Bungee Jumper Oscillation: Determine Spring Constant

[lindsk]

A bungee jumper, whose mass is 87 kg, jumps from a tall platform. After reaching his lowest point, he continues to oscillate up and down, reaching the low point two more times in 8.5 s. Ignoring air resistance and assuming that the bungee cord is an ideal spring, determine its spring constant.

 

[ideasrule]

What do you think? Can you show us all relevant equations as well as your attempted solution?