A ride at an amusement park attaches people to a bungee cord, pulls them
straight down to the ground, and then releases them into the air. When they
are pulled to the ground, the bungee cord (which has a stiffness constant of
35 N/m) is stretched 100 m beyond its unloaded length. What restraining
force is required to hold a man with a mass of 90 kg to the ground just before
he is released? (Recall that g = 9.8 m/s2)