Your instructor tells you that when he is not teaching or doing physics
research, he sometimes performs as a professional juggler. For certain
occassions, he juggles while walking on stilts that make him nearly 9 feet
tall. He explains that the most difficult part of stiltwalking is getting
over the fear of falling, because if he were to fall, his head would accelerate
faster than gravity! He asks you to show this and verify the expression:
"the taller they are, the harder they fall!" Decide if a helmet is
recommended by examining the speed of his head in a fall and comparing
this speed to that of a typical adult falling down or the speed while riding
a bicycle.