A 390-N child is in a swing that is attached to a pair of ropes 1.9 m long. Find the gravitational potential energy (in JOULES) of the child–Earth system relative to the child's lowest position at the following times.
A) when the ropes are horizontal
B) when the ropes make a 28.0° angle with the vertical
C) when the child is at the bottom of the circular arc
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