1. The problem statement, all variables and given/known data Car 1 (1500kg) is heading north 80km/h, Car 2 (3500kg) is heading east 50km/h. They collide inelastically. a.) Speed and direction of the wreck (car 1 + car 2)? b.) The kinetic energy lost? HERE I HAVE A PROBLEM: c.) What is the kinetic energy of the two-particle systems center of mass before and after the collision? d.) Where was the lost kinetic energy hidden before the collision? 2. The attempt at a solution a. is just vector sum p1+p2 where I can get the velocity by dividing it with the masses (about 12m/s), I can get the angle too (34,438... deg) b. wrecks K minus K of car 1 and car 2 = - 360532,40... J so about 360 kJ lost c. But this one I don't understand. I'd say it stays the same, because... well, that's what I calculated (CM from the v-vectors = v of CM), yet I don't really belive it... d. ... after all shouldn't the K be lost to deformation of bodies (+heat etc.)? Does the K of CM stay the same anyways?