Final answer:
If you move the skater halfway up the ramp, their potential energy is at its maximum due to elevation, and kinetic energy is zero because they're not moving. The total energy is initially the sum of potential and kinetic energy, which equals the potential energy when stationary.
Step-by-step explanation:
When you move the skater halfway up the ramp and hold them there before letting go, you will notice that the skater has potential energy (PE) due to its elevated position above the ground. At this point, since the skater is not moving, the kinetic energy (KE) is zero. The total energy of the system is a combination of potential and kinetic energy. In this stationary position, the total energy is equal to the potential energy. Once the skater is released and begins to move, the potential energy will start to convert into kinetic energy as the skater goes down the ramp, speeding up, with the total energy remaining constant if we ignore friction and air resistance.