One who writes down the births deaths and vital statistics of a population

The answer is Demographer.

Demography is the study of the characteristics of human populations, such as size, growth, density, distribution, and vital statistics, therefore a demographer is a person who studies changes in numbers of births, marriages, deaths, etc. in an area over a period of time.

the answer is a quran

~kinetic ~potential

explanation:

kinetic and potential energies would be types of mechanical energies.