Hi, 1. The problem statement, all variables and given/known data There is a 2.0 kg mass riding on top of a 3.8 kg mass as it oscillates on a frictionless surface with a period of 3.0 s. The upper block just begins to slip when the amplitude is increased to 50 cm. What is the coefficient of static friction between the blocks? The spring constant is 70 N/m. 2. Relevant equations 3. The attempt at a solution I am having a hard time incorporating friction into my equations. I believe that I am supposed to use F=uN, w = (k/m)^.5 as well as w = 2(pi)f and V = wA. Any ideas on how to start this one? Thanks!