A 300 lb bungee jumper wants to jump from the top of a 230 ft high bridge and be able to just touch the water below (Part A figure) . Given that the bungee cord has a spring constant of 11.1 lb/ft, what should the bungee cord's relaxed length, l, be for this jump?

Answer 1

cord potential energy at maximum allowed extension = potential energh loss of jumper, at the bottom

(1/2)k(230-L)^2 = M*g*230

Solve for L.
k is the spring constant.

Mass must be in slugs, or use M*g = 300 lb.