impulses

In physics, impulse is the change in momentum produced by a force acting over a time interval. It is the integral of force with respect to time, J = ∫ F dt. The impulse-momentum theorem states Δp = J, meaning momentum changes by the amount of impulse. Impulse depends on both force magnitude and duration; a sharp, brief push can equal a longer, weaker one. Units are newton-seconds (N·s). Impulses are central to explanations of collisions, recoils, and propulsion.

In signal processing, an impulse (Dirac delta) is an idealized, instantaneous input used to probe systems. The impulse response is the output when the input is an impulse and fully characterizes a linear time-invariant system. Convolution with the impulse response yields the system’s response to arbitrary inputs. Real systems approximate impulses with short, broadband pulses.

In neuroscience, a nerve impulse or action potential is a rapid, transient rise and fall in membrane potential that propagates along neurons. It is triggered when threshold is crossed, and follows an all-or-nothing pattern. Conduction speed depends on axon diameter and myelination; myelinated fibers exhibit saltatory conduction, increasing speed.

In psychology, impulsivity refers to acting with limited forethought or consideration of consequences. It is a trait measured in behavioral assessments and linked to risk-taking and certain disorders. While sometimes advantageous in fast-evolving situations, excessive impulsivity can lead to negative outcomes.