This is my first post on PF. I've decided that I really want to learn physics, not for school, but because physics can be fun! I'm trying to understand what FN is. I understand it is the force exerted by the ground working upwards contrary to the force of earth's gravitational pull. I understand that FN is your weight when standing. I also know that it decreases while you bend down (during the duration of the bend), and stand or jump up (during the time you're pushing off the ground). However, I'm confused about situations that are a little more complicated. Say you're standing, and drive one of your feet into the ground. It seems to me that all you're doing is shifting your weight from one foot the other. Is that what's really going on? Is it possible to increase your weight by pushing your foot into the ground below you? What about stomping? In the previous case, we didn't lift the foot up off the floor, just pushed it downwards. What if we lift a foot off the ground and stomp? The ground has to exert a corresponding FN to counter the downward drive of the foot. But I'm not sure if a simple shift in weight is going on between one's two feet, or if one needs to add mg and the ma (where a is the upwards acceleration provided by the floor) to get FN. Simply put, is it possible to stomp greater than one's weight? All of the above questions ultimately derive from an uncertainty about how forces act, not on a solid object, but on a person with joints and limbs.