PROBLEMS TO BE WRITTEN UP AND TURNED IN AT RECITATION

     This problem is due at your first recitation meeting after Mon 11/15.
     It should be written on a single sheet of paper (front and back), or
     if multiple sheets are used, staple them together.  For full credit, 
     the work must be neat, with a clearly labeled free-body diagram.  The 
     labels must be in BOTH words and symbols.  You must BRIEFLY explain 
     your strategy in words, as well as neatly showing your physics 
     equations and math, with proper units. (10 points total)
     
     FISHBANE - CHAPTER 9
     65. A yo-yo is made from two uniform disks, each with mass M/2
         and radius R, connected by a light axle of radius r (so the
         total mass of the yo-yo is M).  A light, thin string is wound
         several times around the axle.  The yo-yo is placed on a
         rough horizontal surface; the coefficient of static friction
         between the yo-yo and the surface is mu_s.  The string is held 
         so that it exits the yo-yo horizontally on the lower side of 
         the stem.  The string is then pulled horizontally with a 
         force of magnitude F.  (a) Assuming the yo-yo rolls without
         slipping, in which direction will the yo-yo roll (towards the 
         puller or away from the puller)?  (b) What is the maximum value 
         of F for which the yo-yo will roll without slipping?