988 A particle of mass m = 1.0 kg, traveling at speed vo= 10 m/s, strikes a particle at rest of mass M = 4.0 kg, and rebounds in the direction from which it came, with a speed v. If the amount of heat produced in this collision is 20 J, find vr. (Define all the quantities you introduce in a sketch, and state clearly from what physical laws your initial equations are derived.)