Isometric and Isotonic Contraction
When walking, you push against the floor with your feet to propel yourself forward. This pushing action creates a reaction force from the floor that helps you move in the desired direction.
Because your feet are not accelerating, the force exerted by the floor upon your feet must be exactly the same as the force exerted by your feet on the floor. If you are standing, the amount of force exerted by your feet, and thus the amount of force exerted by the floor, is equivalent to your weight.
If your feet are off of the floor, then the chair exerts your total weight against you.
Yes, according to Newton's third law of motion, the floor exerts an equal and opposite force against your feet when you stand on it. This upward force is what supports your weight and prevents you from falling.
When going uphill, you are primarily pushing against gravity to move your body and any additional weight uphill. Additionally, you are also exerting force against any friction present between your feet and the surface you are walking or climbing on.
Force A is Gary's weight pulling him downward towards the ground. Force B is the reaction force from the ground pushing back up against Gary's feet as he rests on the ground.
There may not be enough friction between your feet and the floor. You need friction to be able to exert a force against the floor, to balance yourself and move in the direction you desire.
This involves Newton's third law of motion; for every force there is an equal and opposite force. If your weight is 140 lbs, then you're exerting 140lbs of force on the floor. In response, the floor is exerting 140lbs of force on you.
Example: Measure a floor-- it is 20 feet long and 30 feet wide 20 x 30 = 600 square feet.
One example of static electricity is when you drag your feet across the floor and then shock someone. The shock is the static electricity.
The floor's area is: 1,296 square feet.
The pressure on an object increases with depth because there is more pushing on it. For example, four feet below the surface of water, there is a layer of water four feet thick pushing on the object and the water around it. Now several miles down, this layer of water is much thicker, and so exerts more pressure when it is pushing down. In this example I used water, but the same can be applied to any fluid, including air.