Impuls

Impuls, in many languages including German, denotes the same core idea as the English word impulse: a sudden force, encouragement, or moment of momentum that initiates change. In scientific and technical usage, it often refers to a quantity that measures the effect of a force acting over a short period of time. The term also appears in everyday language to describe a spur-of-the-moment decision or action.

In physics, impulse is defined as the integral of force with respect to time: J = ∫ F dt. It is a vector quantity and equals the change in momentum of a body, Δp, according to the impulse–momentum theorem. When force F is constant over a time interval Δt, impulse simplifies to J = F Δt. The units of impulse are newton-seconds (N·s), or equivalently kilogram meter per second (kg·m/s). The direction of the impulse matches the direction of the applied force.

In signal processing and systems theory, an impulse refers to an idealized, instantaneous input such as the Dirac delta function δ(t). The impulse response h(t) of a linear time-invariant system describes how the system reacts to that impulse. Any input signal x(t) can be expressed as a sum of shifted impulses, and the system’s output y(t) is the convolution y(t) = x(t) * h(t). The area under δ(t) is 1, a property used to characterize system behavior.

Other uses include impulse noise in electronics, and the concept of impulsive actions in decision-making. The term remains a common shorthand for sudden, brief forces or motivations across disciplines. See also impulse response, impulse noise, and impulse buy for related concepts.