Momentum is a property of motion that is classical physics is a vector (directional) quantity that in closed systems is conserved during collisions. In Newtonian physics momentum is measured as the product of the mass and component velocity of a body. For massless particles (e.g., photons) moving at the speed of light (v = c) the momentum (p) is equal to Planck's constant divided by the wavelength.

The first formal definitions and measurement of momentum date to the writing of French philosopher René Descartes (1596-1650). Descartes intended momentum to a quantifiable and measurable concept related to what he termed the "amount of motion".

Measurement of momentum often concentrates on rates of change in the momentum of bodies. In accord with the law of inertia, a body with no net force acting upon it experiences no change in momentum and therefore measurement of momentum reflect that...