Question

when a woman stands with two feet on a scale, the scale reads 280 N. When she lifts one foot, the scale reads

Answer 1

Unless she places her lifted foot on something else, she's exerting the same weight on the scale.

Answer 2

even the weight may tend to increase

Answer 3

The same, I would think. I've tried that several times and I always weigh the same amount with one foot up. Although not evenly distributed it's still the same amount of matter and everything.