1. The problem statement, all variables and given/known data A 70 kg bungee jumper jumps from a bridge. She is tied to a bungee cord whose unstretched length is 13 m , and falls a total of 37 m . Calculate the spring stiffness constant of the bungee cord, assuming Hooke's law applies. 2. Relevant equations 0.5kx^2 (final) + mgy (final) + 0.5mv^2 (final) = mgy (initial) + 0.5kx^2 (initial) + 0.5mv^2 (initial) 3. The attempt at a solution Her mass won't change throughout the problem but for the sake of keeping everything organized, I'll just share what I plugged in. K is the unknown, but aren't the initial "x" and "y" positions 13 m? That's a little weird to me and that's why I'm thinking I used in the correct equation. I found out I didn't need the 0.5mv^2 at all because kinetic energy is zero at the beginning and end.