okay I think my brain is fried cause I've never before had so many problems in one day anyways... 1) Two billard balls of equal mass move at right angles and meet at the origin of an xy coordinate system. A red one is moving upwards along the y axis at 2m/s, and a green one is moving horizontally (to the right) along the x axis at 3.7m/s. After the collision (elastic), the green ball is moving along the possitive y axis. What is the final direction of the red ball and what are their two speeds? now since I use conservation of momentum I am getting that the green ball would be moving up the y axis (90 degrees) @ 2m/s, and the red ball is moving along the x axis (0 degrees) @ 3.7m/s. I do not have this question in the answer key but I am more then 100% sure that this should be correct, am I missing something or is it really right? now 2nd one I don't really have a solution as it doesn't involve numbers and only algerbra and I hate algebra, so this one is where I really need some help if possible: 2) An atomic nucleus of mass m travelling with speed v collides elastically with a target particle of mass 2m(initially at rest) and is scattered @ 90 degrees. a) At what angle does the target particle move after the collision b) What are the final speeds of the two particles c) What fraction of the initial KE is transfered to the target particle now for this one I am lost as to where to even start, I'm pretty sure I should be using conservation of momentum equationsalmost like in the previous one, except that the mass is different so that cannot be cancelled out, but the letters are messing with my head.