When riding a roller coaster, you go up and down many hills. As you get to the top of a roller coaster, what energy change is taking place? A. potential energy is changed into kinetic energy
B. kinetic energy is changed into potential energy
C. chemical energy is changed into heat energy
D. heat energy is changed into chemical energy​

A.

Explanation:

The potential energy of the roller coaster increases as the coaster goes up a hill and can be converted to kinetic energy.

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.