A human in freefall typically reaches a terminal velocity of about 200 kilometers per hour (approximately 120 miles per hour) when in a stable, belly-to-earth position. This speed is achieved when the force of air resistance pushing upwards balances the force of gravity pulling downwards.
Understanding Freefall Speed
When a human first begins to fall, gravity causes them to accelerate, meaning their speed continuously increases. However, as speed increases, so does the opposing force of air resistance. Eventually, the upward force of air resistance equals the downward force of gravity, at which point acceleration ceases, and the human falls at a constant speed known as terminal velocity.
Typical Human Freefall Speed
The most commonly cited terminal velocity for a human body in freefall, particularly in a stable, belly-to-earth orientation, is around:
| Aspect | Detail |
|---|---|
| Typical Terminal Velocity | 200 km/h |
| Equivalent Speed (approx.) | 120 mph |
| Common Body Position | Stable, belly-to-earth |
This speed is often measured using precise instruments, such as a GPS device mounted on a skydiver's helmet, ensuring accuracy in determining the rate of descent.
Factors Influencing Fall Speed
While 200 km/h is a common benchmark, the exact speed at which a human falls can vary depending on several critical factors:
- Air Resistance: This is the primary force that slows down a falling object. The greater the surface area presented to the airflow and the faster the object moves, the more air resistance it experiences.
- Body Orientation: A human's body position significantly impacts the amount of air resistance encountered.
- Belly-to-earth: This stable position maximizes the surface area against the air, creating more drag and typically resulting in the aforementioned terminal velocity of 200 km/h.
- Head-down or Diving: By adopting a more aerodynamic, head-down position, a person reduces their surface area facing the air, minimizing drag and allowing them to achieve faster speeds.
- Spread-eagle: Spreading the limbs wide can increase drag even further, slowing down the rate of descent compared to the belly-to-earth position.
Skydivers expertly use these principles of air resistance and body orientation to control their descent speed, allowing them to match speeds with others or adjust their fall for safe parachute deployment.
