While it might seem like a scenario confined to fiction, the powerful forces of moving air can indeed exert significant influence on the human body. Understanding the science behind this phenomenon reveals that it is not simply a matter of wind pushing horizontally, but a complex interplay of physical principles and individual characteristics that determine how much wind is truly needed to move, or even lift, a person.
Understanding Wind’s Lifting Power
Wind, essentially air in motion, exerts force on objects it encounters. This interaction involves several fundamental physics principles, including pressure differences, drag, and lift. Air moves from areas of higher atmospheric pressure to areas of lower pressure; the greater this difference, the faster the air flows.
Bernoulli’s principle states that as the speed of a fluid, like air, increases, its pressure decreases. When wind flows over and around an object, such as a person, it creates varying air speeds and pressure differences on different surfaces. This pressure differential can generate a force.
Wind also creates drag force, which is the resistance an object experiences moving through a fluid. Drag always acts opposite to the object’s motion relative to the fluid. A larger surface area presented to the wind increases this drag, primarily pushing an object horizontally.
Lift, in an aerodynamic context, is the force component perpendicular to airflow. While commonly associated with aircraft wings, lift can also be generated on other objects. For a person, wind flowing to create an upward pressure differential contributes to potential vertical movement.
Key Variables in Wind’s Effect on Humans
The wind force a person experiences, and their susceptibility to being moved or lifted, depends significantly on individual factors. A person’s weight is a primary determinant; heavier individuals require greater force to overcome inertia. Lighter individuals, such as children, are more easily affected by lower wind speeds.
Another variable is the person’s surface area exposed to the wind. A larger area directly facing the wind increases the drag force. Standing upright, for example, presents a larger frontal area than crouching. Clothing type and fit also influence this, with loose garments increasing effective surface area.
Posture or shape also alters how wind interacts with the body. Adapting posture minimizes air friction and drag. Leaning into a headwind, for instance, reduces frontal area and decreases wind force. Conversely, a posture creating an “airfoil” effect could generate upward lift.
What Wind Speeds Can Do
The effects of wind on a person range from discomfort to potential lift, depending on speed. At 20-30 mph, wind affects balance, making walking challenging. At 30-40 mph, walking against the wind becomes noticeably inconvenient, requiring significant effort.
At 40-45 mph, a 100-pound person might be moved, though not necessarily knocked down unless they lose balance. Gusts of 50 mph can push and knock a person down. At 60 mph, walking is very challenging and exhausting, with a high risk of being blown over and injured.
To lift a person off their feet, much higher wind speeds are typically required. Wind tunnel tests show an average-sized man could be lifted at 78-80 mph. Sustained winds at or above 70 mph can lift most people, though this often requires specific body positioning.
In extreme conditions, like hurricane-force winds (e.g., Category 4, 130-156 mph), moving on foot is extremely difficult, with significant risk of injury or death from flying debris. While wind alone at these speeds can make a person airborne, the greatest danger often comes from extreme gusts, specific body positioning, and hazardous wind-borne objects.