The document discusses linear momentum, impulse, and the conservation of momentum during collisions. It defines linear momentum as the product of an object's mass and velocity. It also states that the time rate of change of linear momentum is equal to the net force acting on an object. Impulse is defined as the force acting on an object times the change in momentum. The document outlines elastic collisions, in which both momentum and kinetic energy are conserved, and inelastic collisions, where kinetic energy is not conserved though momentum remains conserved. It provides examples of calculating momentum and velocities before and after both perfectly inelastic and elastic collisions.