ANSWER:
On a roller coaster, kinetic energy is converted to potential energy and vice versa.
Explanation:
Two energies are involved in a roller coaster, kinetic energy and potential energy.
There is a constant transformation from potential energy to kinetic energy and from kinetic energy to potential energy, as there are many ups and many downs on a roller coaster.
In an ascent it is transforming from kinetic to potential and in descent from potential to kinetic.