Why do we include femtometer on this scale if we cannot cannot know for certain the size of objects when they are this small?

the most common energy conversion is from kinetic energy to potential energy, and then from potential energy to kinetic energy.

later on comes the heat energy, mechanical energy, and other energy conversions.

this energy conversion is so common that we can find it in our day to day lives as well.

- one of the most common energy conversions involves the changing of potential energy to kinetic energy or kinetic energy to potential energy

not sure if this is what you'r looking for eubacteria and archaebacteria