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Momentum is the product of the mass of a particle and its velocity. Isaac Newton's second law of motion states that the time rate of change of momentum is proportional to the force acting on the particle.

From Newton's second law it follows that, if a constant force acts on a particle for a given time, the product of force and the time interval (the impulse) is equal to the change in the momentum. Conversely, the momentum of a particle is a measure of the time required for a constant force to bring it to rest.