Chapter 6, Problem 3AC

Several African tribes engage in a ritual much like bungee jumping, in which a tree vine is used instead of a bungee cord (a) A 70.8-kg person falls from a cliff with such a vine attached to his ankles. Find the force applied to his ankles if it takes 0.355 s to change his velocity from –18.5 m/s to rest (the negative sign represents the downward direction). (b) Find the force applied to the person’s ankles when he takes 1.98 s to change his velocity from –18.5 m/s to –9. 75 m/s using a manufactured bungee cord (remember that a bungee cord causes the jumper to bounce back upward). (c) Using physics terms, describe why it is safer to use a bungee cord than a tree vine.