Does Air Feel Heavier When Falling from High Altitude?

Most people might have wondered at some point whether the air they breathe feels denser or heavier when they jump from a high altitude.

When a free-falling jumper descends from a great height, the air momentarily feels less dense, creating a sensation of lightness. This is due to the dynamic pressure experienced during the free-fall. Dynamic pressure is a function of air density and the square of the speed. As speed increases, dynamic pressure grows, which in turn leads to a sensation of a lighter air.

The Role of Terminal Velocity

However, the perception of air density quickly changes as the jumper reaches terminal velocity, a state in which the force of dynamic pressure equals the jumper's weight. At this point, the sensation of lightness disappears, and the air feels remarkably similar to how it would feel at ground level.

At terminal velocity, the dynamic pressure experienced by the jumper remains constant, and it is here that the air's density and the jumper's speed are in a perfect balance. Even as the air density increases with altitude, the jumper's speed decreases to cancel out the effects, keeping dynamic pressure unchanged and the feeling the same.

Understanding Terminal Velocity

Terminal velocity is a crucial concept in understanding this phenomenon. It is the maximum speed a free-falling object can reach when the air resistance equals the force of gravity pulling the object downward. Once reached, the object's acceleration stops, and it continues to fall at a constant speed.

The concept of terminal velocity is not limited to skydiving. It applies to any object moving through a fluid, whether it's air or water. The exact terminal velocity depends on various factors, including the object's mass, surface area, and shape.

Dynamic Pressure and Its Impact

Dynamic pressure, denoted by the letter #9632;, is a measure of the kinetic energy per unit volume in a fluid. It is directly proportional to the square of the velocity and the density of the fluid. Mathematically, dynamic pressure can be expressed as:

Dynamic Pressure 0.5 * ρ * v^2

Here, ρ represents the density of the fluid, and v is the velocity of the object relative to the fluid.

The impact of dynamic pressure on the human body during a free-fall can be significant. As the jumper reaches terminal velocity, the body is subjected to a steady amount of force, neither increasing nor decreasing. This is why, once terminal velocity is reached, the sensation of air density remains constant, despite changes in altitude.

Conclusion

In summary, while the air may feel momentarily lighter at the beginning of a free-fall, this sensation is due to dynamic pressure. As the jumper reaches terminal velocity, the air feels the same as it would at ground level. This is because the force of dynamic pressure equals the jumper's weight, neutralizing the effects of air density changes.

Understanding these concepts not only helps in appreciating the physics of falling but also provides valuable insights for skydivers and engineers designing free-fall equipment.

Further Reading:

The Physics of Skydiving Understanding Terminal Velocity Dynamic Pressure in Fluid Dynamics