Impulse
The vector quantity defined as the integral of a force over the time interval during which it acts, equal to the net change in momentum.
Governing formula
J = ∫ F dt = Δp = m vf - m vi
SI unit
N·s (or kg·m/s)
In depth
According to the impulse-momentum theorem, applying a force over a longer time duration reduces the peak force required to achieve a given momentum change. This principle is fundamental to impact safety engineering.
Examples in the real world
Crumple zones and airbags in automobiles extending collision duration to reduce impact forces on passengers, or a golfer following through on a swing to maximize contact time.