A bungee cord can stretch, but it is never compressed. When the distance between the two ends of the cord is less than its un- stretched length L0, the cord folds and its tension is zero.

A bungee cord can stretch, but it is never compressed. When the distance
between the two ends of the cord is less than its un- stretched length L0, the cord folds and its tension is zero. A particular bungee cord has an unstretched length of L0 = 19 m; when it is stretched to L &gt; L0, the cord’s tension obeys Hooke’s law with “spring” constant 79 N/m.
To test the cord’s reliability, one end is tied to a high bridge of height 55 m (above the surface of a river) and the other end is tied to a steel ball of mass 89 kg, which is dropped off the bridge. The ball stops in the air a few meters before it hits the water — then the cord pulls it back up.
Find the ball’s height above the water’s surface at this lowest point of its trajectory. The acceleration of gravity is 9.8 m/s2 . For simplicity, neglect the cord’s own weight and inertia as well as any air drag on the ball and the cord.