A car of mass m moving East at speed v (v << c no need to use relativity) collides with another car of mass 2 m moving North with speed 3v. a) What are the x and y components of the center of mass velocity of the system just before the collision? b) If the cars stick together during the collision what is their common speed after the collision? c) Determine the ratio of the total kinetic energy after the collision to the total kinetic energy before the collision? d) Explain why kinetic energy is not conserved but momentum is conserved during the collision I got the first two parts but I'm not sure how to find the ratio of kinetic energy! Please help!