Impulse Calculator

Impulse explains why a long soft stop hurts less than a short hard one: the same change in momentum, delivered over more time, needs far less force.

ForceNewtons, averaged over the contact time.Contact timeSeconds. A millisecond reading has to be divided by a thousand first.Object massKilograms, used to turn the impulse into a velocity change.

Impulse

100

Velocity change: 50
Acceleration: 100
Kinetic energy gained: 2,500

Values update as you type. This calculator covers the single scenario its formula assumes — see Common Mistakes for what it leaves out.

The formula this calculator uses

impulse = force x time

J: Impulse, in newton seconds
F: Force applied, in newtons
t: Time the force acts, in seconds

How to check the result by hand

1
Identify the force and how long it acts
Both matter equally. A large force applied for a tiny fraction of a second can deliver less impulse than a modest force held for a while.
2
Convert the time to seconds
Milliseconds divide by a thousand. Collisions are often quoted in milliseconds, and forgetting that conversion makes the impulse a thousand times too large.
3
Multiply force by time
Two hundred newtons for half a second is one hundred newton seconds. This is the total momentum change the object will experience.
4
Divide by the mass to get the velocity change
One hundred newton seconds on a two kilogram object changes its speed by fifty metres per second. Heavier objects change velocity less for the same impulse.
5
Check the direction of the change
A rebound reverses momentum, so the change is the sum of the incoming and outgoing amounts, not their difference. Bouncing off a wall delivers a larger impulse than sticking to it.

For worked examples, common mistakes and the limits of this formula, read the full How To Calculate Impulse page.