Impulse (Physics)
Definition
The total 'shove' delivered by a force over time — a big force for a short time can equal a small force acting much longer.
Unit: newton-second (N·s)
Technical definition
J = F·Δt = Δp. Impulse is the time integral of force and equals the change in momentum; like momentum, it is a vector.
Example
A 0.15 kg tennis ball struck with 300 N for 0.005 s receives 1.5 N·s of impulse and leaves the racket at 10 m/s.
Common confusion
Impulse is not the same as impact force. Airbags work by stretching out Δt so the same impulse — stopping you — needs a far smaller peak force.