Impulse Calculator
Calculate impulse using J = F·Δt or the impulse–momentum theorem J = m·Δv — with average force and velocity change, in SI units (N·s).
Frequently Asked Questions
What is impulse in physics?
Impulse (J) is the effect of a force acting over time: J = F × Δt. By the impulse–momentum theorem it equals the change in momentum: J = Δp = m × Δv. Its unit is the newton-second (N·s), identical to kg·m/s. A small force over a long time can produce the same impulse as a large force over a short time.
How do you calculate impulse from force and time?
Multiply the average force by the contact time: J = F × Δt. A 250 N force applied for 0.02 s delivers J = 5 N·s. For a varying force, impulse is the area under the force–time curve; using the average force gives the same result.
How do you calculate impulse from mass and velocity?
J = m × (v₂ − v₁). A 0.45 kg football accelerated from rest to 25 m/s receives J = 0.45 × 25 = 11.25 N·s. If you also know the contact time, the average force is F = J ÷ Δt — for a 0.01 s kick, that is 1,125 N.
Why do airbags and crumple zones reduce injury?
In a crash, the momentum change (impulse) is fixed by the speed and mass — what safety systems change is the time over which it happens. Since F = J ÷ Δt, stretching the stopping time from ~0.01 s to ~0.1 s cuts the peak force on occupants by roughly ten times. The same physics applies to bending your knees when landing a jump.