How does a human arm work?

Simple answer, Evolution, without them early human species would have never survived. Improved answer: simply because life on this planet was once just a clump of cells, then some became bigger and...

You can use free weights and do sets of 12,10,8 a few times a day and eat protein and you will get somewhere or if you have the money go to the gym they have a lot of work out machines that will get...

well c-;

Force equals mass times acceleration, so you need to know those two variables before that question can be answered.