Final answer:
A person standing on the floor experiences a downwards pull from gravity and an upwards support force from the floor, illustrating Newton's third law of motion. These forces are equal and opposite, ensuring the person does not fall through the floor due to the counteracting normal force.
Step-by-step explanation:
When a person stands on the floor, they experience a pull downward due to gravity, and simultaneously, the floor provides an upward support force. This is an illustration of Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. Hence, gravity pulling down and the support force pushing up are equal in magnitude but opposite in direction, resulting in the person remaining stationary on the floor.
If a person performs an action such as standing on tiptoes or holding a weight, the pressure exerted on the floor can vary due to changes in force and surface area. In both cases, the normal force adjusts accordingly to maintain equilibrium. Moreover, despite the Earth being pulled upwards by the person's weight as well, the Earth's massive size ensures that any movement is imperceptible.
The concept of the normal force is crucial for understanding why, under normal conditions, objects do not fall through the surface they are on despite the gravitational pull. The normal force acts perpendicular to the surface, counteracting the weight of the object and allowing it to remain at rest or to move along the surface without sinking through.