is all of the gravitational potential energy of the skater turned into mechanical kenetic energy? If yes why? If not where does it go?
No, all of the gravitational potential energy of the skater is not converted into mechanical kinetic energy. According to the law of conservation of energy, energy cannot be created or destroyed, only transformed from one form to another.
When a skater slides down a ramp, gravitational potential energy is initially converted into both mechanical kinetic energy and some other forms of energy. These other forms of energy can include sound energy due to friction between the skates and the ramp, heat energy generated by friction, and air resistance.
Additionally, some amount of gravitational potential energy is also used to overcome air resistance and friction throughout the skater's motion. As a result, the skater will not have all the initial gravitational potential energy as mechanical kinetic energy at the bottom of the ramp.