Impulse is the force-time product that changes an object's momentum, J = F·Δt = Δp. Drag the sliders below to set two masses, two velocities and a contact time, and watch momentum, impulse and force respond together.
Your car is doing 30 and you have to stop. Whether you brake gently or slam into a wall, your change in momentum is identical — the same Δp either way. What differs is the time you take to lose it. That is the whole idea behind impulse: J = F·Δt = Δp. Momentum p = m·v is what you carry; impulse is what you must deliver to change it, and it equals that momentum change exactly (the impulse-momentum theorem, J = m·Δv).
Now rearrange for force: F = Δp/Δt. Force is the rate at which momentum changes, so the same Δp can arrive as a huge force over a blink, or a gentle force spread across a long moment. Drag the Time slider up and watch the force readout fall while the impulse stays fixed. That single relationship explains airbags, crumple zones, and bending your knees on landing — each one stretches Δt to shrink F. Push Time down and the force spikes: the sudden stop is the one that breaks bones.
In an isolated collision the total momentum is conserved, and the two bodies trade equal, opposite impulses. Set Mass A, Velocity A, Mass B and Velocity B, then read each p, J and F side by side. For a numeric check drop values into the impulse calculator, or explore two carts meeting in the momentum lab and the rest of the interactive physics collection.
Impulse is force multiplied by the time it acts, J = F·Δt, and it equals the change in momentum, Δp. Its units are newton-seconds (N·s), the same as momentum.
It states that the impulse on an object equals its change in momentum: F·Δt = Δp = m·Δv. A force acting over a time interval changes how much momentum an object carries.
Because they extend the time Δt over which momentum changes. Since F = Δp/Δt, spreading the same change in momentum over a longer time lowers the peak force on the body.
Yes. In an isolated system with no external force, the total momentum before a collision equals the total after. The two bodies exert equal and opposite impulses on each other.