Just to let you all know I really appreciate your help. Problem A person is doing bungee jumping from a 100m platform. Let's say that the rubber cord's coefficient is k = 6500 g/s^2. Would a 60 kg person hit the ground when jumping using that rubber cord? The two equations that are given to use are Force - -(spring constant)(elongation) and Hanging mass *gravity = spring constant * elongation. I'm not really sure which formula to use. I think the spring constant is k=6500 and I have done this 60*980 = 58800 but have drawn a blank.