playing bumgy jump

[7bear]

Suppose a boy is playing bumgy jump. When he jumps out and reachs the lowest bottom (instanteous at rest), there is zero K.E.
At that time, there is max. elelastic potential energy in the string. Which energy is changed to it(max. elelastic potential energy) :confused: ?

[Doc Al]

When the boy jumps he has zero KE but maximum gravitational PE (with respect to the ground). It's that gravitational PE which gets transformed into elastic PE.

[Gonzolo]

Of course, the gravitationnal PE first turns into KE, which then turns into the elastic PE.