Problem: A 1.0 kg mass is riding on top of a 5.0 kg mass as it oscillates on a frictionless surface. The spring constant is 50 N/m and the coefficient of static friction between the two blocks is 0.50. What is the maximum oscillation amplitude for which the upper block does not slip? I don't know where to start. I have looked at trying to do it by looking at the total mechanical energy, but there are too many unknown variables. Any hints to help me get started would be appreciated.