1. The problem statement, all variables and given/known data I have a question about this. I will post it once I fully understand my problem with this. 2. Relevant equations F *t = dp 3. The attempt at a solution At the beginning i just want to know how a collision happen. So if two object with different velocities collide with each other (They are moving towards each other. Presume that both of them will move in the same direction after the collision.) So of course one of them will lose momentum and the other will gain momentum in that direction. So my conflict here, Is how long do the forces exert on these objects? so I thought the objects exert these forces on each other because of their tendency to move in their direction. As a result, when the objects have the same velocity in the same direction, they won't have to exert these forces on each other. But this concept is wrong because that doesnt happen in real life. When two objects collide they don't always have the same velocity. So what actually happens?