Decelerationens

Decelerationens is the definite form of the noun deceleration used in some Scandinavian languages to refer to the phenomenon of slowing down, or to a particular instance of slowing down. In physics, deceleration describes the decrease in speed, and it is connected to acceleration when the motion is taken as a vector quantity.

Conceptually, deceleration is described by the acceleration vector a, defined as the time derivative of velocity v (a = dv/dt). If the velocity changes in such a way that its speed decreases, the component of acceleration along the direction of motion is opposite to v. The magnitude of this deceleration is |a|, and, when talking about speed alone, deceleration can be expressed as -dv/dt for cases where dv/dt is negative.

Measurement and units are standardly expressed in meters per second squared (m/s^2). In practical and engineering contexts, deceleration is also described in terms of g-forces, where 1 g equals 9.81 m/s^2. Modern instrumentation, such as accelerometers, can measure deceleration along multiple axes and are used in vehicles, aircraft, and safety systems to evaluate braking performance and occupant protection.

Causes of deceleration include friction between contacting surfaces, air drag, counteracting propulsion or braking forces, and the component of gravitational force on an incline. In safety engineering, limits on deceleration are specified to reduce injury risk; in vehicle dynamics, deceleration is a key parameter for braking performance and control.

Example: If a car slows from 20 m/s to 0 in 4 seconds, the deceleration is a = (0 − 20)/4 = −5 m/s^2, with a magnitude of about 0.51 g.