Calculate the gravitational potential energy of the child-Earth system

[Chuck 86]

Homework Statement

A 32.2 N child is in a swing that is attached to ropes 1.65 m long. Calculate the gravitational potential energy of the child-Earth system relative to the child's lowest position when the ropes are horizontal

Homework Equations

GPI=mgy
Ke= 1/2 m v^2

The Attempt at a Solution

0+.5mv^2= mgy + 0
i think I am on the right track but i don't seem to get the right answer

 

[Delphi51]

Just use GPI=mgy where y = 1.65 m.