The product of an object's mass and velocity in vector form is called its linear momentum. You can use momentum to predict the effects of collisions. If you have ever played a game of pool or billiards, you probably have a feel for how momentum works. You will come accross two types of collisions here. In elastic collisions, the objects do not stick together, while in inelastic collisions, they do. The actual definitions add some other important factors dealing with energy, but for now, these will help you visualize the collisions.