When you walk upstairs, how are you obeying the law of conservation of energy?

Question

Thanks so much. This is for my science class.

Answer 1

At first, it seems that you are not. After all, you're gaining altitude, and yet you're doing it with "nothing." But the law says that energy must be conserved within a closed system. "You" must consider the food that you eat and the oxygen that you breathe. So "you" are not a closed system. One might consider the world that one lives in (the food, the oxygen) as a closed system. Eventually, the Earth itself is not a closed system, because the Sun delivers enormous amounts of energy for every thing and every person to do amazing things, all in "defiance of the law of conservation of energy."

Next question to your science class: How does existence of life on earth square with the the principle that entropy tends to a maximum? (I am sure that you will wow them with your reply.)

Answer 2

What energy is lost or gained? Where is it lost or gained? Lost=gained to satisfy the law. Consider potential energy and kinetic energy. Up has more potential energy. Moving has more kinetic energy. You generate heat as you move. There is friction. There is air resistance to movement. The stairs support you and push back with equal force or else you fall through due to gravity.
Keep thinking. Put it in your own words.

Answer 3

You are using up chemical energy stored in your body, which makes you tired, and you are increasing your potential energy by going up higher, because high things have more potential energy than low things, and the two exactly balance out.