Question

A daredevil plans to bungee jump from a balloon 52.0 m above the ground. He will use a uniform elastic cord, tied to a harness around his body, to stop his fall at a point 15.0 m above the ground. Model his body as a particle and the cord as having negligible mass and obeying Hooke's law. In a preliminary test he finds that when hanging at rest from a 5.00-m length of the cord, his body weight stretches it by 1.80 m. He will drop from rest at the point where the top end of a longer section of the cord is attached to the stationary balloon.

(a) What length of cord should he use?
(b) What maximum acceleration will he experience?