1. The problem statement, all variables and given/known data The two blocks in the figure oscillate on a frictionless surface with a period of 1.5 s. The upper block just begins to slip when the amplitude is increased to 36 cm. What is the coefficient of static friction between the two blocks? 2. Relevant equations 3. The attempt at a solution I've tried to think of the forces involved (ie. friction -normal force * coefficient of friction etc) But I'm having trouble incorporating the period and the amplitude into equations with forces in them. Any help is greatly appreciated!