Question

1. what happens to the total energy as the skater moves down and up the u - shaped ramp (does the energy disappear or does it change?)

Explanation:

According to the law of conservation of energy, in the absence of non - conservative forces like friction (assuming an ideal situation), the total mechanical energy (sum of kinetic and potential energy) of the skater remains constant. As the skater moves down the ramp, potential energy is converted to kinetic energy. As the skater moves up the ramp, kinetic energy is converted back to potential energy.

Answer:

The total energy remains constant (assuming no non - conservative forces like friction). It just changes form between kinetic and potential energy.