So I had an exam today and one of the questions is bugging me. Our professor is out of town for a few days, so we had a proctor and I still can't figure it out using my notes. It was a question about two carts and deals with momentum. Cart A is at rest between two photogates, while cart B is off to the right and it's pushed. An elastic collision occurs. Mass of cart A is 100 g and the first photogate time is 0.2 seconds and second time is 0.5 seconds going back through. Find mass of cart B and the initial and final energy of the system.

I didn't think there was enough info supplied, so I was really lost. Maybe I missed something in the question, but this is what I believe it was. Help Please.

see other post.