Describe a theme-park ride that has constant speed but changing velocity?

Why is the energy that results from a roller coaster's position at the top of a hill referred to as potential energy?

The electric field between square plates of a parallel-plate capacitor has magnitude e. the potential across the plates is maintained with constant voltage by a battery as they are pulled apart to twice their original separation, which is small compared to the dimensions of the plates. the magnitude of the electric field between the plates is now equal to a)e b)e/4 c)e/2 d)4e e)2e

Explain what happens at the saturation point when adding salt to water at room temperature.