1. The problem statement, all variables and given/known data A mass of 120 g rolls down a frictionless hill, reaching a speed of 4.2 m/s. This mass collides with another mass of 300 g that is at rest and attached to a spring with constant 30 N/m. The two masses stick together and enter into periodic motion. What is the equation for the motion? A) x(t)=0.266 sin(8.45t) B) x(t)=0.420 cos(10.0t) C) x(t)=0.0706 sin(8.45t) D) x(t)=0.497 cos(15.8t) 2. Relevant equations x(t) = A cos (wt+ phi) equation for wave motion 3. The attempt at a solution I am able to narrow it down to A or C, by using the equation w = (k/m)^1/2, which gives me 8.45. I am unsure how to find A. I have a feeling you need to implement the velocity, but I have tried that, and have also tried using momentum equation to find velocity after impact.