List three cases in which potential energy becomes kinetic energy and three cases in which kinetic energy becomes potential energy.

A) Potential energy converting into kinetic energy:
1- A ball in free fall from the top of a building: in this example, gravitational potential energy converts into kinetic energy
2- A compressed mass-spring which is released: the spring stretches and the mass is pushed away. In this example, elastic potential energy converts into kinetic energy
3- A positive test charge moving in the direction of the electric field generated by another positive charge: the charge moves from a point at higher potential to a point of lower potential, and electric potential energy converts into kinetic energy

B) Kinetic energy converting into potential energy:
1- A ball thrown vertically from the ground: the ball slows down, and the kinetic energy is converted into gravitational potential energy
2- A block sliding across a table that hits a spring, compressing it: the block slows down and its kinetic energy is converted into elastic potential energy of the spring
3- A positive test charge is fired towards another positive charge that produced an electric field: the charge moves from a point at lower potential to a point of higher potential, so it slows down and its kinetic energy is converted into electrical potential energy

You get 6 for mechanical