From: fortunati.luigi@gmail.com   
      
   The sprinter improves his speed by increasing the pace from 10 to 11   
   steps per second.   
      
   Can he do it without increasing the thrust (force) that his shoes   
   exercise on the ground?   
      
   --   
   - Luigi Fortunati   
      
   [[Mod. note -- This question can be interpreted in a number of   
   different ways.  Anyone replying, please be specific about how you   
   are interpreting it with regard to:   
   * Is the stride length the same between the 10/second and 11/second   
     cases?   
   * Are we considering the *start* of a sprint (when the runner is   
     horizontally accelerating), or the roughly-steady-state phase   
     (when the runner's horizontal speed (averaged over a step) is   
     roughly constant>   
   * Force-of-shoes-on-ground has vertical and horizontal components   
     (and maybe left/right ones too); these are all strongly   
     time-dependent.  So, please be clear about which component(s)   
     you're discussing, and whether you're referring to instantaneous   
     peak values, average values during foot-in-contact-with-ground   
     time, or something else altogether.   
   -- jt]]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)