Impulse (J = FΔt)

Also known as change in momentum · impulse-momentum theorem

J=FΔtJ = F \, \Delta t

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Impulse is force applied over time, and it equals the change in momentum it produces — J carries the same units as momentum (N·s = kg·m/s). That trade-off is the whole idea behind airbags and crumple zones: the momentum change in a crash is fixed by the speeds involved, so stretching the contact time Δt slashes the average force F your body must absorb.

Impulse (J = FΔt)
J=FΔtJ = F \, \Delta t
Where
  • JJ= Impulse (change in momentum)
  • FF= Average force
  • Δt\Delta t= Contact time
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