# Calculating momentum before and after a collision

by sdoyle1
Tags: collision, momentum
 P: 1,135 Calculating momentum before and after a collision Momentum of a particle is defined as the product of the mass and velocity of an object. The law you will have to use here is the "Law of Conservation of Momentum." It says that for a system, if net external force acting on it is 0, total momentum will remain constant. Newton's second law (in original form) is: $F = - \frac{dp}{dt}$ If p is constant, F=0.