impulsu

Impulse is a physics concept that describes the change in an object's momentum resulting from a force acting over a time interval. It is defined mathematically as J = ∫ F dt, and for a constant force F acting for a duration Δt, it simplifies to J = F Δt. By the impulse-momentum relation, the impulse delivered to an object equals the change in its momentum: J = Δp = p_f − p_i. This means that if a force acts longer or with greater magnitude, the resulting momentum change is larger.

Impulse is a vector quantity; its direction is the same as the average direction of the applied force. In SI units, impulse is measured in newton-seconds (N·s), which is equivalent to kilogram meters per second (kg·m/s). The effect of impulse is to alter the velocity of the object according to Δp = m Δv, where m is mass and Δv is the change in velocity.

For variable forces, impulse is the area under the force–time curve. It can be calculated as the definite integral of F(t) over the time interval of contact. This allows analysis of complex loading scenarios, where the force varies during, for example, a collision or a thrust event.

Applications of impulse theory appear in collisions, braking systems, sports dynamics (such as hitting or throwing), and propulsion. Impulsive forces are typically short in duration but can be very large in magnitude, producing rapid changes in motion. The term impulse has Latin roots (impulsus), reflecting the notion of a push or drive.