1. The problem statement, all variables and given/known data A curling stone with initial speed vi1 collides head-on with a second, stationary stone of identical mass, m. Calculate the final speeds of the two curling stones. 2. Relevant equations See attached picture 3. The attempt at a solution I solved for vf1 as shown, but my answer was wrong. I got vi1-vf2=vf1, but the correct answer is vf1=0. What did I do wrong?