Momentum Calculator

In short Momentum is mass times velocity: 2 kg moving at 3 m/s has 6 kg·m/s of it, and 9 joules of kinetic energy. Those two numbers describe the same motion and behave completely differently, which is the single most useful thing on this page. Momentum goes as v and energy as v². Double the speed and momentum doubles while energy quadruples — so a 60 km/h crash carries four times the energy of a 30 km/h one, not twice, and stopping distance grows with the square of speed rather than in step with it. Momentum also has a direction, so a negative velocity gives negative momentum, and that sign is what makes collision arithmetic work when things move opposite ways. Energy has no direction at all, which is why two cars meeting head-on have zero total momentum and a great deal of energy to dispose of. The practical form is impulse: force times time equals change in momentum. Rearranged, the force needed to stop something is its momentum divided by the stopping time — so doubling the time halves the force. That single relationship is the entire principle behind crumple zones, airbags, crash mats and bending your knees when you land: none of them reduce the momentum you have to lose, they just spread it over more time.