1. The problem statement, all variables and given/known data a 6 kg, originally held at rest in position 1 as shown in the diagram below, slides down a frictionless quadrant of a verticle circle of radius 15 m. It then collides elastically with another 16 kg mass at rest at position 2. They bounce off each other and move on the horizontal frictionless surface and up the frictionless quadrant of a verticle circle on each side. Calculate the verticle height "H" for each ball at which they would momentarily come to rest after elastic collision. Diagram: http://s1176.beta.photobucket.com/user/LolaGoesLala/media/jkmlkm.jpg.html 3. The attempt at a solution So i was thinking of starting with the kinetic energy formula btu then i realised i need to include the gravitational potential energy but i need the height for it... so can anyone help me out on starting with this problem?