I only know about the Water tank which is the most accurate. You place your body in it, and weights are added I think. Somehow some measurements are gathered to get your body fat weight. Online calculators exist, as well as electronic waves that are sent int your body, the echo is recorded and analyzed.
Im not so sure but it should be the
instantaneous speed
Answer: it reduces dependence on fossil fuels. Disadvantage: it would emit pollution into the air.
Answer:
I think the answer is D,54 joules