An atomic nucleus of mass m traveling with speed v collides elastically with a target particle of mass 2m (initially at rest) and is scattered at 90....

An atomic nucleus of mass m traveling with speed v collides elastically with a target particle of mass 2m (initially at rest) and is scattered at 90. 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 kinetic energy is transferred to the target particle?