Problem 3 (10 points) A 400 - N child is in a swing that is attached to a pair of ropes 2.00 m long. Find the gravitational potential energy of the child-Earth system relative to the child's lowest position when (a) the ropes are horizontal, (b) the ropes make a 30.0 angle with the vertical, and (c) the child is at the bottom of the circular arc. Solution