over a frictionless horizontal surface. The first object, mass mi 5 kg, is propelled with speed u 4.5 m/s toward the second object, mass m2 2.5kg, which is initially at rest. After the collision, both objects have velocities which are directed θ 30° on either side of the original line of motion of the first object. What are the final speeds of the two objects? Is the collision elastic or inelastic?