Consider a system to be one train car moving toward another train car at rest. When the train cars collide, the two cars stick together. What is the total momentum of the system after the collision? 800 kg • m/s 1,600 kg • m/s 2,400 kg • m/s 4,000 kg • m/s

Which of the following matches the organisms described with the correct domain? a. archaea--multicellular, eukaryotic organisms that do not have cell walls b. eukarya--single-celled and multicellular organisms, with a defined nucleus and a variety of nutritional sources c. bacteria--unicellular, eukaryotic organisms with cell walls that do not contain peptidoglycan d. bacteria--unicellular, eukaryotic organisms that always lack cell walls