A man will exert the greatest pressure when he?

Analysis

The question asks us to identify the condition under which a man exerts the greatest pressure. To solve this, we must look at the physical relationship between force, area, and pressure.

Concept: Pressure

In physics, Pressure ($P$) is defined as the force ($F$) applied perpendicularly per unit area ($A$). The formula is:

From this formula, we can observe two things:

1. Force ($F$): In this scenario, the force is the man's weight, which remains constant regardless of his position.
2. Area ($A$): Pressure is inversely proportional to the area. This means that as the area of contact decreases, the pressure increases. To exert the greatest pressure, the man must minimize the area of contact with the ground.

Step-by-Step Solution

1. Analyze the options based on contact area: • Lying flat (on back or belly): The contact area is very large (the entire surface area of the body). This results in the lowest pressure. • Standing on both feet: The contact area is the surface area of two feet. This results in moderate pressure. • Standing on the toes of one foot: The contact area is extremely small (just the tips of the toes on one foot).

2. Apply the principle: Since the man's weight (Force) is constant, the smallest area of contact will produce the highest pressure. Standing on the toes of one foot provides the smallest possible surface area among the given choices.

Conclusion

Because the area of contact is minimized when standing on the toes of one foot, the pressure exerted is at its maximum.

The correct option is D.

Exam Tip

Whenever you see a question about pressure, remember the "High Heels vs. Flat Shoes" analogy. A person wearing high heels exerts more pressure on the floor than someone wearing flat shoes because the weight is concentrated on a much smaller surface area (the heel tip). Always look for the option that reduces the surface area to the smallest possible size!