Momentum Calculator

Momentum is mass times velocity, and it is the quantity conserved in a collision. Kinetic energy generally is not — some of it goes into deforming metal and heating the air — which is why two cars that bounce apart and two that crumple together obey the same momentum arithmetic and produce very different outcomes for the people inside.

The distinction between momentum and energy is worth holding onto, because they scale differently. Momentum rises in proportion to velocity; kinetic energy rises with its square. A heavy slow object and a light fast one can carry identical momentum while differing enormously in energy — which is why a lorry at walking pace and a bullet are not comparable hazards despite the arithmetic.

The impulse figure is the same number read as a change rather than a state: to stop something, you must remove all of its momentum, and impulse is force multiplied by the time you take doing it. That product is fixed, so the only variable is how long you spread it over.

Which is the entire principle behind crumple zones, airbags, crash mats and bending your knees when you land. Stopping in a tenth of a second rather than a full second needs ten times the force, and the tool shows both so the relationship is visible rather than asserted.