1.  

You are helping a friend move. Consider two boxes that have masses in factors of m; one of mass 6m and the other of mass 8m. The coefficient of static friction between the two boxes is very large. The coefficient of static friction between the boxes and the floor is 0.8 and the coefficient of kinetic friction is 0.1. You stack the two boxes on top of each other to slide them on top of the horizontal ground at a certain constant velocity. You push the two boxes on the floor until you break static friction. You continue pushing with this threshold force after they start to slide. You push for a certain time t, let go, then let it slide to a stop. How much time does it take to slide to a stop as a factor of the time you push t?