Question

A girl weighs 200 newtons. How
much work does she do
climbing 10 meters of steps?

Answer 1

w=fscosx
w=fscos0 {as x(angle between force and displacement)=0 because force and displacement is in same direction}
w=200*10
w=2000 joules

Answer 2

When she gets to the top, she has (200x10)=2000 more joules of potential energy than she had at the bottom. But unfortunately, she has to do a lot more work than that in order to get there. She has to lift a leg, put it down, and then extend it, for each step, for example. The human body is not 100% efficient.