What happens to gravitational potential energy as a rollercoaster moves down a hill?

At the top, the roller coaster has a very large amount of potential energy. This amount of potential energy is present because the roller coaster is at a elevated place with respect to the ground. While the roller coaster goes down some of the potential energy is lost depending on the change in height and is converted to other energy. As the roller coaster is losing the potential energy, it gains some kinetic energy since this type of energy is dependent on the speed of the object moving and the mass. Therefore the answer i believe is where potential energy is converted to kinetic energy.

Multiply the 3 dimensions, assuming it is a rectangular cuboid, to get the volume in cm³ divide mass by volume to get density in g/cm³