Lukkehastighet

Lukkehastighet, or "terminal velocity," refers to the constant speed that an object reaches when the force of gravity pulling it downward is balanced by the upward force of air resistance, or drag. This concept is fundamental in physics and applies to various scenarios, including the motion of objects falling through a fluid, such as air or water.

When an object falls through the atmosphere, it initially accelerates due to gravity. As its speed increases, air resistance also grows, opposing the motion. Eventually, the drag force equals the gravitational force, and the object stops accelerating. At this point, it has reached its terminal velocity. The speed at which this occurs depends on several factors, including the object's mass, shape, and cross-sectional area, as well as the density of the surrounding medium.

In free-fall conditions, such as skydiving, terminal velocity for a human in a belly-to-earth position is approximately 120–170 kilometers per hour (75–105 miles per hour). This speed varies slightly based on body position and weight. For heavier or more compact objects, such as a falling brick, terminal velocity is typically lower due to greater drag forces relative to their mass.

Terminal velocity is also relevant in meteorology, where it describes the speed at which precipitation, like rain or snow, falls through the atmosphere. Additionally, it plays a role in engineering and aviation, where understanding drag and stability is crucial for designing safe and efficient systems.

The calculation of terminal velocity involves complex fluid dynamics, often requiring empirical data or computational models. For simple cases, it can be approximated using Stokes' law for small, spherical objects or other drag equations for larger or irregularly shaped objects. Terminal velocity ensures that objects in free fall eventually reach a stable speed, preventing infinite acceleration.