1. The problem statement, all variables and given/known data A neutron (m= 1.6 x10-27) moving with speed Vo strikes a stationary particle of unknown mass and rebounds elastically straight back along its path with a velocity of .7Vo. What is the mass of the struck particle? 2. Relevant equations P initial = P final Ke initial = Ke final 3. The attempt at a solution alright i tried saying that the velocity imparted on the stationary particle was .3Vo but that gave me an answer of a mass of a neutron when the actual answer is 9.46 x 10-27. i know: v1i = Vo v2i = 0 v1f = .7Vo but i am unsure as how to continue on from here. Please help.