Let's revisit our Harley-Davidson in Exercise 26.  If I choose a cliff
that's 1200 meters above sea level (about the height of parts of the Grand
Canyon in Arizona), and push the Harley horizontally off the cliff:

   (a) How fast would the Harley have to be going in order for it to 
       go into a stable orbit around Earth?
   (b) How fast would the Harley have to be going in order for it to
       escape Earth's gravity altogether and fly off into space?
   (c) Let's say I fail to achieve either of these speeds, and thus 
       the Harley-Davidson falls to Earth,
       1200 m below.  How much gravitational force is Earth exerting
       on the Harley when it's one inch off the ground?  (Remember that
       the Harley has a mass of 450 kg.)
   (d) How does the amount of force compare to the amount of
       force in Exercise 26, part (d)?  Does the motorcycle, upon
       hitting the ground, suffer more, less, or equal damage here than
       the situation in Exercise 26, where it falls 80 meters?  
       Please explain how the answers to these two
       two questions can both be correct, even 
       though they may seem contradictory.