pysäytysvoima

Pysäytysvoima is a Finnish term referring to stopping power or the effectiveness of an object, weapon, or method to halt a moving target or motion. In common usage it appears in discussions about firearms and ballistic performance, but the concept also appears in physics as the force required to stop a moving body. The term is descriptive rather than a single, standardized measurement.

In firearms and terminal ballistics, pysäytysvoima describes how effectively a projectile can incapacitate or stop a target. It is influenced by multiple factors, including the projectile’s mass and velocity, design and construction (for example, expansion or fragmentation), the amount of energy transferred to the target, and how that energy is distributed within the target. Real-world outcomes also depend on shot placement, the target’s anatomy and conditions, clothing, distance, and barriers. Because of these variables, pysäytysvoima is typically discussed as a comparative or qualitative concept rather than a precise metric.

Measurement and interpretation of pysäytysvoima are subjects of debate. Common indicators include kinetic energy at impact, depth and characteristics of penetration, expansion and yaw behavior, and historical statistics on stopping incidents. However, there is no single universally accepted standard to predict incapacitation, since real-world results depend on many interacting factors, making comparisons context-dependent and sometimes problematic.

From a physics standpoint, stopping force can be described by classical mechanics: F = Δp/Δt and F = m a. If a moving object of mass m is brought to rest over a stopping distance d, the average stopping force is F = (1/2 m v^2)/d, and the deceleration is a = v^2/(2d). Understanding pysäytysvoima thus involves both energy transfer and the dynamics of deceleration or interaction with a target.

See also terminal ballistics, kinetic energy, and bullet design.