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The change in Gravitational Potential Energy (GPE) is actually 0! Think about it:
What is the formula for it?
Well, GPE = mgh.
So, when the height is the same in both cases, we know the gravitational potential energy is the same. Therefore, change in GPE = 0.
Sure, GPE did transform to KE during the swing, but all of that KE transformed back into the original amount of GPE.
Hope this helped! Please press “Thanks!”