Momentum Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/9/2026
Momentum is calculated with p = mass × velocity. A 2 kg object moving at 5 m/s has a momentum of 10 kg·m/s.
Explanation
Momentum is a vector quantity that combines an object's mass and velocity to quantify "how much motion" it carries — a heavy object thrown slowly can have the same momentum as a light object thrown quickly. Its importance comes from a fundamental conservation law: in an isolated system (with no external force), total momentum is always conserved, which lets you calculate, for instance, the speeds after a collision between two objects without knowing the details of the forces involved during the impact. The sign of the velocity (and therefore of momentum) indicates the direction of motion: a negative velocity simply signals movement opposite to the chosen convention, not a physical error. Momentum is what a force applied over time actually changes, a relationship our Newton's second law calculator computes from the other direction (force from mass and acceleration) rather than from a change in momentum directly.
Example: a 2 kg mass at 5 m/s
Inputs
Mass: 2 kg. Velocity: 5 m/s.
Calculation
Momentum = 2 × 5 = 10 kg·m/s.
Result
This object has a momentum of 10 kg·m/s.
Frequently asked questions
Why can momentum be negative?
Because velocity is a quantity with a direction, not just a magnitude: a negative velocity simply means the object is moving opposite to the direction chosen as positive by convention. Momentum inherits this sign, which lets you correctly calculate, for example, the total momentum of two objects moving in opposite directions (it can then be smaller than if both were moving the same way).
What is the difference between momentum and kinetic energy?
Both quantities depend on mass and velocity, but differently: momentum is proportional to velocity (p = mv), while kinetic energy is proportional to the square of velocity (Ec = ½mv²). Doubling the velocity doubles the momentum, but quadruples the kinetic energy — an essential difference in road safety, for example.
What is this quantity actually used for?
Momentum is central to analyzing collisions and impacts (traffic accidents, contact sports, rocket propulsion), thanks to the law of conservation of total momentum in an isolated system, which lets you predict speeds after an impact without knowing the details of the internal forces exchanged during it.