One day, a father weighing 80 kg and a mother weighing 65 kg go to the mountains. Together they arrive at a hut, which is at an altitude of 640 m. The father decides to rest, so he puts down his backpack and lies down on a lounger. The mother walks to a vantage point, which lies 45 m above the hut and is 100 m away from the hut.
Calculate the potential energy of the father on the lounger.
Calculate the potential energy of the mother at the vantage point.
What is the mass of the mother's backpack for the mother with her backpack at the vantage point and the father on the lounger to have the same potential energy when viewed from sea level?