Last one is mob because that’s a negative connotation
This depends on your age and what language you are trying to learn really. Think about it this way, when you were born, how long did it take you to learn English (or your native tongue)? About five years right? This also depends on a bunch of other different factors like how much you practice, your determination, and the fluency of the language your speaking. So really there is no real definite answer because all people are different, but if I were to say, I'd say about five years...
In science, kinetic energy is usually measured in joules.
Some of the measurements included, calories, thems and kilowatt-hours.
Good luck :)
