6. Potential energy converts to Kinetic energy and Kinetic energy will convert to Potential energy. Why does the total energy stay the same? *
The energy is not being created or destroyed: only transformed.
Total energy does not stay the same as some is always lost as heat.
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Energy stays the same because the energy has no where to go but in a system.

The total amount of energy and matter in the Universe remains constant, merely changing from one form to another. ... Once the potential energy locked in carbohydrates is converted into kinetic energy (energy in use or motion), the organism will get no more until energy is input again.

meteorologists would compare a new weather map with one 24 h old to see how fast a front is moving.