1. The problem statement, all variables and given/known data A 29.0 g ball is fired horizontally with initial speed v0 toward a 100 g ball that is hanging motionless from a 1.10 m-long string. The balls undergo a head-on, perfectly elastic collision, after which the 100 g ball swings out to a maximum angle θmax = 50.0° see image for question 2. Relevant equations Ki + Ui = Kf + Uf vp = √[2*g*L*(1 - cosθ)] mb*v0 = mp*vp + mb*vb 3. The attempt at a solution I suspect you have to use the mass ratio and it's relation to the ratio of momentum or kinetic energy, but I have been unsuccessful in getting the correct answer. The tried answers are availible along with the question in the image.