1. The problem statement, all variables and given/known data A railway waggon of mass m=20t is travelling with v=18km/h. It then hits 10 other stationary railway waggons, with each one having the same mass of m=20t . (Friction is not being considered) 2. Relevant equations a) Assume the 10 railway waggons are connected through strong metal springs: Is it an elastic or inelastic collision. Describe what happens precisely and determine the velocity of the waggons after the impact. b) The 10 waggons are connected through metal rods. Is it an elastic or inelastic collision? What are the collision "partners"? Determine the velocity of the waggons after the impact. c) All 10 waggons have a automated connector socket, which upon impact connects each waggon with the next. Is it an elastic or inelastic collision. Determine the velocity of the waggons after the impact. How big is the loss of kinetic Energy? 3. The attempt at a solution So let's start with what I have thought out for b) All waggons being connected with a metal rod, we could also assume the other waggons act like one big waggon with 10x the mass of one waggon (m=100t). It's definetly an elastic collision, so we can just work with the momentum formula (see attached files): so v1' (of the lonely waggon) would be -8.18m/s (going in the opposite direction) and for the other waggons v2' = 0.909m/s Is this correct? But what about a) and c) I could think that for c) we have an elastic collision upon first impact and then it goes on to be a inelastic collision. Is that correct?