Momentum Calculator

Momentum is a measure of how hard it is to stop a moving object -- it's the product of an object's mass and its velocity, p = mv, expressed in kilogram-meters-per-second (kg*m/s). Unlike kinetic energy, which scales with the SQUARE of velocity, momentum scales linearly with both mass and velocity: doubling either one exactly doubles the momentum. That linear relationship is what makes momentum so useful in collision analysis -- in a closed system with no external forces, total momentum is conserved before and after EVERY collision, elastic or not.

That's exactly why momentum itself can't tell elastic and inelastic collisions apart: comparing the sum of ½mv² (kinetic energy) before and after is what actually reveals whether a collision was elastic, inelastic, or something in between, since kinetic energy is conserved only in an elastic collision. Momentum is also the quantity that connects directly to force through impulse: impulse (force multiplied by the time it acts) equals the CHANGE in momentum, which is the physical basis for why crumple zones, airbags, and padded landings work -- they extend the time over which a given momentum change happens, which lowers the peak force involved. This calculator computes the straightforward scalar magnitude p = mv; a full vector treatment (accounting for direction) is needed for problems involving objects moving at angles to each other.